538 



MR. E. J. LECHMERE GFPPY ON THE 



reasons for believing that this submergence did not take place until 

 a late geological epoch.^ 



The following provisional arrangement of the Cretaceo-Eocene 

 deposits of Trinidad described in this paper may be suggested : — 



Miocene 



Eocene 



Cretaceous 



Eadiolarian Beds. 



Glohigerina and Nodosaria- 

 beds. 



Nucula-hQdiS. 



I 



)■ Deep-water Deposits. 



Orbitoides and Amphistegina- ^ 

 beds. 



and Echmolampas- 



Shallow-water Deposits. 



Deep-water Deposi-^s. 



beds. 

 ^ MoUusea-l eds. 

 ( Argiline of Naparima Hill, &c. 



JDitru^a-hedi of Pointapier. 

 ■{ Shaly Conglomerate, &c. ^ 



Limestone with Shells. )■ Shallow-water Deposits, 



l^ Trigonia and Ostrea-hQaB. ) 



Appendix. 



The Microscopic Structure of some Trinidad Roclcs. 

 By J. W. GREaoRT, Esq., B.Sc, E.G.S. 



Some specimens of rocks from Trinidad were submitted to me by 

 Mr. Guppy, who asked me for a few notes on their microscopic 

 structure. He gave me no information as to the horizon or strati- 

 graphical position of the specimens, as he wished merely to have a 

 quite independent description of them. 



The rocks belong to four different types : — (1) Eadiolarian Marls, 

 (2) a rock called by Mr. Guppy ' argiline,' (3) Eoraminiferal Marls, 

 and (4) a greensand sb ell-bed. 



(1) The Eadiolarian Marl of South Naparima. — This is a white, 

 soft, chalky rock, closely resembling that of the lower beds at Castle 

 Grant, Barbados, though it is whiter and the radiolaria are in better 

 preservation than is the case with the last-named. The rock 

 effervesces briskly with acid, and contains numerous foraminifera 

 (chiefly small Globigerince). Nevertheless, radiolaria, sponge-spicules, 



1 Proc. Acad. Nat. Sci. Philad. 1868, p. 313. See Ann. & Mag. Nat. Hist. 

 4 ser. vol. viii. (1871) p. 305. 



