108 THE AMERICAN MONTHLY [Apr 



radiatus of Gr. von Ehrenberg. But Coscinodiscus radiatus 

 is a more recent form than Coscinodiscus asteromphalus, 

 so that they must accordingly all be referred to that form. 

 , Synedra jeffreysii is the sanie as Synedra thalassiothrix 

 P.D.C. (1873. Diatoms from the Arctic Sea, p. 22. PL 4, 

 Fig. 24). It includes the genus Thalassiothrix. This is 

 found in the Mediteranean at Rimini and Fans, and at 

 the Nicobar Islands. Ethmodiscus is but a form of Cos- 

 inodiscus, perhaps C. asteromphalus, and both of these 

 Cosinodiscus and Synedra jeffreysii are common in the 

 Pacific coast Infusorial stratum. C. asteromphalus also in- 

 cludes C. craspedodiseus, E. O'M. (Quar. Jour. Mic. 

 Soc„ Vol. XVII. p. 561), as well as C moseleyii, E. O'M. 

 (Jour. Lin. Soc. Lond., Vol. XV. p. 57, pi. 1, Fig. 6); and 

 C. arrapurensis E. O'M. (Quat. Journ. Micro. Sci. 1877. 

 p. 463); and C. arapurensi8,E. 0'M.(Var. no v. Cast. Chall 

 1886. p. 153, pi. 11. Fig. 4.) C. centralis C. GK E. (Var. 

 nov. Cast. Chall. 1886. p. 155, pi. 11. Fig. 3.); C. mini- 

 ficus F. C. (1886. Chall. p. 154, pi. 11. Fig. 6,) and C. 

 papuanus F. C. (1886. Chall. p. 154. pi. Ill, Fig. 8). 



In his preliminary notes on the nature of the sea bot- 

 tom pronounced by the soundings of H. M. S. "Challen- 

 ger" during her cruise in the 'Southern Sea' in the early 

 part of the year 1874 (Proc.Roy. Soc. Nov. 26, 1874, p.47). 



Professor C. Wyville Thomson says : "On the 11th of 

 February, lat. 60° 52' S., long. 80° 20'. E., and on March 

 3d lat. 53° 55' S., long. 108° 35' E., the soundings came 

 up filled with a fine cream-colored paste, which icarcely 

 effervesced with acid, and discolor into a very light im- 

 palpable white power. This, when examined under the 

 microscope, was found to consist entirely of the frustules 

 of diatoms, some of which were wonderfully perfect in 

 all the details of their ornament, and many of them were 

 broken up. The species of diatoms entering into this 

 deposit have not yet been worked up but they appeared 

 to be referrable chiefly to the genera Fragillaria Coscin- 



