REPORT ON THE RADIOLAEIA. clix 



tliem ; 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 Eadiolarian 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, pi. 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 Eadiolaria 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 Eadiolarian 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 remairas, however, the 

 siliceous skeletons of the Eadiolaria play a significant and often the most important part. Further- 

 more, 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 Eadiolarian shells (L. N. 27, 

 p. 513). At Station 303 he found " amorphous clayey matter, rounded yellow minerals, many 

 Eadiolaria-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 Eadiolaria ; and it 

 seemed as if some substance had been deposited in and on these organisms." Similar transitions 

 from well-preserved Eadiolarian shells into amorphous mineral jjarticles I have found in several other 

 specimens of Challenger soundings, and consider them a further argument for the supposition that 

 the Eadiolaria often take an important share in the formation of the red clay. 



240. List of Stations at which Eadiolaria ivere observed on the Challenger Expedition. 

 — The 168 Stations recorded below, in soundings or surface preparations from which I 

 found Eadiolaria, 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 oflicial 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 geograjihical position of the Station, 

 depth, temperature, and composition of the bottom deposit, I have added the result of my investiga- 

 tions as regards the relative abundance of the Eadiolaria in each. The five letters (A to E) denote 

 the following degrees of frequency : — A, abundant Eadiolaria (Ai, pure Eadiolarian ooze ; An, 

 mixed Eadiolarian ooze) ; B, very numerous Eadiolaria (but not a predominating quantity) ; C, many 

 Eadiolaria (medium quantity) ; D, few Eadiolaria ; E, very few Eadiolaria (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 Eadiolaria has been 

 inserted, based upon information given by John Murray in his Preliminary Eeport (L. N. 27), and 

 in the Narrative of the Cruise (L. N. 53), as well as by Henry B. Brady in his Eeport on the 



