Vol. 55.] ON THE OCSAIs'IC DEPOSITS OE TPvINIDAD. 189 



Oceana, living in the Thames estuary in 8 fathoms of muddy water, 

 conditions not precisely pelagic, he thought that the occurrence of 

 Ethmodiscus was hardly sufficient to prove that the Trinidad deposits 

 were formed far from land, in face of opposite geological evidence. 



Prof. SoLLAS remarked that, in a previous paper read before the 

 Society on the Barbadian deposits, the Authors had presented 

 convincing testimony as to the deep-sea conditions under which those 

 deposits were formed. In the present communication the argument 

 was not strengthened by the citation of Ethmodiscus. Out of a total of 

 15 species described by Count Castracane in the Challenger Report, 

 five were from the Arafura Sea, neither deep nor far from land, and 

 one from the Antarctic Ocean, at a depth of only 350 fathoms. 

 These diatoms, like others, were surface-organisms, and it was 

 difficult to understand how the depth of the sea could determine the 

 nature of the genera which inhabited its upper layers. 



Dr. Gr. J. HiNDE and Prof. Watts also spoke. 



