IX. GEOGRAPHICAL DISTRIBUTION

IX. GEOGRAPHICAL DISTRIBUTION

(§§ 226-240.)

226. Universal Marine Distribution.--Radiolaria occur in all the seas of the world, in all climatic zones and at all depths. Probably under normal conditions they always float freely in the water, whether their usual position be at the surface (pelagic), or at a certain depth (zonarial), or near to the bottom of the sea (abyssal). This appears both from numerous direct observations, as well as from conclusions which may be drawn from their organisation (and especially their promorphology) regarding their floating life (compare §§ 40-50, 219, 220). Hitherto no observation has been recorded, which justifies the assumption that Radiolaria live anywhere upon the bottom of the sea (on stones, Algæ, or other firm substances), either sessile or creeping. They perform the latter action, however, when they fall accidentally upon a firm basis or are accidentally placed upon it, but they seem normally always to float freely in the water with pseudopodia radiating in all directions. Active free-swimming movements are only met with in the case of the flagellate zoospores (§ 142). The development of Radiolaria in large masses is very remarkable (see note A), and in many parts of the ocean is so great that they play an important part in the economy of marine life, especially as food for other pelagic and abyssal animals (see note B). Medium salinity of the water seems to be most favourable to their development in masses, although it is not unknown in seas of high and low salinity (see note C). There are no Radiolaria in fresh water (see note D).

A. The development of Radiolaria takes place in many parts of the ocean in astonishingly large masses on the surface, in different strata, and near the bottom. The #Collodaria# (and especially the Sphærozoida) often cover the surface of the sea in millions, and form a shining layer, phosphorescent in the dark like the Noctilucæ, as I observed in 1859 in the Strait of Messina, in 1866 at the Canaries, and in 1881 in the Indian Ocean. Similar masses of Sphærozoum and Acanthometron were seen by Johannes Müller on the French and Ligurian coasts (L. N. 12), and John Murray found another in the Gulf Stream, off the Færöe Islands, from the surface to a depth of 600 fathoms; considerable masses of large PHÆODARIA live there also.

B. The alimentary canal of Medusæ, Salpæ, Crustacea, Pteropoda, and many other pelagic animals is a rich field for the discovery of Radiolaria, and many of the species hereinafter described are from such sources. Fossil coprolites too (e.g., those from the Jura) often contain many Polycystina.

C. Some ACANTHARIA (#Acanthometra#) and PHÆODARIA (species of Mesocena and Dictyocha) {cxlvii}live in the Baltic; I found their skeletons in the alimentary canal of Aurelia, Ascidians and Copepods.

D. The so-called "fresh-water Radiolaria," which have been described by Focke, Greeff, Grenacher and others, are all Heliozoa, without either central capsule or calymma.

227. Local distribution.--As regards their local distribution and its boundaries the Radiolaria show in general the same relations as other pelagic animals. Since they are only to a very slight extent, if at all, capable of active horizontal locomotion, the dispersion of the different species from their point of development (or "centre of creation") is dependent upon oceanic currents, the play of winds and waves and all the accidental causes which influence the transport of pelagic animals in general. These passive migrations are here, however, as always, of the greatest significance, and bring about the wide distribution of individual species in a far higher degree than any active wanderings could do. Any one who has ever followed a stream of pelagic animals for hours and seen how millions of creatures closely packed together are in a short time carried along for miles by such a current, will be in no danger of underestimating the enormous importance of marine currents in the passive migration of the fauna of the sea. Such constant currents may, however, be recognised both near the bottom of the sea and at various depths, as well as at the surface, and are therefore of just as much significance for the abyssal and zonarial as for the pelagic Radiolaria. It is easy to explain by this means how it is that so many animals of this class (probably indeed the great majority) have a wide range of distribution. The number of cosmopolitan species which live in the Pacific, Atlantic and Indian Oceans is already relatively large. In each of these three great ocean basins, too, many species show a wide distribution. On the other hand, there are very many species which are hitherto known only from one locality, and probably many small local faunas exist, characterised by the special development of particular groups. The observations which we at present possess are too incomplete, and the rich material of the Challenger is too incompletely worked out, to enable any definite conclusions to be drawn regarding the local distribution of Radiolaria.

The statements made in the systematic portion of this Report regarding the distribution of the Challenger Radiolaria are very incomplete. In most cases only one locality is mentioned, and that is the station (§ 240) in the preparations or bottom deposit from which I first found the species in question. Afterwards I often found the same species again in one or more additional stations (not seldom in numerous preparations both from the Pacific and Atlantic), without the possibility of adding them to the habitat recorded under the description. The necessary accurate determination and identification of the species (measuring the different dimensions, counting the pores, &c.), would have occupied too much time, and the writing of this extensive Report would have lasted not ten but twenty or thirty years.

228. Horizontal Distribution.--From the extensive collections of the Challenger and from the other collections which have furnished a welcome supplement to them, it appears {cxlviii}that Radiolaria are distributed throughout all seas without distinction of zones and physical conditions, even though these latter may be the cause of differences in their qualitative and quantitative development. In the case of the Radiolaria as well as of many other classes of animals, the law holds good that the richest development of forms and the greatest number of species occurs between the tropics, whilst the frigid zones (both Arctic and Antarctic) exhibit great masses of individuals, but relatively few genera and species (see note A). In the Challenger collection the greatest abundance of species of Radiolaria is exhibited by those preparations which were collected at low latitudes in the immediate neighbourhood of the equator; this is true both of the Atlantic (Stations 346 to 349) and of the Pacific (Stations 266 to 274); in the former the richest of all is Station 347 (lat. 0° 15' S.), in the latter Station 271 (lat. 0° 33' S.) (see note B). From the tropics the abundance of species seems to diminish regularly towards the poles, and more rapidly in the northern than in the southern hemisphere; the latter also appears, considered as a whole, to possess more species than the former. A limit to the life of the Radiolaria towards the poles has not yet been found; the expeditions towards the North Pole (see note C), like those towards the South (see note D), have obtained bottom-deposits and ice enclosures which contained Radiolaria; in some of the most northerly and most southerly positions which were reached the number of Radiolaria enclosed in the ice was relatively great.

A. The greater abundance of Radiolaria in the tropical seas is probably to be explained by the more favourable conditions of existence, and in particular the larger quantity of nutritive material (especially of decayed animals) and not by the higher temperature of the surface, for at depths of from 2000 to 3000 fathoms where the abyssal Radiolaria live, the temperature is but little above the freezing point or even below it (compare the bottom temperatures in the list of Challenger Stations, § 240).

B. Station 271 of the Challenger Expedition, situated almost on the equator in the Mid Pacific (lat. 0° 33' S.), exceeds all other parts of the earth, hitherto known, in respect of its wealth in Radiolaria, and this is true of the pelagic as well as of the zonarial and abyssal forms. In the Station List the deposit at this point is stated to be "Globigerina ooze"; but after the calcareous matter has been removed by means of acid, the purest Radiolarian ooze remains, rich in varied and remarkable species. More than one hundred new species have been described from this Station alone.

C. Regarding the Arctic Radiolaria compare the contributions of Ehrenberg (L. N. 24, pp. 138, 139, 195) and Brady on the English North Polar Expedition, 1875-76 (Ann. and Mag. Nat. Hist., 1878, vol. i. pp. 425, 437).

D. Regarding the Antarctic Radiolaria, compare § 230, note A, and Ehrenberg, Mikrogeologie (L. N. 6, Taf. xxxv., A.), also L. N. 24, pp. 136-139.

229. Fauna of the Pacific Ocean.--From the splendid discoveries of the Challenger, and the supplementary observations obtained from other sources, the Pacific seems to be the ocean basin which is richest both quantitatively and qualitatively in Radiolarian life, {cxlix}excelling both the Indian and Atlantic Oceans in this respect. It may be assumed with great probability that by far the largest portion of the Pacific has a depth of between 2000 and 3000 fathoms, and that its bottom is covered either with Radiolarian ooze (§ 237) or with a red clay (§ 239), which contains many SPUMELLARIA and NASSELLARIA, and has probably been derived for a great part from broken down and metamorphosed Radiolarian ooze (see note A). Pure Radiolarian ooze was found by the Challenger eastwards in the Central Pacific (over a wide area between lat. 12° N. and 12° S., Stations 265 to 274), and also westwards in the latitude of the Philippines, twenty degrees to the east of them (between lat. 5° N. and 15° N.). The great abundance of Radiolaria present in the neighbourhood of the Philippines and in the Sunda Sea was already known from other investigations (note B). The red clay also, which covers a great part of the bottom of the North Pacific, and which was obtained of very constant composition by the Challenger between lat. 35° N. and 38° N., from Japan to the meridian of Honolulu (from long. 144° E. to 156° W.), is so pre-eminently rich in Radiolaria that it often approaches in composition the Radiolarian ooze, and has probably been derived from it. The track of the Challenger through the tropical and northern parts of the Pacific describes nearly three sides of a rectangle, which includes about half of the enormous Pacific basin, and from this as well as from other supplementary observations it may with great probability be concluded that by far the largest part of the bed of the Pacific (at least three-fourths) is covered either with Radiolarian ooze or with red clay, which contains a larger or smaller amount of the remains of Radiolaria. With this agrees also the important fact that the numerous preparations of pelagic materials and collections of pelagic animals, which were collected by the Challenger in the Pacific, almost always indicate a corresponding amount of Radiolarian life on the surface. This is true in particular also of the South Pacific, between lat. 33° S. and 40° S. (from long. 133° W. to 73° W., Stations 287 to 301); the surface of this southern region and the different bathymetrical zones were rich in new and peculiar species of Radiolaria.

A. Many specimens of bottom-deposits from the Pacific, which are entered in the Challenger lists either as "red clay" or "Globigerina ooze," contain larger or smaller quantities of Radiolaria, and the number of different species of SPUMELLARIA and NASSELLARIA which they contain is often so great that the deposit might have been almost as appropriately termed "Radiolarian ooze," e.g., Stations 241 to 245, and 270, 271 (compare §§ 236-239).

B. Pacific Radiolarian ooze was first obtained by Lieutenant Brooke (May 11, 1859) between the Philippines and Marianne Islands, from a depth of 3300 fathoms (lat. 18° 3' N., long. 129° 11' E.). Ehrenberg, who first described it, found seventy-nine different species of Polycystina in it, and reported "that their quantity and the number of different forms increased with the depth" (Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1860, pp. 466, 588, 766).

230. Fauna of the Indian Ocean.--As regards its Radiolarian fauna the Indian Ocean is the least known of the three great basins. Still the few limited spots, regarding which {cl}investigations are forthcoming, indicate a very rich development of Radiolarian life. Probably it approaches more nearly the fauna of the Pacific than that of the Atlantic, both as regards the abundance and the morphological characters of its species. The researches of the Challenger are very limited and incomplete as regards the Indian Ocean, for the expedition only just touched upon this great ocean basin (2000 to 3000 fathoms deep) at its two extremities (westwards at the Cape of Good Hope and eastwards at Tasmania), its course lying for the most part south of lat. 45° S. and extending beyond lat. 65° S. (from Station 149 to 158, south of lat. 50° S.). It is true that this portion of the South Indian Ocean was shown to contain Radiolaria everywhere, but these were more plentiful in individuals than in species. Only from Station 156 to Station 159 (between lat. 62° and 47° S., and long. 95° and 130° E.) was the bottom, which consisted partly of Diatom ooze and partly of Globigerina ooze, richer in species (see note A). The gaps left by the Challenger in the investigation of the Indian Ocean, have, however, been to some extent filled from other sources. As early as 1859 the English "Cyclops" expedition had shown that the bottom of the Indian Ocean to the east of Zanzibar (lat. 9° 37' S., long. 61° 33' W.) is covered with pure Radiolarian ooze (see note B). Also since the Tertiary rocks of the Nicobar Islands are for the most part of the same composition, and since a great abundance of Radiolaria has been shown to be present both in the east part of the ocean, between the Cocos Islands and the Sunda Archipelago (see note C), and in the northern part or Arabian Sea between Socotra and Ceylon (see note D); it may be assumed with great probability that the greater part of the basin of the Indian Ocean, like that of the Pacific, is covered either with Radiolarian ooze or with the characteristic red clay. With this agrees the richness of the surface of the Indian Ocean in Radiolaria of the most various groups, which has been more extensively demonstrated.

A. The Radiolarian fauna collected by the Challenger on the voyage from the Cape to Melbourne, shows in part, namely, from Station 156 to Station 158, very peculiar and characteristic composition; in particular, the Diatom ooze of Station 157 passes over in great part into a Radiolarian ooze, mainly composed of #Sphærellaria#. This is worthy of a more thorough investigation than I was able, owing to lack of material and time, to give it.

B. The remarkably pure Radiolarian ooze of Zanzibar, discovered by Ehrenberg in 1859, was the earliest known recent example of that deposit. It was brought up by Captain Pullen of the English man-of-war "Cyclops," from a depth of 2200 fathoms, between Zanzibar and the Seychelles, and "under a magnifying power of 300 diameters, showed at the first glance a mass of almost pure Polycystina, such as no sample of a deep-sea deposit has hitherto shown. It is very noticeable that in the whole of this mass of living forms, no calcareous shells are to be seen" (Ehrenberg, L. N. 24, pp. 148, 149).

C. For the most important material from the Indian Ocean, I am indebted to Captain Heinrich Rabbe of Bremen, who during many voyages in the Indian Ocean, in his ship "Joseph Haydn," made numerous collections in different localities with the tow-net and the trawl, and admirably preserved the rich collections thus made. The greatest abundance of Radiolaria was found in those {cli}obtained to the east of Madagascar, and next in those from the neighbourhood of the Cocos Islands. I take this opportunity of expressing my thanks to Captain Rabbe for the liberality with which he placed all this valuable material at my disposal.

D. On my voyage from Aden to Bombay, and thence to Ceylon (1881), and especially on my return journey from Ceylon, between the Maldive Islands and Socotra (1882), I carried on a number of experiments with a surface net, which yielded a rich fauna of pelagic animals, and among them many new species of Radiolaria, for observation. On several nights when the smooth surface of the Indian Ocean, unrippled by any wind, shone with the most lovely phosphorescent light, I drew up water from the surface with a bucket, and obtained a rich booty. A number of other new species of Radiolaria from very various parts of the Indian Ocean I obtained from the alimentary canal of pelagic animals, such as Medusæ, Salpæ, Crustacea, &c. Although the total number of Radiolaria known to me from the Indian Ocean is much less than from the Atlantic and Pacific, there are several new genera and numerous species among them, which show that a careful study of this fauna will be of wide interest.

231. Fauna of the Atlantic Ocean.--The Atlantic Ocean in all parts, of which the pelagic fauna has been examined, has shown the same constant presence of Radiolaria, and in certain parts of its abyssal deposits a larger or smaller quantity of different types belonging to this class; on the whole, however, its Radiolarian fauna is inferior to that of the Pacific, and probably also to that of the Indian Ocean, both in quantity and quality. Pure Radiolarian ooze, such as is so extensively found on the floor of the Pacific, and in certain places in that of the Indian Ocean, has not yet been found in the Atlantic (see § 237). The red clay, too, of the deep Atlantic does not seem to be so rich in Radiolaria as that of the Pacific; nevertheless, the number of species peculiar to the Atlantic is very large, and at certain points the abundance of species as well as of individuals seems to be scarcely less than in the Pacific. This is especially true of the eastern equatorial zone not far from Sierra Leone, Stations 347 to 352 (see note A); also of the South Atlantic between Buenos Ayres and Tristan da Cunha, Stations 324, 325, 331 to 333 (see note B); and, lastly, in the North Atlantic in the Gulf Stream and near the Canary Islands (see note C). The fauna of the latter agrees for the most part with that of the Mediterranean (see note D). In addition to the material collected by the Challenger, other deep-sea investigations have furnished bottom-deposits from different parts of the ocean, which have proved very rich in Radiolaria (see note E). Furthermore, since the island of Barbados consists for the most part of fossil Radiolarian ooze, it is very probable that at certain parts of the tropical Atlantic true Radiolarian ooze, like that of the Pacific and Indian Oceans, will eventually be found in depths between 2000 and 3000 fathoms, perhaps over a considerable area.

A. The tropical zone of the eastern Atlantic seems to be especially rich in peculiar Radiolaria of different species. This is shown by numerous preparations from the surface, and from various depths (between lat. 3° S. and 11° N., and long. 14° W. to 18° W.), which were made towards the {clii}end of the cruise. Unfortunately no bottom-deposits were obtained from the most important stations (except Nos. 346 and 347, depths 2350 and 2250 fathoms) in this region; at these the deposit was a Globigerina ooze containing numerous different species of Radiolaria.

B. In the South Atlantic, between Buenos Ayres and Tristan da Cunha (between lat. 35° S. and 43° S., long. 8° W. and 57° W.) there appears to be a long stretch covered partly with Globigerina ooze (Stations 331 to 334), or red clay (Stations 329, 330), partly with blue mud (Stations 318 to 328), which contains not only large masses of individuals but numerous peculiar species of SPUMELLARIA and NASSELLARIA. The preparations from the surface-takings of this region are also rich in these, as well as in peculiar PHÆODARIA.

C. The northern part of the Atlantic appears on the whole to be inferior to the tropical and southern portions as regards its richness in Radiolaria, and from the western half more especially, only few species are known. From my researches at Lanzerote in 1866-67, it appears that the pelagic fauna of the Canary Islands is very rich in them, as is also the Gulf Stream in the neighbourhood of the Færöe Channel, according to the investigations of John Murray (see his Report on the "Knight-Errant" Expedition, Proc. Roy. Soc. Edin., vol. xi., 1882).

D. The Radiolaria of the Mediterranean are of special interest, because almost all our knowledge of these organisms in the living conditions and of their vital functions has been derived from investigations conducted on its shores. Johannes Müller laid the foundation of this knowledge by his investigations at Messina, and on the Ligurian and French coasts at Nice, Cette, and St. Tropez (L. N. 10). The many new Radiolaria which I described in my Monograph (L. N. 16, 1862), were for the most part taken at Messina, the place which possesses a richer pelagic fauna than any other, so far as is yet known, in the Mediterranean. Other new species I found afterwards at Villafranca near Nice, in 1864 (L. N. 19), at Portofino near Genoa (1880), at Corfu (1877), and at other points on the coast. In Messina also, Richard Hertwig collected the material for his valuable treatise on the Organisation of the Radiolaria (L. N. 33), after he had previously made investigations into their histology at Ajaccio in Corsica (L. N. 26). Lastly, at Naples, Cienkowski (L. N. 22) and Karl Brandt (L. N. 38, 39, 52) carried out their important investigations into the reproduction and symbiosis of the Radiolaria. With respect to the character of its Radiolaria, the Mediterranean fauna is to be regarded as a special province of the North Atlantic.

E. Among the smaller contributions which have been made towards our knowledge of the Atlantic Radiolarian fauna, the communications of Ehrenberg on the deposits obtained in sounding for the Atlantic cable, and on the Mexican Gulf Stream near Florida, deserve special mention (L. N. 24, pp. 138, 139-145).

232. Vertical Distribution.--The most important general result of the discoveries of the Challenger, as regards the vertical or bathymetrical distribution of the Radiolaria, is the interesting fact that numerous species of this class are found living at the most various depths of the sea, and that certain species are limited to particular bathymetrical zones, i.e., are adapted to the conditions which obtain there. In this respect three different Radiolarian faunas may be distinguished, which may be shortly termed "pelagic," "zonarial," and "abyssal." The pelagic Radiolaria swim at the surface, and when they sink (e.g., in a stormy sea), only descend to a small depth, probably not more than from {cliii}20 to 30 fathoms (§ 233). The complicated conditions of existence created by the keen struggle for existence at the surface of the sea, give rise to the formation of very numerous pelagic species, especially of Porulosa (SPUMELLARIA and ACANTHARIA). The abyssal Radiolaria are very different from those just mentioned; they live at the bottom of the deep-sea, not resting upon nor attached to it, but probably floating at a little distance above it, and are adapted to the conditions of existence which obtain there (§ 235). Here the Osculosa (NASSELLARIA and PHÆODARIA) seem to predominate. The zonarial Radiolaria live floating at various depths between the pelagic and abyssal species (§ 234). In their morphological characters they gradually approach the pelagic forms upwards and the abyssal downwards.

The views which have hitherto been held regarding the bathymetrical or vertical distribution of the Radiolaria have been entirely altered by the magnificent discoveries of the Challenger, and especially by the important observations of Sir Wyville Thomson (L. N. 31) and John Murray (L. N. 27). These two distinguished deep-sea explorers have, as a result of their wide experience, been convinced that Radiolaria exist at all depths of the ocean, and that there are large numbers of true deep-sea species which are never found at the surface of the sea nor at slight depths (L. N. 31, vol. i. pp. 236-238; L. N. 27, pp. 523, 525). The result of my ten years' work upon the Challenger Radiolaria, and the comparative study of more than a thousand mountings from all depths, has only been to confirm this opinion, and I am further persuaded that it will some day be possible by the aid of suitable nets (not yet invented) to distinguish different faunistic zones in the various depths of the sea. In this connection may be mentioned the specially interesting fact that the species of Radiolaria of one and the same family present in the different depths characteristic morphological distinctions, which obviously correspond to their different physiological relations in the struggle for existence. Owing to those extensive discoveries, the representation which I gave in my Monograph (1862, L. N. 16, pp. 172-196) of the vertical distribution of the Radiolaria, and of their life in the greatest depths of the sea, has been entirely changed. Compare also Bütschli (L. N. 41, p. 466).

233. The Pelagic Fauna.--The surface of the open ocean seems everywhere, at a certain distance from the coast at least, to be peopled by crowds of living Radiolaria. In the tropical zone these pelagic crowds consist of many different species, whilst in the frigid zones, on the other hand, they are made up of many individuals belonging to but few species. Most of these inhabitants of the surface may be regarded as truly pelagic species, which either remain always at the surface or descend only very slightly below it. Probably most Porulosa (both SPUMELLARIA and ACANTHARIA) belong to this group; whilst but few Osculosa occur in it, and fewer PHÆODARIA than NASSELLARIA. In general the pelagic Radiolaria are distinguished from the abyssal by the more delicate and slender structure of their skeletons; the pores of the lattice-shells are larger, the intervening trabeculæ thinner; the armature of spines, spathillæ, anchors, &c., is more various and more highly developed. Numerous forms are to be found among the pelagic {cliv}Radiolaria which have either an incomplete skeleton or none at all. When the pelagic forms leave the surface on account of unfavourable weather, they appear only to sink to slight depths (probably not below 20 or 30 fathoms). Within the limits of the same family the size of the pelagic species seems to be on an average greater than that of the related abyssal forms.

234. The Zonarial Fauna.--Between the pelagic fauna living at the surface of the open sea and the abyssal, which floats immediately over the bottom, there appears to be usually a middle fauna, which inhabits the different bathymetrical zones of the intermediate water, and hence may be shortly called the "zonarial" fauna. The different species of Radiolaria which inhabit these different strata in the same vertical column of water present differences corresponding to those of the plants composing the several zones of vegetation, which succeed each other at different heights on a mountain; they correspond to the different conditions of existence which are presented by the different strata of water, and to which they have become adapted in the struggle for existence. The existence of such bathymetrical zones has been shown by those important, if not numerous, observations of the Challenger, in which the tow-net was used at different depths at one and the same Station. In several cases the character of the Radiolarian fauna at different depths presented characteristic differences.

For the present, and until we are better acquainted with the characters of the Radiolarian fauna at different depths, we may distinguish provisionally the following five bathymetrical zones:--(1) The pelagic zone, extending from the surface to a depth of about 25 fathoms; (2) the pellucid zone, extending from 25 to 150 fathoms, or as far as the influence of the sunlight makes itself felt; (3) the obscure zone, extending from 150 to 2000 fathoms, or from the depth at which sunlight disappears to that at which the influence of the water containing carbonic acid begins and the calcareous organisms vanish; (4) the siliceous zone, extending from 2000 or 2500 to about 3000 fathoms, in which only siliceous not calcareous Rhizopoda are found, and in which the peculiar conditions of the lowest regions have not yet appeared; (5) the abyssal zone, in which the accumulation of the oceanic deposits, and the influence of the bottom currents, create new conditions of existence. So far as our isolated and incomplete observations of the zonarial Radiolarian fauna extend, it appears that the subclass Porulosa (SPUMELLARIA and ACANTHARIA) predominates in the two upper zones, and as the depth increases is gradually replaced by the subclass Osculosa (NASSELLARIA and PHÆODARIA), so that the latter predominates in the two lowest zones. The obscure zone which lies in the middle is probably the poorest in species. In general, the morphological characters of the zonarial fauna appear to change gradually upwards into the delicate form of the pelagic and downwards into the robust constitution of the abyssal; so also the average size of the individuals (within the limits of the same family) appears to increase upwards and decrease downwards.

235. The Abyssal Fauna.--The great majority of Radiolaria which have hitherto been observed, and which are described in the systematic portion of this Report, have been obtained from the bottom of the deep-sea, and more than half of all the species have been {clv}derived from the pure Radiolarian ooze, which forms the bed of the Central Pacific at depths of from 2000 to 4000 fathoms (§ 237). Many of these abyssal forms were brought up with the malacoma uninjured, and they show, both when mounted immediately in balsam, and when preserved in alcohol, all the soft parts almost as clearly as fresh preparations of pelagic Radiolaria. These species are to be regarded as truly abyssal, i.e., as forms which live floating only a little distance above the bottom of the deep-sea, having become adapted to the peculiar conditions of life which obtain in the lowest regions of the ocean. Probably the majority of the PHÆODARIA belong to these abyssal Radiolaria, as well as a large number of NASSELLARIA, but on the other hand, only a small number of ACANTHARIA and SPUMELLARIA are found there. A character common to these abyssal forms, and rarely found in those from the surface or from slight depths, is found in their small size and their heavy massive skeletons, in which they strikingly resemble the fossil Radiolaria of Barbados and the Nicobar Islands. The lattice-work of the shell is coarser, its trabeculæ thicker and its pores smaller than in pelagic species of the same group; also the apophyses (spines, spathillæ, coronets, &c.), are much less developed than in the latter. From these true abyssal Radiolaria must be carefully distinguished those species whose empty skeletons, devoid of all soft parts, occur also in the Radiolarian ooze of the deep-sea, but are clearly only the sunken remains of dead forms, which have lived at the surface or in some of the upper zones.

236. Deposits containing Radiolaria.--The richest collection of Radiolaria is found in the deposits of ooze which form the bed of the ocean. Although the pelagic material skimmed from the surface of the sea, and the zonarial material taken by sinking the tow-net to various depths, are always more or less rich in Radiolaria, still the number of species thus obtained is, on the whole, much less than has hitherto been got merely from deep-sea deposits. Of course the skeletons found in the mud of the ocean-bed, may belong either to the abyssal species which live there (§ 235), or to the zonarial (§ 234), or to the pelagic species (§ 233), for the siliceous skeletons of these latter sink to the bottom after their death. Almost all these remains found in the deposits belong to the siliceous "Polycystina" (SPUMELLARIA and NASSELLARIA); PHÆODARIA occur but sparingly, and ACANTHARIA are entirely wanting, for their acanthin skeleton readily dissolves. The abundance of Radiolaria varies greatly according to the composition and origin of the deposits. In general marine deposits may be divided into two main divisions, terrigenous and abyssal, or, more shortly, muds and oozes. The terrigenous deposits (or muds) include all those sediments which are made up for the most part of materials worn away from the coasts of continents and islands, or brought down into the sea by rivers. Their greatest extent from the coast is about 200 nautical miles. They contain varying quantities of Radiolaria, but much fewer than those of the next group. The abyssal deposits (or oozes) usually commence at a distance of from 100 to 200 nautical miles {clvi}from the coast. In general they are characterised by great uniformity, corresponding to the constancy of the conditions under which they are laid down; they may be divided into three categories, the true Radiolarian ooze (§ 237), Globigerina ooze (§ 238), and red clay (§ 239). Of these three most important deep-sea formations the first is by far the richest in Radiolaria, although the other two contain often very many siliceous shells.

The marvellous discoveries of the Challenger have thrown upon the nature of marine deposits an entirely new light, which justifies most important conclusions regarding the geographical distribution and geological significance of the Radiolaria. Since Dr. John Murray and the Abbé Renard will treat fully of these interesting relations in a forthcoming volume of the Challenger series (Report on the Deep-Sea Deposits), it will be sufficient here to refer to their preliminary publication already published (Narrative of the Cruise of H.M.S. Challenger, 1885, vol. ii. part ii. pp. 915-926); see also the earlier communications by John Murray (1876, L. N. 27, pp. 518-537), and by Sir Wyville Thomson (The Atlantic, L. N. 31, vol. i. pp. 206-246). In the Narrative (loc. cit., p. 916) the following table of marine deposits is given:--

{Shore formations, } Found in inland {Blue mud, } seas and along the {Green mud and sand, } shores of {Red mud, } continents. Terrigenous deposits.{ {Volcanic mud and sand, } Found around oceanic {Coral mud and sand, } islands and along the {Coralline mud and sand, } shores of continents.

{Globigerina ooze, } Found in the abysmal {Pteropod ooze, } regions of the Abysmal deposits. {Diatom ooze, } ocean basins. {Radiolarian ooze, } {Red clay, }

237. Radiolarian Ooze.--By Radiolarian ooze, in the strict sense of the term, are understood those oceanic deposits, the greater part of which (often more than three-quarters) is composed of the siliceous skeletons of this class. Such pure Radiolarian ooze has only been found in limited areas of the Pacific and Indian Oceans. It is most conspicuous in the Central Pacific, between lat. 12° N. and 8° S., long. 148° W. to 152° W., the depth being everywhere between 2000 and 3000 fathoms (Stations 266 to 268 and 272 to 274). In the deepest of the Challenger soundings (Station 225, 4475 fathoms) the bottom is composed of pure Radiolarian ooze, as well as at the next Station in the Western Tropical Pacific (Station 226, 2300 fathoms), the latitude varying from 12° N. to 15° N., and the longitude from 142° E. to 144° E. In the Indian Ocean also, pure Radiolarian ooze was found in the year 1859 between Zanzibar and the Seychelles, this being the first known example of it (§ 230). On the other hand, it has not yet been found in the bed of the Atlantic; but the Tertiary formations of Barbados (Antilles, § 231) like those of the Nicobar Islands (Further India), are to be regarded as pure Radiolarian {clvii}ooze in the fossil condition. Mixed Radiolarian ooze is the name given to those deposits in which the Radiolaria exceed any of the other organic constituents, although they do not make up half the total mass. To this category belong a large number of the Challenger soundings which are entered in the Station list either as red clay or Globigerina ooze. Such mixed Radiolarian ooze has been discovered (A) in the North Pacific in an elongated area of red clay extending from Station 241 to Station 245 (perhaps even from Station 238 to Station 253), that is, at least, from long. 157° E. to 175° E., between lat. 35° N. and 37° N.; (B) in the tropical Central Pacific in the Globigerina ooze of Stations 270 and 271. The ooze from the latter station, situated almost on the equator (lat. 0° 33' S., long. 151° 34' W.), is specially remarkable, for it has yielded more new species of SPUMELLARIA and NASSELLARIA than any other Station, not excluding even the neighbouring Stations 268, 269, and 272. Probably such mixed Radiolarian ooze is very widely distributed in the depths of the ocean, as, for example, in the South Pacific (Stations 288, 289, 300, and 302), and in the Southern Ocean (Stations 156 to 159); also in the South Atlantic (Stations 324, 325, 331, 332) and in the tropical Atlantic (Stations 348 to 352). When carefully purified and decalcified by acids, Radiolarian ooze appears as a fine shining white powder; in the raw state it is yellowish or reddish, sometimes reddish-brown or dark brown in colour, according to the quantity of oxides of iron, manganese, &c., which it contains. Calcareous skeletons (especially the tests of pelagic Foraminifera) do not occur at all or only in very minute quantities in pure Radiolarian ooze from more than 2000 fathoms, whilst specimens of mixed ooze often contain considerable quantities of them.

Pure Radiolarian ooze was first described by Dr. John Murray as regards its peculiar nature and composition under the name "Radiolarian ooze" (1876, L. N. 27, pp. 525, 526); compare also Sir Wyville Thomson (The Atlantic, L. N. 31, vol. i. pp. 231-238), and John Murray (Narr. Chall. Exp., L. N. 53, vol. i. pt. ii. pp. 920-926, pl. N. fig. 2). The different specimens of pure Radiolarian ooze obtained by the Challenger from the Pacific, and handed to me for investigation, are from depths of from 2250 fathoms to 4475 fathoms, and may be divided according to their composition into three different groups:--I. The Radiolarian ooze of the Western Tropical Pacific, Stations 225 and 226, from depths of 4475 and 2300 fathoms (lat. 11° N. to 15° N., and long. 142° E. to 144° E.). II. The Radiolarian ooze of the northern half of the Central Pacific, Stations 265 to 269, from depths of 2550 to 2900 fathoms. III. The Radiolarian ooze of the southern half of the Central Pacific, Stations 270 to 274, from depths of 2350 to 2925 fathoms. A fourth group would be constituted by the Radiolarian ooze from the Philippines, which was brought up by Brooke in 1860 near the Marianne Islands from 3300 fathoms, and described by Ehrenberg (Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1860, p. 765). The Diatom ooze, too, found by the Challenger in the Antarctic regions (Stations 152 to 157) is in some parts so rich in Radiolaria that it passes over into true Radiolarian ooze. Regarding the Radiolarian ooze from Zanzibar, obtained by Captain Pullen in 1859 from 2200 fathoms (§ 230), we have only the incomplete communications of Ehrenberg (L. N. 24, p. 147). A more accurate knowledge of these deposits from the Indian Ocean, and of {clviii}those which we may with probability expect from the tropical eastern Atlantic, will be sure to increase very widely our knowledge of the class.

238. Globigerina Ooze.--Next to the Radiolarian ooze proper the Globigerina ooze is the deposit which is richest in the remains of Radiolaria. Often these are so abundant that it is doubtful to which category the specimen should be referred (e.g., Stations 270 and 271, see § 237). In fact, the two pass without any sharp boundary into each other, and both present transitions to the Diatom ooze. Next to red clay (§ 239), Globigerina ooze is the most widely distributed of all sediments, and forms a large part of the bed of the ocean at depths of 250 to 2900 fathoms (especially between 1000 and 2000 fathoms). It covers extensive areas at depths below 1800 fathoms, and in still deeper water is replaced by red clay. It is a fine-grained white, grey, or yellowish powder, which sometimes becomes coloured rose, red, or brown owing to the admixture of oxides of iron and manganese. True Globigerina ooze consists for the most part of the accumulated calcareous shells of pelagic Foraminifera, principally Globigerina and Orbulina, but also Hastigerina, Pulvinulina, &c. It contains usually from 50 to 80 per cent. of calcium carbonate, the extreme values being 40 and 95 per cent. After this has been removed by acids, there remains a residue, which consists partly of the siliceous shells of Radiolaria and Diatoms, and partly of mineral particles identical with the volcanic elements of the red clay.

Regarding the composition and significance of the Globigerina ooze, see John Murray (L. N. 27, pp. 523-525, and L. N. 53, vol. i. p. 919). Recently this author has separated from the Globigerina ooze (sensu stricto), the Pteropod ooze, distinguished from the former by the greater abundance of Pteropod shells and calcareous shells of larger pelagic organisms which it contains. It is found in moderate depths (at most 1500 fathoms), and contains fewer Radiolaria.

239. Red Clay.--This is quantitatively the most important of all deep-sea deposits, covering by far the greatest extent of the three great ocean basins at depths greater than 2200 fathoms. It thus far surpasses in area the other deposits, both Radiolaria and Globigerina oozes, and commonly forms a still deeper layer beneath them. Probably these three deep-sea deposits together cover about three-eighths of the whole surface of the earth, that is, about as much as all the continents together, whilst only two-eighths are covered by the terrigenous deposits. Red clay is principally composed of silicate of alumina, mixed in various proportions with other finely granular substances; its usual red colour, which sometimes passes over into grey or brown, is more especially due to admixture of oxides of iron and manganese. Calcareous matter is usually entirely wanting, or present only in traces, whilst free silica is found in very variable, often considerable quantities. The chief mass of the red clay consists of volcanic ashes, pumice, fragments of lava, &c., whilst a large part of it is generally composed of shells of Radiolaria or fragments of {clix}them; in many places the number of well-preserved skeletons contained in the red clay is very considerable, so that it passes over gradually into the Radiolarian ooze (e.g., in the North Pacific, Stations 238 to 253, see § 237). Hence it may be supposed that a large part of the red clay consists of decomposed Radiolarian ooze.

The characteristic composition and fundamental significance of the red clay in the formation of the deep-sea bed were first made known by the discoveries of the Challenger (compare John Murray, 1876, L. N. 27, p. 527, and Narr. Chall. Exp., L. N. 53, vol. i. pt. ii. pp. 920-926, pl. N; also Wyville Thomson, The Atlantic, L. N. 31, vol. i. pp. 226-229). The mineral components of the red clay are for the most part of volcanic origin, due to the decomposition of pumice, lava, &c. Among the organic remains found in it, the siliceous skeletons of Radiolaria are by far the most important, and their number is often considerable. A large portion of the red clay appears to me to consist of broken down Radiolarian shells, in which a peculiar metamorphism probably has taken place. Sir Wyville Thomson was of opinion that a considerable proportion of it consisted of the remains of Globigerina ooze, the calcareous constituents of which had been removed by the carbon dioxide in the deep-sea water (L. N. 31, loc. cit.). Among these remains, however, the siliceous skeletons of the Radiolaria play a significant and often the most important part. Furthermore, John Murray has called attention to the fact that in many deep-sea deposits yellow and red insoluble particles remain, which unmistakably present the form of Radiolarian shells (L. N. 27, p. 513). At Station 303 he found "amorphous clayey matter, rounded yellow minerals, many Radiolaria-shaped;" at Station 302 there was sediment "consisting almost entirely of small rounded red mineral particles; many of these had the form of both Foraminifera and Radiolaria; and it seemed as if some substance had been deposited in and on these organisms." Similar transitions from well-preserved Radiolarian shells into amorphous mineral particles I have found in several other specimens of Challenger soundings, and consider them a further argument for the supposition that the Radiolaria often take an important share in the formation of the red clay.

240. List of Stations at which Radiolaria were observed on the Challenger Expedition.--The 168 Stations recorded below, in soundings or surface preparations from which I found Radiolaria, belong to the most various parts of the sea which the Challenger traversed during her voyage round the world; they constitute about half of the (364) observing Stations contained in the official list published in the Narrative of the Cruise (Narr. Chall. Exp., vol. i. part ii. Appendix ii.).

In addition to the particulars given in the list regarding the geographical position of the Station, depth, temperature, and composition of the bottom deposit, I have added the result of my investigations as regards the relative abundance of the Radiolaria in each. The five letters (A to E) denote the following degrees of frequency:--A, abundant Radiolaria (AI, pure Radiolarian ooze; AII, mixed Radiolarian ooze); B, very numerous Radiolaria (but not a predominating quantity); C, many Radiolaria (medium quantity); D, few Radiolaria; E, very few Radiolaria (as they occur almost always). In using these symbols regard has been had to abundance of the abyssal as well as of the zonarial and pelagic forms (§ 232); sometimes also the estimated number of Radiolaria has been inserted, based upon information given by John Murray in his Preliminary Report (L. N. 27), and in the Narrative of the Cruise (L. N. 53), as well as by Henry B. Brady in his Report on the {clx}Foraminifera (Zool. Chall. Exp., part xxii., 1884). From Stations 348 to 352 in the Eastern Tropical Atlantic no specimens of the bottom were obtained, but a rich pelagic Radiolarian fauna was demonstrated by numerous preparations from the surface. The depths are given in fathoms and the temperature in degrees Fahrenheit. In the column describing the nature of the bottom the following abbreviations are used:--

rad. oz. = Radiolarian ooze (§ 237). gl. oz. = Globigerina ooze (§ 238). r. cl. = red clay (§ 239). pt. oz. = Pteropod ooze (see p. clviii). di. oz. = Diatom ooze (see p. clvii). bl. m. = blue mud, } terrigenous deposits gr. m. = green mud, } (see p. clvi). volc. m. = volcanic mud, } r. m. = red mud.

+----------+-----------+--------+------------+-----------+--------------+ | | | | Bottom | | Relative | |Challenger| Locality. |Depth in|Temperature,| Nature of | Abundance of | | Station. | |Fathoms.| ° F. | Bottom. | Radiolaria. | +----------+-----------+--------+------------+-----------+--------------+ | | | | | | | | 1. | N. Atl. | 1890 | 36.8 | gl. oz. | D few | | 2. | " | 1945 | 36.8 | gl. oz. | E very few | | 5. | " | 2740 | 37.0 | r. cl. | D few | | 9. | " | 3150 | 36.8 | r. cl. | E very few | | 24. | Tr. Atl. | 390 | ... | pt. oz. | D few | | | | | | | | | 32. | N. Atl. | 2250 | 36.7 | gl. oz. | E very few | | 45. | " | 1240 | 37.2 | bl. m. | E " | | 50. | " | 1250 | 38.0 | bl. m. | E " | | 64. | " | 2700 | ... | r. cl. | D few | | 76. | " | 900 | 40.0 | pt. oz. | D " | | | | | | | | | 98. | Tr. Atl. | 1750 | 36.7 | gl. oz. | C many | | 106. | " | 1850 | 36.6 | gl. oz. | C " | | 108. | " | 1900 | 36.8 | gl. oz. | C " | | 111. | " | 2475 | 33.7 | gl. oz. | C " | | 120. | " | 675 | ... | r. m. | D few | | | | | | | | | 132. | S. Atl. | 2050 | 35.0 | gl. oz. | C many | | 134. | " | 2025 | 36.0 | gl. oz. | C " | | 137. | " | 2550 | 34.5 | r. cl. | D few | | 138. | " | 2650 | 35.1 | r. cl. | D " | | 143. | S. Ind. | 1900 | 35.6 | gl. oz. | E very few | | | | | | | | | 144. | " | 1570 | 35.8 | gl. oz. | E " | | 145. | " | 140 | ... | volc. s. | D few | | 146. | " | 1375 | 35.6 | gl. oz. | C many | | 147. | " | 1600 | 34.2 | di. oz. | C " | | 148. | " | 210 | ... {| gravel, } | D few | | | | | {| shells } | | | | | | | | | | 149H. | " | 127 | ... | volc. m. | D " | | 150. | " | 150 | 35.2 | gravel | D " | | 151. | " | 75 | ... | volc. m. | D " | | 152. | " | 1260 | ... | di. oz. | C many | | 153. | " | 1675 | ... | bl. m. | C " | | | | | | | | | 154. | " | 1800 | ... | bl. m. | C " | | 155. | " | 1300 | ... | bl. m. | C " | | 156. | " | 1975 | ... | di. oz. | B numerous | | 157. | " | 1950 | 32.1 | di. oz. | B " | | 158. | " | 1800 | 33.5 | gl. oz. | B " | | | | | | | | | 159. | " | 2150 | 34.5 | gl. oz. | B " | | 160. | " | 2600 | 33.9 | r. cl. | C many | | 162. | " | 38 | ... | sand | E very few | | 163. | S. Pac. | 2200 | 34.5 | gr. m. | E " | | 164A. | " | 1200 | ... | gr. m. | E " | | | | | | | | | 165. | S. Pac. | 2600 | 34.5 | r. cl. | D few | | 166. | " | 275 | 50.8 | gl. oz. | D " | | 169. | " | 700 | 40.0 | bl. m. | D " | | 175. | Tr. Pac. | 1350 | 36.0 | gl. oz. | E very few | | 181. | " | 2440 | 35.8 | r. cl. | E " | | | | | | | | | 193. | " | 2800 | 38.0 | bl. m. | D few | | 195. | " | 1425 | 38.0 | bl. m. | C many | | 197. | " | 1200 | 35.9 | bl. m. | D few | | 198. | " | 2150 | 38.9 | bl. m. | C many | | 200. | " | 250 | ... | gr. m. | B numerous | | | | | | | | | 201. | " | 82 | ... | st. & gra.| C many | | 202. | " | 2550 | 50.5 | bl. m. | B numerous | | 205. | " | 1050 | 37.0 | bl. m. | C many | | 206. | " | 2100 | 36.5 | bl. m. | B numerous | | 211. | " | 2225 | 50.5 | bl. m. | B " | | | | | | | | | 213. | " | 2050 | 38.8 | bl. m. | C many | | 214. | " | 500 | 41.8 | bl. m. | C " | | 215. | " | 2550 | 35.4 | r. cl. | C many | | 216A | " | 2000 | 35.4 | gl. oz. | B numerous | | 217. | " | 2000 | 35.2 | bl. m. | C many | | | | | | | | | 218. | " | 1070 | 36.4 | bl. m. | C " | | 220. | " | 1100 | 36.2 | gl. oz. | C " | | 221. | " | 2650 | 35.4 | r. cl. | B numerous | | 222. | " | 2450 | 35.2 | r. cl. | B " | | 223. | " | 2325 | 35.5 | gl. oz. | B " | | | | | | | | | 224. | " | 1850 | 35.4 | gl. oz. | B " | | 225. | " | 4475 | 35.2 | rad. oz. | A very many | | 226. | " | 2300 | 35.5 | rad. oz. | A " | | 230. | N. Pac. | 2425 | 35.5 | r. cl. | C many | | 231. | " | 2250 | 35.2 | bl. m. | C " | | | | | | | | | 232. | " | 345 | 41.1 | gr. m. | C " | | 234. | " | 2675 | 35.8 | bl. m. | B numerous | | 235. | " | 565 | 38.1 | gr. m. | D few | | 236. | " | 775 | 37.6 | gr. m. | C many | | 237. | " | 1875 | 35.3 | bl. m. | C " | | | | | | | | | 238. | " | 3950 | 35.0 | r. cl. | B numerous | | 239. | " | 3625 | 35.1 | r. cl. | B " | | 240. | " | 2900 | 34.9 | r. cl. | B " | | 241. | " | 2300 | 35.1 | r. cl. | A very many | | 242. | " | 2575 | 35.1 | r. cl. | AII " | | | | | | | | | 243. | " | 2800 | 35.0 | r. cl. | AII " | | 244. | " | 2900 | 35.3 | r. cl. | AII " | | 245. | " | 2775 | 34.9 | r. cl. | AII " | | 246. | " | 2050 | 35.1 | gl. oz. | B numerous | | 247. | " | 2530 | 35.2 | r. cl. | C many | | | | | | | | | 248. | " | 2900 | 35.1 | r. cl. | C " | | 249. | " | 3000 | 35.2 | r. cl. | B numerous | | 250. | " | 3050 | 35.0 | r. cl. | B " | | 251. | " | 2950 | 35.1 | r. cl. | B " | | 252. | " | 2740 | 35.3 | r. cl. | B " | | | | | | | | | 253. | " | 3125 | 35.1 | r. cl. | B " | | 254. | " | 3025 | 35.0 | r. cl. | C many | | 255. | " | 2850 | 35.0 | r. cl. | C " | | 256. | " | 2950 | 35.2 | r. cl. | B numerous | | 257. | " | 2875 | 34.9 | r. cl. | C many | | | | | | | | | 258. | " | 2775 | 35.2 | r. cl. | C " | | 259. | Tr. Pac. | 2225 | 34.9 | r. cl. | C " | | 261. | " | 2050 | 35.2 | volc. m. | C many | | 262. | " | 2875 | 35.2 | r. cl. | C " | | 263. | " | 2650 | 35.1 | r. cl. | B numerous | | | | | | | | | 264. | " | 3000 | 35.2 | r. cl. | C many | | 265. | " | 2900 | 35.0 | r. cl. | A very many | | 266. | " | 2750 | 35.1 | rad. oz. | A " | | 267. | " | 2700 | 35.0 | rad. oz. | A " | | 268. | " | 2900 | 34.8 | rad. oz. | A " | | | | | | | | | 269. | " | 2550 | 35.2 | rad. oz. | A " | | 270. | " | 2925 | 34.6 | gl. oz. | A " | | 271. | " | 2425 | 35.0 | gl. oz. | A " | | 272. | " | 2600 | 35.1 | rad. oz. | A " | | 273. | " | 2350 | 34.5 | rad. oz. | A " | | | | | | | | | 274. | " | 2750 | 35.1 | rad. oz. | A " | | 275. | " | 2610 | 35.0 | r. cl. | B numerous | | 276. | " | 2350 | 35.1 | r. cl. | C many | | 280. | " | 1940 | 35.3 | gl. oz. | D few | | 281. | " | 2385 | 34.9 | r. cl. | C many | | | | | | | | | 282. | S. Pac. | 2450 | 35.1 | r. cl. | C " | | 283. | " | 2075 | 35.4 | gl. oz. | D few | | 284. | " | 1985 | 35.1 | gl. oz. | C many | | 285. | " | 2375 | 35.0 | r. cl. | D few | | 286. | " | 2335 | 34.8 | r. cl. | D " | | | | | | | | | 287. | " | 2400 | 34.7 | r. cl. | D " | | 288. | " | 2600 | 34.8 | r. cl. | B numerous | | 289. | " | 2550 | 34.8 | r. cl. | B " | | 290. | " | 2300 | 34.9 | r. cl. | C many | | 291. | " | 2250 | 34.6 | r. cl. | C " | | | | | | | | | 292. | " | 1600 | 35.2 | gl. oz. | C " | | 293. | " | 2025 | 34.4 | gl. oz. | C " | | 294. | " | 2270 | 34.6 | r. cl. | D few | | 295. | " | 1500 | 35.3 | gl. oz. | C many | | 296. | " | 1825 | 35.3 | gl. oz. | D few | | | | | | | | | 297. | " | 1775 | 35.5 | gl. oz. | D " | | 298. | " | 2225 | 35.6 | bl. m. | C many | | 299. | " | 2160 | 35.2 | bl. m. | C " | | 300. | " | 1375 | 35.5 | gl. oz. | B numerous | | 302. | " | 1450 | 35.6 | gl. oz. | B " | | | | | | | | | 303. | " | 1325 | 36.0 | bl. m. | D few | | 304. | " | 45 | ... | gr. m. | E very few | | 318. | S. Atl. | 2040 | 33.7 | bl. m. | C few | | 319. | " | 2425 | 32.7 | bl. m. | C " | | 323. | " | 1900 | 33.1 | bl. m. | C " | | | | | | | | | 324. | " | 2800 | 32.6 | bl. m. | B numerous | | 325. | " | 2650 | 32.7 | bl. m. | B " | | 326. | " | 2775 | 32.7 | bl. m. | C many | | 327. | " | 2900 | 32.8 | bl. m. | C " | | 328. | " | 2900 | 32.9 | bl. m. | B numerous | | | | | | | | | 329. | " | 2675 | 32.3 | r. cl. | C many | | 330. | " | 2440 | 32.7 | r. cl. | C " | | 331. | " | 1715 | 35.4 | gl. oz. | B numerous | | 332. | " | 2200 | 34.0 | gl. oz. | B " | | 333. | " | 2025 | 35.3 | gl. oz. | B " | | | | | | | | | 334. | " | 1915 | 35.8 | gl. oz. | C many | | 335. | " | 1425 | 37.0 | pt. oz. | D few | | 338. | Tr. Atl. | 1990 | 36.3 | gl. oz. | D few | | 340. | " | 1500 | 37.6 | pt. oz. | E very few | | 341. | " | 1475 | 38.2 | pt. oz. | E " | | | | | | | | | 342. | " | 1445 | 37.5 | pt. oz. | D few | | 343. | " | 425 | 40.3 | volc. s. | E very few | | 344. | " | 420 | ... | volc. s. | E " | | 345. | " | 2010 | 36.8 | gl. oz. | D few | | 346. | " | 2350 | 34.0 | gl. oz. | C many | | | | | | | | | 347. | " | 2250 | 36.2 | gl. oz. | B numerous | | 348. | " | (2450) | ... | (Pelag.) | B " | | 349. | " | ... | ... | (Pelag.) | B " | | 350. | " | ... | ... | (Pelag.) | B " | | 351. | " | ... | ... | (Pelag.) | B " | | | | | | | | | 352. | " | ... | ... | (Pelag.) | B " | | 353. | N. Atl. | 2965 | 37.6 | r. cl. | C many | | 354. | " | 1675 | 37.8 | gl. oz. | D few | +----------+-----------+--------+------------+-----------+--------------+

+----------+--------+-----------------------+---------------------------+ | | | | | |Challenger| Date. |Latitude and Longitude.| Nearest Land. | | Station. | | | | +----------+--------+-----------------------+---------------------------+ | | 1873. | | | | 1. |Feb. 15|27° 24' N., 16° 55' W.|S. of Tenerife. | | 2. | " 17|25° 52' N., 19° 22' W.|S.W. of the Canary Islands.| | 5. | " 21|24° 20' N., 24° 28' W.|S.W. of the Canary Islands.| | 9. | " 26|23° 23' N., 35° 11' W.| (Ocean). | | 24. |Mar. 25|18° 38' N., 65° 5' W.|Culebra (Antilles). | | | | | | | 32. |April 3|31° 49' N., 64° 55' W.|Bermuda. | | 45. |May 3|38° 34' N., 72° 10' W.|S. of New York. | | 50. | " 21|42° 8' N., 63° 39' W.|S. of Halifax. | | 64. |June 20|35° 35' N., 50° 27' W.| (Ocean). | | 76. |July 3|38° 11' N., 27° 9' W.|Azores. | | | | | | | 98. |Aug. 14| 9° 21' N., 18° 28' W.|W. of Sierra Leone. | | 106. | " 25| 1° 47' N., 24° 26' W.| (Ocean). | | 108. | " 27| 1° 10' N., 28° 23' W.| (Ocean). | | 111. | " 31| 1° 45' S., 30° 58' W.| (Ocean). | | 120. |Sept. 9| 8° 37' S., 34° 28' W.|Pernambuco. | | | | | | | 132. |Oct. 10|35° 25' S., 23° 40' W.|Tristan da Cunha. | | 134. | " 14|36° 12' S., 12° 16' W.|Tristan da Cunha. | | 137. | " 23|35° 59' S., 1° 34' E.| (Ocean). | | 138. | " 25|36° 22' S., 8° 12' E.| (Ocean). | | 143. |Dec. 19|36° 48' S., 19° 24' E.|Cape of Good Hope. | | | | | | | 144. | " 24|45° 57' S., 34° 39' E.| (Ocean). | | 145. | " 27|46° 43' S., 38° 4' E.|Prince Edward Island. | | 146. | " 29|46° 46' S., 45° 31' E.| (Ocean). | | 147. | " 30|46° 16' S., 48° 27' E.|W. of the Crozet Islands. | | | 1874. | | | | 148. |Jan. 3|46° 47' S., 51° 37' E.|E. of the Crozet Islands. | | | | | | | 149H. | " 29|48° 45' S., 69° 14' E.|Kerguelen Island. | | 150. |Feb. 2|52° 4' S., 71° 22' E.|N. of Heard Island. | | 151. | " 7|52° 59' S., 73° 33' E.|Heard Island. | | 152. | " 11|60° 52' S., 80° 20' E.|(Ocean). | | 153. | " 14|65° 42' S., 79° 49' E.|Antarctic Ice. | | | | | | | 154. | " 19|64° 37' S., 85° 49' E.|Antarctic Ice. | | 155. | " 23|64° 18' S., 94° 47' E.|Antarctic Ice. | | 156. | " 26|62° 26' S., 95° 44' E.| (Ocean). | | 157. |Mar. 3|53° 55' S., 108° 35' E.| (Ocean). | | 158. | " 7|50° 1' S., 123° 4' E.| (Ocean). | | | | | | | 159. | " 10|47° 25' S., 130° 22' E.| (Ocean). | | 160. | " 13|42° 42' S., 134° 10' E.| (Ocean). | | 162. |April 2|39° 10' S., 146° 37' E.|Bass Strait. | | 163. | " 4|36° 57' S., 150° 34' E.|Port Jackson. | | 164A. |June 13|34° 9' S., 151° 55' E.|W. of Sydney. | | | | | | | 165. | " 17|34° 50' S., 155° 28' E.| (Ocean). | | 166. | " 23|38° 50' S., 169° 20' E.|W. of New Zealand. | | 169. |July 10|37° 34' S., 179° 22' E.|E. of New Zealand. | | 175. |Aug. 12|19° 2' S., 177° 10' E.|Fiji Islands. | | 181. | " 25|13° 50' S., 151° 49' E.|Louisiades. | | | | | | | 193. |Sept. 28| 5° 24' S., 130° 37' E.|Banda Sea. | | 195. |Oct. 3| 4° 21' S., 129° 7' E.|Banda Sea. | | 197. | " 14| 0° 41' N., 126° 37' E.|E. of Celebes. | | 198. | " 20| 2° 55' N., 124° 58' E.|N. of Celebes. | | 200. | " 23| 6° 47' N., 122° 28' E.|W. of Mindanao. | | | | | | | 201. | " 26| 7° 3' N., 121° 48' E.|W. of Mindanao. | | 202. | " 27| 8° 32' N., 121° 55' E.|W. of Mindanao. | | 205. |Nov. 13|16° 42' N., 119° 22' E.|W. of Luzon. | | | 1875. | | | | 206. |Jan. 8|17° 54' N., 117° 14' E.|W. of Luzon. | | 211. | " 28| 8° 0' N., 121° 42' E.|W. of Mindanao. | | | | | | | 213. |Feb. 8| 5° 47' N., 124° 1' E.|S. of Mindanao. | | 214. | " 10| 4° 33' N., 127° 6' E.|N. of Gilolo. | | 215. | " 12| 4° 19' N., 130° 15' E.|N. of Gilolo. | | 216A. | " 16| 2° 56' N., 134° 11' E.|S. of Pelew Islands. | | 217. | " 22| 0° 39' S., 138° 55' E.|N. of New Guinea. | | | | | | | 218. |Mar. 1| 2° 33' S., 144° 4' E.|N. of New Guinea. | | 220. | " 11| 0° 42' S., 147° 0' E.|N. of New Guinea. | | 221. | " 13| 0° 40' N., 148° 41' E.| (Ocean). | | 222. | " 16| 2° 15' N., 146° 16' E.| (Ocean). | | 223. | " 19| 5° 31' N., 145° 13' E.|Carolines. | | | | | | | 224. | " 21| 7° 45' N., 144° 20' E.|Carolines. | | 225. | " 23|11° 24' N., 143° 16' E.|Ocean } | | 226. | " 25|14° 44' N., 142° 13' E.|Ocean } North-West Pacific,| | 230. |April 5|26° 29' N., 137° 57' E.|Ocean } between Carolines | | 231. | " 9|31° 8' N., 137° 8' E.|Ocean } and Japan. | | | | | } | | 232. |May 12|35° 11' N., 139° 28' E.|Ocean } | | 234. |June 3|32° 31' N., 135° 39' E.|S. of Japan. | | 235. | " 4|34° 7' N., 138° 0' E.|S. of Japan. | | 236. | " 5|34° 58' N., 139° 29' E.|S. of Japan. | | 237. | " 17|34° 37' N., 140° 32' E.|S. of Japan. | | | | | | | 238. | " 18|35° 18' N., 144° 8' E.|Ocean } | | 239. | " 19|35° 18' N., 147° 9' E.|Ocean } | | 240. | " 21|35° 20' N., 153° 39' E.|Ocean } | | 241. | " 23|35° 41' N., 157° 42' E.|Ocean } | | 242. | " 24|35° 29' N., 161° 52' E.|Ocean } | | | | | } | | 243. | " 26|35° 24' N., 166° 35' E.|Ocean } North Pacific, | | 244. | " 28|35° 22' N., 169° 53' E.|Ocean } between Japan and | | 245. | " 30|36° 23' N., 174° 31' E.|Ocean } San Francisco | | 246. |July 2|36° 10' N., 178° 0' E.|Ocean } (35°-38° N. lat., | | 247. | " 3|35° 49' N., 179° 57' W.|Ocean } 144°-156° W. long.)| | | | | } | | 248. | " 5|37° 41' N., 177° 4' W.|Ocean } | | 249. | " 7|37° 59' N., 171° 48' W.|Ocean } | | 250. | " 9|37° 49' N., 166° 47' W.|Ocean } | | 251. | " 10|37° 37' N., 163° 26' W.|Ocean } | | 252. | " 12|37° 52' N., 160° 17' W.|Ocean } | | | | | } | | 253. | " 14|38° 9' N., 156° 25' W.|Ocean | | 254. | " 17|35° 13' N., 154° 43' W.|Ocean } | | 255. | " 19|32° 28' N., 154° 33' W.|Ocean } North Pacific | | 256. | " 21|30° 22' N., 154° 56' W.|Ocean } (35°-23° N. lat., | | 257. | " 23|27° 33' N., 154° 55' W.|Ocean }154°-156° W. long.).| | | | | } | | 258. | " 24|26° 11' N., 155° 12' W.|Ocean } | | 259. | " 26|23° 3' N., 156° 6' W.|Ocean } | | 261. |Aug. 12|20° 18' N., 157° 14' W.|Sandwich Islands. | | 262. | " 20|19° 12' N., 154° 14' W.|Sandwich Islands. | | 263. | " 21|17° 33' N., 153° 36' W.|Ocean } | | | | | } | | 264. | " 23|14° 19' N., 152° 37' W.|Ocean } | | 265. | " 25|12° 42' N., 152° 1' W.|Ocean } | | 266. | " 26|11° 7' N., 152° 3' W.|Ocean } Tropical Central | | 267. | " 28| 9° 28' N., 150° 49' W.|Ocean } Pacific, between | | 268. | " 30| 7° 35' N., 149° 49' W.|Ocean } Sandwich and | | | | | } | | 269. |Sept. 2| 5° 54' N., 147° 2' W.|Ocean } Paumotu | | 270. | " 4| 2° 34' N., 149° 9' W.|Ocean } (17° N. lat. to | | 271. | " 6| 0° 33' S., 151° 34' W.|Ocean } 11° S. lat.). | | 272. | " 8| 3° 48' S., 152° 56' W.|Ocean } | | 273. | " 9| 5° 11' S., 152° 56' W.|Ocean } | | | | | } | | 274. | " 11| 7° 25' S., 152° 15' W.|Ocean } | | 275. | " 14|11° 20' S., 150° 30' W.|Ocean } | | 276. | " 16|13° 28' S., 149° 30' W.|Paumotu. | | 280. |Oct. 4|18° 40' S., 149° 52' W.|S. of Tahiti. | | 281. | " 6|22° 21' S., 150° 17' W.|Tubuai Islands. | | | | | | | 282. | " 7|23° 46' S., 149° 59' W.|Tubuai Islands. | | 283. | " 9|26° 9' S., 145° 17' W.|N. of Oparo Island. | | 284. | " 11|28° 22' S., 141° 22' W.|S. of Oparo Island. | | 285. | " 14|32° 36' S., 137° 43' W.|Ocean } | | 286. | " 16|33° 29' S., 133° 22' W.|Ocean } | | | | | | | 287. | " 10|36° 32' S., 132° 52' W.|Ocean } | | 288. | " 21|40° 3' S., 132° 58' W.|Ocean } | | 289. | " 23|39° 41' S., 131° 23' W.|Ocean } | | 290. | " 25|39° 16' S., 124° 7' W.|Ocean } Open South Pacific | | 291. | " 27|39° 13' S., 118° 49' W.|Ocean } Ocean, between New | | | | | } Zealand and | | 292. | " 29|38° 43' S., 112° 31' W.|Ocean } Valparaiso. | | 293. |Nov. 1|39° 4' S., 105° 5' W.|Ocean } | | 294. | " 3|39° 22' S., 98° 46' W.|Ocean } | | 295. | " 5|38° 7' S., 94° 4' W.|Ocean } | | 296. | " 9|38° 6' S., 88° 2' W.|Ocean } | | | | | } | | 297. | " 11|37° 29' S., 83° 7' W.|Ocean } | | 298. | " 17|34° 7' S., 73° 56' W.|W. of Valparaiso. | | 299. |Dec. 14|33° 31' S., 74° 43' W.|W. of Valparaiso. | | 300. | " 17|33° 42' S., 78° 18' W.|N. of Juan Fernandez. | | 302. | " 28|42° 43' S., 82° 11' W.| (Ocean). | | | | | | | 303. | " 30|45° 31' S., 78° 9' W.|W. of Patagonia. | | 304. | " 31|46° 53' S., 75° 12' W.|W. of Patagonia. | | | 1876. | | | | 318. |Feb. 11|42° 32' S., 56° 29' W.| (Ocean). | | 319. | " 12|41° 54' S., 54° 48' W.| (Ocean). | | 323. | " 28|35° 39' S., 50° 47' W.|W. of Buenos Ayres. | | | | | } | | 324. | " 29|36° 9' S., 48° 22' W.|Ocean } | | 325. |Mar. 2|36° 44' S., 46° 16' W.|Ocean } | | 326. | " 3|37° 3' S., 44° 17' W.|Ocean } Open South Atlantic| | 327. | " 4|36° 48' S., 42° 45' W.|Ocean } Ocean, between | | 328. | " 6|37° 38' S., 39° 36' W.|Ocean } Buenos Ayres and | | | | | } | | 329. | " 7|37° 31' S., 36° 7' W.|Ocean } Tristan da Cunha | | 330. | " 8|37° 45' S., 33° 0' W.|Ocean } (35°-37° S. lat., | | 331. | " 9|37° 47' S., 30° 20' W.|Ocean } 21°-48° W. long.). | | 332. | " 10|37° 29' S., 27° 31' W.|Ocean } | | 333. | " 13|35° 36' S., 21° 12' W.|Ocean } | | | | | | | 334. | " 14|35° 45' S., 18° 31' W.|W. of Tristan da Cunha. | | 335. | " 16|32° 24' S., 13° 5' W.|N. of Tristan da Cunha. | | 338. | " 21|21° 15' S., 14° 2' W.|(Ocean). | | 340. | " 24|14° 33' S., 13° 42' W.|Ocean } | | 341. | " 25|12° 16' S., 13° 44' W.|Ocean } W. of St. Helena. | | | | | | | 342. | " 26| 9° 43' S., 13° 51' W.|Ocean } | | 343. | " 27| 8° 3' S., 14° 27' W.|Ascension Island. | | 344. |April 3| 7° 54' S., 14° 28' W.|Ascension Island. | | 345. | " 4| 5° 45' S., 14° 25' W.|Ocean } | | 346. | " 6| 2° 42' S., 14° 41' W.|Ocean } Tropical Atlantic, | | | | | } between Ascension | | 347. | " 7| 0° 15' S., 14° 25' W.|Ocean } and Sierra Leone. | | 348. | " 9| 3° 10' N., 14° 51' W.|Ocean } | | 349. | " 10| 5° 28' N., 14° 38' W.|Ocean } | | 350. | " 11| 7° 33' N., 15° 16' W.|W. of Sierra Leone. | | 351. | " 12| 9° 9' N., 16° 41' W.|W. of Sierra Leone. | | | | | | | 352. | " 13|10° 55' N., 17° 46' W.|W. of Sierra Leone. | | 353. |May 3|26° 21' N., 33° 37' W.|W. of Canary Islands. | | 354. | " 6|32° 41' N., 36° 6' W.|S. of Azores. | +----------+--------+-----------------------+---------------------------+

{clxiv}CHAPTER X.--GEOGRAPHICAL DISTRIBUTION.

(§§ 241-250.)

241. Historical Distribution.--Radiolaria are found fossil in all the more important groups of the sedimentary rocks of the earth's crust. Whilst a few years ago their well-preserved siliceous skeletons were only known in considerable quantity from Cainozoic marls (§ 242), very many SPUMELLARIA and NASSELLARIA have recently been found in Mesozoic and a few in Palæozoic strata. By the aid of improved modern methods of investigation (especially by the preparation of thin sections of very hard rocks) it has been shown that many hard siliceous minerals, especially cryptocrystalline quartz, contain numerous well-preserved Radiolaria, and sometimes are mainly composed of closely compacted masses of such siliceous shells; of this kind are many quartzites of the Jura (§ 243). These Jurassic quartzes (Switzerland), as well as the Tertiary marls (Barbados) and clays (Nicobar Islands), are to be regarded as "fossil Radiolarian ooze" (§ 237). Dense masses of compressed SPUMELLARIA and NASSELLARIA form the principal part of these rocks. Isolated or in smaller quantities, fossil Polycystina, belonging to different families of SPUMELLARIA and NASSELLARIA, also occur in in other rocks, and even in some of Palæozoic origin. Since specimens have also been recently found both in Silurian and Cambrian strata, it may be stated that as regards their historical distribution, Radiolaria occur in all fossiliferous sedimentary deposits, from the oldest to those of the present time.

242. Cainozoic Radiolaria.--The great majority of fossil Radiolaria which have hitherto been described, belong to the Cainozoic or Tertiary period, and in fact, to its middle portion, the Miocene period. At this period the richest and most important of all the Radiolarian formations were deposited, such as the pure "Polycystine marl" of Barbados (see note A), also that of Grotte in Sicily (see note B), and the clay of the Nicobar Islands (see note C). Besides the above-mentioned deposits, which may be designated "pure" fossil Radiolarian ooze, many deposits containing these organisms have recently been discovered in widely separated parts of the earth, partly of the nature of tripoli or marl, partly resembling clay. Among these may be mentioned in the first place many coasts and islands of the Mediterranean, both on the south coast of Europe (Sicily, Calabria, Greece), and the north coast of Africa (from Oran to Tripoli). The extensive layers of tripoli which are found in these Mediterranean Tertiary mountains belong to the upper Miocene (Tortona stage), and consist partly of marl rich in calcareous matter, and resembling chalk, partly passing over into plastic clay or "Kieselguhr" (§ 246). The quantity of Radiolaria contained varies, and is more conspicuous the fewer the calcareous shells of Foraminifera present. Similar Tertiary Polycystine formations occur in some parts of America (see note D); probably they have a very wide distribution. In their general morphological characters, the Tertiary SPUMELLARIA and NASSELLARIA {clxv}are related to those forms which are found in the recent Radiolarian ooze of the depths of the Pacific, especially to the species which are characteristic of the Challenger Stations 225, 226, 265 and 268. Many living genera and families (e.g., most #Larcoidea# and #Stephoidea#) have not yet been found in the Tertiary formations.

A. The famous Polycystine marl of Barbados in the Antilles, which Robert Schomburgk discovered forty years ago, belongs to the Miocene formation, and is the richest and best known of all the important Radiolarian deposits (see L. N. 16, pp. 5-8). After Ehrenberg had published in December 1846 the first preliminary communication regarding its composition out of masses of well-preserved Polycystina, he was able in the following year to describe no less than 282 species from it; he distributed these in 44 genera and 7 families (L. N. 4, 1847, p. 54). In the year 1854 Ehrenberg published figures of 33 species in his Mikrogeologie (L. N. 6, Taf. xxxvi.); but it was only in 1873 that he published descriptions of 265 species (Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, Jan. 30, pp. 213-263). Finally there followed in 1875 his Fortsetzung der Mikrogeologischen Studien, mit specieller Rücksicht auf den Polycystinen-Mergel von Barbados (L. N. 25). On the thirty plates which accompany this the last work of Ehrenberg, 282 species are figured and named, of which 54 are SPUMELLARIA (13 #Sphæroidea#, 8 #Prunoidea#, 33 #Discoidea#), and 228 NASSELLARIA (2 #Stephoidea#, 38 #Spyroidea#, and 188 #Cyrtoidea#). The fourth section of this memoir contains a survey of the Polycystine formation of Barbados (pp. 106-115), and the fifth section the special description of a large specimen of rock from Mount Hillaby in Barbados (see also L. N. 28, p. 117, and L. N. 41, pp. 476-478). The account given by Ehrenberg of the Polycystina of Barbados is in many respects very incomplete, and very far from exhausting this rich mine of remarkable forms. This may be readily seen from the twenty-five plates of figures of Polycystins in the Barbados Chalk Deposit published by Bury in 1862 (L. N. 17). The number of species here figured (140 to 142) is about half of those given by Ehrenberg; and there are among them numerous generic types, some of great interest, which were entirely overlooked by the latter; e.g. Saturnalis (#Sphæroidea#), Cannartidium (#Prunoidea#), Tympanidium (#Stephoidea#), Cinclopyramis (#Cyrtoidea#), &c. Finally, Ehrenberg always (until 1875) ignored Bury's atlas, which had been published thirteen years ago and was quite accessible to him. How different were the contents of the two works may easily be seen from the following abstract.

Comparative View of the Species of Fossil Radiolaria from Barbados made known by the figures of Bury in 1862 and of Ehrenberg in 1875.

+-------------------+--------------------+--------+-----------+-------+ | Legion. | Order. | Bury. | Ehrenberg.| Total.| +-------------------+--------------------+--------+-----------+-------+ | I. Legion | { 1. Sphæroidea | 16 | 13 | 29 | | SPUMELLARIA | { 2. Prunoidea | 10 | 8 | 18 | | (PERIPYLEA). | { 3. Discoidea | 37 | 33 | 70 | | | | | | | | II. Legion | { 4. Stephoidea | 5 | 2 | 7 | | NASSELLARIA | { 5. Spyroidea | 13 | 38 | 51 | | (MONOPYLEA). | { 6. Cyrtoidea | 60 | 188 | 248 | +-------------------+--------------------+--------+-----------+-------+ | Total, | 141 | 282 | 423 | +----------------------------------------+--------+-----------+-------+

{clxvi}In 1882 Bütschli still further increased the number of known Radiolaria from Barbados both by figures and descriptions (L. N. 40), and gave in particular a very accurate morphological analysis of 12 new NASSELLARIA (3 #Stephoidea#, 3 #Spyroidea#, and 6 #Cyrtoidea#; L. N. 40, Taf. xxxii., xxxiii.). The number of the fossil species collected in the Barbados marl is, however, greater than would appear from the above-quoted communications. My respected friend, Dr. R. Teuscher, of Jena, has, at my request, made a large number (about a thousand) of very accurate drawings with the camera lucida of Polycystina from Barbados (see p. 1760). From these it appears that the variations in the structure of the shells, with respect to number, size, and form of the lattice-pores, of the spines, &c., is much greater than would be supposed from the figures of Ehrenberg and Bury. I have thus come to the conviction that the number of species from Barbados (using the word "species" in the sense understood by those authors) is not less than 400 and probably more than 500. Descriptions of some particularly interesting new species from this series have been included in the systematic account of the Challenger Radiolaria. A complete critical investigation of the Radiolaria of Barbados, and especially an accurate comparison of these Cainozoic species with the Mesozoic forms from the Jura, on the one hand, and with recent types on the other, must be left to the future for its accomplishment (see § 246).

B. The Cainozoic Polycystine tripoli or marl of the Mediterranean coast, which is probably always of Miocene origin, forms very extensive mountain ranges both in the south of Europe (Sicily, Calabria, Greece) and in the north of Africa (from Oran to Tripoli) (§ 246). Hitherto, however, only one locality has been thoroughly investigated, namely, Grotte in the province of Girgenti in Sicily (L. N. 35). In the accurate account which was given of it by Stöhr in 1880, 118 species were described, distributed in 40 genera (L. N. 35; pp. 72-84); of these 118 species 78 are quite new, 25 are identical with previously known fossils, and 29 identical with living forms. Among them are 73 SPUMELLARIA (28 #Sphæroidea#, 8 #Prunoidea#, and 37 #Discoidea#), but only 40 NASSELLARIA (1 #Stephoidea#, 6 #Spyroidea#, and 33 #Cyrtoidea#), and 5 PHÆODARIA (Dictyochida). The other parts of Sicily from which the same upper Miocene tripoli has been investigated (belonging to the Tortona stage) have proved less rich than Grotte. The best known of these places is Caltanisetta, since upon three genera discovered here (Haliomma, Cornutella, Lithocampe) the group Polycystina was founded by Ehrenberg in 1838 (see L. N. 16, p. 3). Afterwards 31 species were described from this locality, of which 23 were again found in Grotte. The richest deposit on the Mediterranean coast, however, appears to be at Oran. A small specimen of the Kieselguhr found there, which was recently sent to me by Professor Steinman, proved to be pure Radiolarian ooze, very similar to that now found in the Central Pacific, and contained many hitherto undescribed species; it is deserving of careful investigation and comparison.

C. Regarding the Tertiary Radiolarian clay of the Nicobar Islands, see § 247 and L. N. 25, pp. 116-120. Its fauna is incompletely known; probably it is of Miocene or Oligocene origin.

D. Cainozoic tripoli, containing larger or smaller quantities of Radiolaria, appears to be rather widely distributed in America. Ehrenberg has described such from South America (polishing-slate from Morro di Mijellones, on the coast between Chili and Bolivia), and from North America (Richmond and Petersburg in Virginia, Piscataway in Maryland). Similar deposits are also found in the Bermuda Islands (L. N. 4, 1855-56; L. N. 6, Taf. 18; L. N. 16, pp. 3-9; L. N. 41, pp. 475-478, and L. N. 25, pp. 2-6).

{clxvii}243. Mesozoic Radiolaria.--From the Mesozoic or Secondary period numerous well-preserved Radiolaria have recently been described. They belong for the most part to the Jurassic formation (see notes A, B, C), whilst the more recent Chalk (see note D) and the older Trias (see note E) have hitherto yielded but few species. All the main divisions of the Jura, both the upper (Malm) and the middle (Dogger), and especially the lower (Lias) appear in certain localities to be very rich in well-preserved shells of fossil Polycystina. Most of these are aggregated together in coprolites and quartzites (jasper, chert, flint, &c., § 248). The majority are #Cyrtoidea#, the minority #Sphæroidea# and #Discoidea# in almost equal proportions; a few #Beloidea# (Sphærozoum) and #Phæocystina# (Dictyocha) are also found among them. The general morphological character of these Jurassic Radiolaria is very different from that of the nearly related Tertiary and living forms. In general, their siliceous shells are firmer and more massive, usually also somewhat larger, but of simpler structure. The manifold delicate appendages (spines, bristles, feet, wings, &c.) which are so richly developed in the living SPUMELLARIA and NASSELLARIA, and are also well shown in the Tertiary species, are entirely wanting in the majority of the Jurassic Polycystina. The #Sphæroidea# and #Prunoidea# are all simple spherical or ellipsoidal lattice-shells (Monosphærida); concentric lattice-shells (Polysphærida) are entirely wanting. The #Cyrtoidea# are, for the most part, devoid of radial processes or basal feet (Eradiata); triradiate and multiradiate forms, such as are found abundantly in the recent and Tertiary formations, are very rare. The large number of many-jointed forms (Stichocyrtida) and of #Cyrtoidea# with latticed basal opening is very striking.

A. The most important work on the Jurassic Radiolaria, regarding which but little was known prior to the year 1885, is the valuable and in some respects very interesting Beiträge zur Kenntniss der fossilen Radiolarien aus Gesteinen des Jura, by Dr. Rüst of Freiburg i. B. (1885, Palæontographica, Bd. xxxi. 51 pp. with 12 plates). Unfortunately this important work was issued only when about half of the present Report was printed off, so that it was no longer possible to include the 234 species there described in its systematic part. I have therefore elsewhere given a list of the Jurassic Radiolaria, and at present only make the following remarks:--Of the 234 species described, the larger half (130) belong to the NASSELLARIA (#Cyrtoidea#), the smaller half (102) to the SPUMELLARIA (38 #Sphæroidea#, 14 #Prunoidea#, and 50 #Discoidea#). In addition, there are 2 PHÆODARIA depicted, and several spicules which are probably to be referred to the #Beloidea#. Among the 130 #Cyrtoidea# (of which 2 are described as #Botryodea#), there are 24 Monocyrtida, 14 Dicyrtida, 22 Tricyrtida, and 70 Stichocyrtida. Just as striking as the predominant number of the last is the fact that there are only very few triradiate (9) and multiradiate (4) species found among these 130 #Cyrtoidea#, as also the large number of species with latticed basal opening; #Stephoidea# appear to be entirely wanting. The rich material of jasper, chert, flint, and coprolites in which Dr. Rüst found these Radiolaria, is derived for the most part from the Jurassic rocks of Germany (Hanover, South Bavaria), Tyrol, and Switzerland (compare § 248).

{clxviii}B. Jurassic Radiolaria from Italy, also found in jasper, which are closely related to the forms from Germany and Switzerland described by Dr. Rüst, were made known so long ago as 1880 by Dante Pantanelli in his treatise I Diaspri della Toscana e i loro Fossili (Rome, 1880, 33 pp. 60 figs.). Pantanelli believes, however, that this jasper is for the most part of Eocene origin; but from his description, and especially from the morphological character of the forms which he figures, it appears very probable "that these Tuscan jaspers from Galestro, like those of the Swiss conglomerates, are found in a secondary locality and belong to the Jurassic period" (Rüst, L. N. 51, p. 3). Unfortunately the figures of Pantanelli are so small and incomplete that a reliable determination of the species is hardly possible; for example, the lattice-work is only given in ten of the sixty figures. Among the 32 recorded species 15 are SPUMELLARIA (6 #Sphæroidea# and 9 #Discoidea#) and 17 NASSELLARIA (4 #Stephoidea# and 13 #Cyrtoidea#); many of which seem to be identical with the forms more accurately described by Dr. Rüst (compare p. 1762).

C. From the Lias of the Alps and more particularly "from the lower Liassic beds of the Schafberg near Salzburg," Dr. Emil von Dunikowski in 1882 described 18 species of fossil Radiolaria (L. N. 44, pp. 22-34, Taf. iv.-vi.); most of these are #Sphæroidea# and #Discoidea# and appear to have been more or less altered by petrological changes; their spongy structure is probably secondary.

D. Cretaceous Radiolaria have been hitherto described only in very small numbers; quite recently Dr. Rüst has found a larger number chiefly in flints from the English chalk, but they have not yet been published. In 1876 Zittel described 6 very well-preserved species from the upper chalk of North Germany (L. N. 29, pp. 76-96, Taf. ii.); among them were 1 #Sphæroidea#, 1 #Discoidea#, 1 Dictyocha, and 3 #Cyrtoidea#.

E. Triassic Radiolaria have recently been discovered by Dr. Rüst in chert, but have not yet been described.

244. Palæozoic Radiolaria.--The number of Radiolaria which are known from the Palæozoic or Primary formations is much less than from either the Mesozoic or Cainozoic periods. Here, however, the investigations of recent times have yielded important information; a few species, at all events, of Polycystina (mostly #Sphæroidea#) are now known from various Palæozoic formations, and not only from the Permian ("Zechstein") and the Coal-measures, but also from the older Devonian and Silurian systems. Even in the still older Cambrian rocks a few fossil Radiolaria have been found. All these Palæozoic Radiolaria are Polycystina of very simple form and primitive structure, mostly simple SPUMELLARIA (latticed spheres, ellipsoids, lenses, &c.), but partly also simple NASSELLARIA.

The important discoveries which have recently been made by Dr. Rüst regarding the occurrence of Radiolaria in all the Palæozoic formations have not yet been published. From conversations with this estimable palæontologist I have learned, however, that he has pursued his fruitful investigation of the Mesozoic quartzites (§ 243), and has met with no less success in the case of similar Palæozoic structures. Although the number of species hitherto discovered is relatively small, the important conclusion appears to be warranted that they extend as far as the Silurian and Cambrian systems. All these very ancient SPUMELLARIA (#Sphæroidea#) and NASSELLARIA (#Cyrtoidea#) {clxix}exhibit very primitive structural relations. The occurrence of fossil Polycystina in the Carboniferous formation of England has been incidentally mentioned by W. J. Sollas:--"In the carboniferous beds of North Wales pseudomorphs of Radiolaria in calcite occur, along with minute quartz crystals" (Ann. and Mag. Nat. Hist., 1880, ser. 5, vol. vi. p. 439); and in the siliceous slate-beds of Saxony Rothpletz has shown the existence of a few #Sphæroidea# (Zeitschr. d. Deutsch. Geol. Gesellsch., 1800, p. 447).

245. Abundance of Radiolaria in the Various Rocks.--The relative quantity of well-preserved or at all events recognisable Radiolaria in the different rocks is very variable. In this respect three different degrees may be distinguished, which may be called shortly "pure, mixed, and poor" Radiolarian formations. The pure Radiolarian rocks consist for the greater part (usually much more than half, sometimes even more than three-quarters) of closely compacted often calcined masses of siliceous Polycystine shells. To this category belong the pure Miocene Polycystine marls of Barbados (§ 246), the Tertiary Polycystine clay of the Nicobar Islands (§ 247), and the Polycystine quartz of the Jura (§ 248). All these pure Radiolarian rocks may be regarded as fossil Radiolarian ooze (§ 237), and are certainly of deep-sea origin, having probably been deposited at depths greater than 2000 fathoms. Their palæontological character also is in favour of this view, for the abyssal Osculosa (§ 235) are more abundant and richer in species than the pelagic Porulosa (§ 233). The elevation of this deep-sea layer above the surface of the sea appears to have taken place but seldom; it has only been observed on a large scale at Barbados and in the Nicobar Islands. The mixed Radiolarian rocks are much more common; they were probably deposited at much less depths, or perhaps are not true deep-sea formations at all. The siliceous shells of Polycystina always constitute less than half (sometimes less than one-tenth) of their mass, and are less prominent than other siliceous remains (Diatoms), or calcareous remains (Foraminifera), or in some cases than the mineral constituents (pumice, &c.). To this group belong many of the above-mentioned Tertiary marls and clays (especially the Mediterranean Tripoli), also many flints, cherts, and other quartzites from Mesozoic strata (especially from the Jura), and probably also some palæozoic quartzites. The marine ooze from which they have originated may have been deposited at very various, even at slight, depths of the ocean. Formations poor in Radiolaria, which contain only a few species of SPUMELLARIA and NASSELLARIA mingled with other fossil remains and mineral particles, occur in all formations and are probably very widely distributed. Further careful examination of thin sections (especially of coprolites) will yield here a rich harvest of new forms. Both the mixed and the pure Radiolarian formations may be divided according to their petrographic characters into three groups, which, however, are connected by intermediate varieties--(1) soft, chalky marl (§ 246), (2) plastic clay (§ 247), and (3) hard, flinty quartz (§ 248).

{clxx}246. Radiolarian Marl.--Those soft, friable rocks, which contain a large quantity of calcareous matter, but consist for the most part of the shells of SPUMELLARIA and NASSELLARIA, are called Radiolarian or Polycystine marl, often more correctly Polycystine tripoli; the best known example of them is the chalky marl of Barbados in the Antilles (§ 242). The Tertiary mountain system of this island, which in Mount Hillaby rises to a height of 1147 feet and includes about 15,800 acres, consists almost exclusively of these remarkable masses of rock. Most of it appears as a soft, earthy, often chalky marl, with a considerable but variable amount of calcareous matter. Those specimens, the greater half of which is composed of well-preserved siliceous shells of Polycystina, and which contain little lime, approach the tripoli and "Kieselguhr." Those specimens, however, which contain the largest amount of calcareous matter resemble common writing chalk in consistency, and consist for the most part of shells of Foraminifera and their fragments; of these there are only few species but large numbers of individuals, generally in small fragments with a fine calcareous powder between them. They may be regarded as fossil Globigerina ooze (§ 238). In a third group of specimens from Barbados the quantity of fragments of pumice and other volcanic matters predominates; the amount of clay is also very considerable; these deposits pass over partly into actual clay partly into volcanic tuff. A fourth group exhibits relations to a coarser often ferruginous material, and although the shells of Polycystina are less abundant in it, still it may be shown to be composed largely of fragments and metamorphosed remains of them. The colour of this deposit, which in some places passes over into sandstone, in others into clay, is usually rather dark, grey, brown, sometimes red and occasionally black (bituminous). The Radiolarian marls of the first two groups, which sometimes approach the white chalk, sometimes the Kieselguhr, are grey, or even pure white (see note A). The same constitution is exhibited by the yellowish or white, very light and friable Polycystine marls of Sicily, which in Caltanisetta approach the chalk, and in Grotte the Kieselguhr. In Greece (Ægina, Zante, &c.), on the other hand, they pass over into plastic clay, and the same occurs in the Baden marl of the Vienna basin. In North Africa, however, on the Mediterranean shores of which the Radiolarian marl seems to be very widely distributed (from Tripoli to Oran), it sometimes becomes changed into actual firm polishing slate, sometimes into pulverulent Kieselguhr or tripoli (Terra tripolitana, see note B). Most of these Radiolarian marls appear to date from the middle Tertiary (Miocene) period, and to be deep-sea formations.

A. The Polycystine marl of Barbados appears at different parts of the island to present greater variations in its petrographical and zoographical composition than would appear from Ehrenberg's description (1875, L. N. 25, pp. 106-116). Through the kindness of one of my former students, Dr. Dorner, to whom I take this opportunity of expressing my thanks for the favour, I received a large number of specimens of Barbados rock, taken from various parts of the island, and they exhibit very great variations in their external appearance, their chemical composition, and the {clxxi}Radiolaria which they contain. The white specimens resembling Kieselguhr contained approximately 60 to 70 per cent. by volume of Radiolarian shells, the yellowish marl 40 to 50 per cent., and the brown and black (bituminous) marl 10 to 20 per cent. or less. Two analyses of the first, which my friend Dr. W. Weber was good enough to carry out, yielded different results from those which are given by Ehrenberg on the basis of Rammelsberg's analyses (L. N. 25, p. 116). The results of both are here given for comparison.

--------------------------------+--------------------------+------------- Ehrenberg-Rammelsberg | Weber I. | Weber II. (Fragment from Hillaby). | (Chalk-like Fragment). |(Tripoli-like | | Fragment). --------------------------------+--------------------------+------------- Silicate of alumina, 59.47 |Silica, 52.2 | 71.3 Alumina and oxide of iron, 1.95 |Alumina (with traces | Calcium carbonate, 34.31 | of oxide of iron), 12.3 | 11.2 Water, 3.67 |Lime and magnesia, 31.9 | 14.8 |Carbon dioxide, 3.2 | 2.7 ______ | _____ | _____ Total, 99.40 | Total, 99.6 | 100.0 --------------------------------+--------------------------+-------------

For further comparison I here add the three different analyses of Miocene Tripoli-marls from Sicily, given by Stöhr on the authority of Fremy, Schwager, and Mottura (Tagebl. d. fünfzigsten Versamml. Deutsch. Naturf. u. Aertzte in München, 1877, p. 163).

--------------------------+-------------+--------------+------------- Composition. |Tripoli from | Tripoli from | Tripoli from | Licata | Grotte | Caltanisetta | (Fremy). | (Schwager). | (Mottura). --------------------------+-------------+--------------+------------- Silica, | 30.98 | 58.58 | 68.6 Alumina, | 17.54 | 11.51 | } Oxide of iron, | 0.33 | 1.84 | } 3.6 | | | Lime, } | 38.09 | { 8.49 | } Magnesia, } | | { 0.41 | } 12.1 | | | Water and organic matter,}| | { 11.26 | } Carbonic acid, }| 13.06 | { 7.12 | } 15.2 +-------------+--------------+------------ | 100.00 | 99.21 | 99.5 --------------------------+-------------+--------------+-------------

B. The Radiolarian marl of the Mediterranean appears, judging by the accounts already published, to stretch along a considerable part of the coast in the earlier and middle Tertiary formations; thus it occurs of similar composition in widely separated localities, in Sicily, Calabria, Zante, and Greece; in North Africa from Tripoli to Oran and probably much farther. So long ago as 1854 Ehrenberg, in his Mikrogeologie (L. N. 6) gave a series of important, even if incomplete, communications regarding the "chalky white calcareous marl of Caltanisetta" (Taf. xxii.), the "Platten marl of Zante" (Taf. xx.), the "plastic clay of Ægina" (Taf xix.), and the "polishing slate of Oran" (Taf. xxi.). In 1880 Stöhr showed in his fundamental description of the Tripoli from {clxxii}Grotte in Sicily (L. N. 35) that its Radiolarian fauna is much richer than Ehrenberg supposed. The same is the case in the Tripoli of Caltanisetta, and also in the Baden marl of the Vienna basin. The richest deposit appears to be the pure Kieselguhr-like Tripoli from Oran; a small specimen, which was recently sent to me by Professor Steinmann of Freiburg, i. B., contained many hitherto undescribed species, and was at least as rich as the purest Barbados marl.

247. Radiolarian Clays.--Among the Radiolarian or Polycystine clays we include the firm, often plastic, formations, which contain a larger proportion of Radiolaria than of other organic remains. The first of these to be mentioned is the Cainozoic formation of the Nicobar Islands in Further India, which rises to a height of 2000 feet above the level of the sea, and consists for the most part of coloured masses of clay of varying constitution; on Car Nicobar these are mostly grey or reddish, on the Island of Camorta they are partly strongly ferruginous and red and yellow (e.g. at Frederickshaven), partly white and light, like meerschaum (e.g. at Mongkata). The latter varieties appear to pass over into pure loose Polycystine marl like that of Barbados, the former into calcareous sandstone. Although the Polycystine clays of the Nicobar Islands are as yet only very incompletely known, it may be concluded with great probability that they are true deep-sea formations and nearly allied to those recent forms of red clay, which by their abundance in Radiolaria most nearly approach the Radiolarian ooze, such for example as the red clay of the North Pacific between Japan and the Sandwich Islands (Stations 241 to 245, compare §§ 229 and 239). With this view agrees also the greater or less quantity of pumice dust and other volcanic products. Probably Radiolarian clays like those of the Nicobar Islands occur also in other Tertiary rocks; part of the Barbados marl passes by gradually increasing content of clay into such; and in this case also the amount of included pumice is often considerable. Many mixed Radiolarian marls of the Mediterranean (e.g., of Greece and Oran) also appear to pass over at certain points into Radiolarian clay.

The Radiolarian clays of the Nicobar Islands are unfortunately very incompletely known both as regards their geological nature and their palæontological composition. The communications of Rink (Die Nikobaren-Inseln, eine geographische Skizze, Kopenhagen, 1847) and of Ehrenberg (L. N. 6, p. 160 and L. N. 25, pp. 116 to 120) leave many important questions unanswered. The latter has only figured twenty-three species in his Mikrogeologie (L. N. 6, Taf. xxxvi.). In his tabular list of names (L. N. 25, p. 120) he only incompletely records thirty-nine species, although in 1850, immediately after the first examination of the Nicobar clay, he had distinguished "more than a hundred species, partly new, partly identical with those of Barbados" (L. N. 16, p. 8). I have unfortunately been unable in spite of many efforts, to obtain for investigation a specimen of Nicobar clay. The only microscopical preparation (from Ehrenberg's collection), which I was able to examine, contained several hitherto undescribed species. A thorough systematic examination of these important Radiolarian clays is a pressing necessity, especially as they seem to be markedly different from those of the Mediterranean (from Ægina, Zante, &c.).

{clxxiii}248. Radiolarian Quartzes.--Under the name Radiolarian or Polycystine quartzes are included those hard, siliceous rocks, which consist for the most part of the closely compacted shells of SPUMELLARIA and NASSELLARIA. To these "cryptocrystalline quartzes," or better, quartzites, belong more especially the pure Radiolarian formations of the Jura, which have been described as flint, chert, jasper, as well as other cryptocrystalline quartzites. Most of the rocks of this nature hitherto examined are from Germany (Hanover, South Bavaria), Hungary, Tyrol, and Switzerland; others are known from Italy (Tuscany). They occur both in the upper and middle, but especially in the lower Jurassic formation (also in the lower layers of the Alpine Lias). A small part of them has been examined in their primary situation (the red jaspers of Allgäu and Tyrol), the greater part, however, only as loose rolled stones in secondary situations (thus in Switzerland in the breccia of the Rigi, in the conglomerate of the Uetli-Berg, and in many boulders of the Rhine, the Limmat, the Reuss, and the Aar). The greatest abundance, however, of Jurassic Radiolaria has been yielded by the silicified coprolites from the Lias of Hanover. These "Radiolarian coprolites" are roundish or cylindrical bodies, which may attain the size of a goose-egg; they probably originated from Fish or Cephalopods, which had fed upon Crustacea, Pteropoda, and similar pelagic organisms, whose stomachs were already full of Radiolarian skeletons. Next to the coprolites the richest is the red jasper, whose colour varies from bright to dark red; it constitutes a true "silicified deep-sea Radiolarian ooze." The "Aptychus beds" also of South Bavaria and Tyrol are very rich, and have furnished about one-third of all the Radiolaria known from the Jura; most of the species too are very well preserved (compare § 243).

Regarding the remarkable composition and manifold varieties of the Jurassic Radiolarian quartz, the very full treatise of Dr. Rüst may be consulted (L. N. 51). The very interesting Radiolarian coprolites, which that author has discovered in the lower and middle Jura of Hanover, occur in astonishing numbers in the iron mines at the village of Gross-Ilsede, four and a half miles south of the town of Peine. They constitute from 2 to 5 per cent. by weight of the Liassic iron ore; of this latter, in the year 1883 alone, not less than two hundred and eighty million kilograms were excavated. It is very probable that the careful microscopic examination of thin sections of coprolites, as well as of flints, chert, jasper, and other quartzites, would yield a rich harvest of fossil Radiolaria in other formations also. In Italy Dante Pantanelli has discovered interesting Polycystine jaspers in Tuscany (L. N. 36, 45); these also appear to occur in the Jura (compare § 243, and L. N. 51, pp. 3-10).

249. Fossil Groups.--The preservation of Radiolaria in the fossil state is, of course, primarily dependent on the composition of their skeleton. Hence the ACANTHARIA, whose acanthin skeleton although firm is readily soluble, are never found fossil. The same is true of the skeletons of the PHÆODARIA, which consist of a silicate of carbon; here, however, a single exception is found in the Dictyochida, a subfamily of the Cannorrhaphida, the isolated parts of whose skeletons appear to consist of pure silica, and {clxxiv}are often found fossil. Of the two other legions those families which possess no skeleton are of course excluded; the Nassellida among the NASSELLARIA, and the Thalassicollida and Collozoida among the SPUMELLARIA. Thus of the 85 known families there remain scarcely 55 of which the skeletons may be expected in the fossil state; and of these scarcely half have been actually observed in this condition. Of the 20 orders of this class enumerated in § 155, the following 9 may be, for palæontological and geological purposes, completely excluded:--(A) The 4 orders of ACANTHARIA (1, #Actinelida#; 2, #Acanthonida#; 3, #Sphærophracta#; 4, #Prunophracta#); (B) 3 orders of PHÆODARIA (5, #Phæosphæria#; 6, #Phæogromia#; 7, #Phæoconchia#); (C) 1 order of NASSELLARIA (8, #Nassoidea#); (D) 1 order of SPUMELLARIA (9, #Colloidea#). From a geological point of view the following 6 orders, although occasionally found fossil, are of quite subordinate importance:--(A) Among the SPUMELLARIA (10, #Beloidea#, and 11, #Larcoidea#); (B) among the NASSELLARIA (12, #Plectoidea#; 13, #Stephoidea#; 14, #Botryodea#); (C) among the PHÆODARIA (15, the #Phæocystina#). On the other hand the following 5 orders, which are the main constituents of Radiolarian rocks, are of pre-eminent geological importance:--(A) Among the SPUMELLARIA (16, #Sphæroidea#; 17, #Prunoidea#; 18, #Discoidea#); (B) among the NASSELLARIA (19, #Spyroidea#, and 20, #Cyrtoidea#). The numerical relation in which the different families of these orders appear in the Radiolarian formations may be seen on consulting § 157.

250. Fossil and Recent Species.--The fact that there are many Radiolaria living at the present day, whose shells are found fossil in Tertiary rocks, is of great phylogenetic and geological significance. This appeared to be the case even from the older observations upon the Polycystina of the Barbados marl (see note A), but more recent and extensive observations both upon these and upon the Miocene Radiolaria of Sicily, have shown that the number of these "living fossil" forms is much greater than was previously supposed (see note B). Among the Miocene Radiolaria numerous species, both of SPUMELLARIA (especially #Sphæroidea# and #Discoidea#) and of NASSELLARIA (especially #Spyroidea# and #Cyrtoidea#) are not to be distinguished from the corresponding still living forms (see notes C, D). On the other hand, those genera, which are rich both in species and individuals (recent as well as fossil), present continuous series of forms which lead gradually and uninterruptedly from old Tertiary species to others still living, which are specifically indistinguishable from them. These interesting morphological facts are capable of direct phylogenetic application, and furnish valuable proofs of the truth of the theory of descent.

A. Ehrenberg, in his list of fossil Polycystina (L. N. 25, pp. 64-85, 1875), records 325 species of which 26 are still living.

{clxxv}B. Stöhr, in his list of Miocene Radiolaria from Grotte (L. N. 35, p. 84, 1880), records 118 species, of which 29 are still living.

C. Teuscher, who at my request has made a large number of comparative measurements and drawings, both of fossil and living Radiolaria, comes to the conclusion that numerous SPUMELLARIA and NASSELLARIA from Barbados are to-day extant and unchanged in the Radiolarian ooze of the deep Pacific Ocean (compare § 242A, and p. 1760, Note).

D. From the comparative investigations, which I have made during the last ten years into the recent deep-sea Radiolaria of the Challenger collection and the Miocene Polycystina of Barbados, it appears that about a quarter of the latter are identical with living species of the former.

{clxxvi}BIBLIOGRAPHICAL SECTION.

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