228 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Ji.Il. 22, 



C. Panopaea Neocomiensis, Desk. 

 C. Thracia Phillipsii, Bom., rar. 

 c. Pholadomya Martini, Forbes. 

 c. Pholadomya, sp. 



r. , sp. 



c. Pholas constricta, Phil. 



r. Teredo, sp. 



c. Serpula articulata, Sow. 



c. filiformis, Sow. 



r. antiquata, Sow. 



C. Vermicularia Phillipsii, Earn. sp. 



R. (reversed variety). 



c. Terebratula sella, Sov). 

 i.?, Lam. 



R. Terebratulina striata, Wahl. (var. 



pentagonalis, Fhil.). 

 r. Rhynchonella sulcata. Park. 



R. lineolata, Phil. sp. 



R. , spec. nov. ? 



R. Discina, spec. nov. 

 r. Lingula truncata, Sow. 

 c. Cidaris, sp. 

 c. Pseudodiadema, sp. 

 c. Pentacrinus angulatus, lioTn. 

 r. Trochocyathus conulus ?, Phil. 



C. Wood. 



Every one who compares the foregoing list of fossils with those 

 of the Lower Greensand and its equivalents must be struck with their 

 general agreement, especially with regard to those species which are 

 most highly characteristic, and have the mdest geographical range. 

 The difference of the conditions under which the two series were 

 deposited and the distance of their localities will be amply sufficient 

 to account for the differences between their fossil contents. Pro- 

 fessor Edward Eorbes has furnished us* with an elaborate analysis 

 and comparison of the fossils of the different beds of the Lower Green- 

 sand, and has demonstrated that the whole series contains but one 

 fauna, by showing that whenever the same physical conditions are 

 repeated, the same species of fossils recur. It is this fauna which 

 we find in the highest division of the Speeton Clay ; and as the beds 

 of clay which lie at the base of the Lower Greensand most nearly 

 resemble in lithological character the beds we are describing, it 

 is of course in these (the Atherfield Clay) that we must look for 

 the closest analogies with the fossils of the Yorkshire beds. 



The relations of the Lower Greensand to various foreign deposits 

 have been so fully and ably worked out by Dr. Fitton, Professor 

 Forbes, and Mr. Godwin- Austen in this country, and by MM. 

 Romer, D'Orbigny, and D'Archiac and others on the continent, that 

 it will be quite unnecessary for me to enter upon the subject. It 

 may, however, be well to point out that this highest division of the 

 Speeton Clay appears to be altogether unrepresented in the Hilsthon 

 and Hilsconglomerat of Romer, which are, as we shall hereafter show, 

 by far the nearest continental equivalents of the second and third 

 divisions of the Yorkshire deposit. 



The name of " Etage Aptie.n^^' which was proposed by D'Orbigny 

 for beds of this age, has been generally discarded by continental 

 geologists in favour of the term " Upper ^eocomian," which is cer- 

 tainly preferable ; for I am convinced that the time is rapidly ap- 

 proaching when geologists will allow the claims of the vast series 

 of beds between the Gault and Portlandian to rank, not merely as a 

 subordinate member of the Cretaceous, but as a third Mesozoic Sys- 

 tem intermediate between the Cretaceous and Jurassic. In order to 

 avoid the glaring solecism involved in calling beds of blue clay 

 ** Lower Greensand," I have used the continental term. 

 * Quart. Journ. Geol. Soc. vol. i. (1845) p. ]94&e. 



