REPORT ON THE RADIOLARIA. 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 Nassellarta, 

 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 Philij)pines, 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 tlie enormous Pacific basin, and from 

 this as weU as from other supjjlementary observations it may with great probability be con- 

 cluded 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 difi"erent bathymetrical zones were rich in new and peculiar 

 species of Radiolaria. 



A. Many specunens 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 Eadiolaria, 

 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 " Eadiolarian ooze," e.g., 

 Stations 241 to 245, and 270, 271 (compare §§ 236-239). 



B. Pacific Eadiolarian 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. StiU the few limited spots, regarding which 



