American and English Fossil Floras. 501 



considerations present to our mind, we immediately recognize that 

 the fauna corroborates in the most striking manner what we had 

 already gathered concerning the juniority of the deposit from its 

 flora. Leaving out the Cephalopoda, about which I am not prepared 

 to express an opinion, we have a certain number of species, though 

 not known by quite the same names, which are identical with those 

 of our Gault. These are : — 



Astarte codata. 

 Gervillia silicula. 

 Scalaria Dupiniana. 



and with our Blackdown beds : — 



Fleurotomaria. 

 Cucullcea glabra. 

 Tritonidea Goepperti 



A-porrhais papilionacea (A. Mantelli 



of the Grey Chalk.) 

 Leda angidata. 



Cardium tubuUferum, 

 Trigonia alceformis. 

 Javeira. 

 Dimorphosoma anserina. 



With these is an extraordinary shell, belonging to an altogether new 

 genus of Aporrha'idcB, only represented elsewhere by a very old and 

 unique and therefore doubtful specimen from Blackdown, known as 

 A. macroptera, another large form, A. stenopterus, Goldfuss, unknown 

 in our Cretaceous, and A. granulosus, which is a nearer approach than 

 any other Cretaceous species known to me, to the recent A. pes- 

 pelicani. Among bivalves, Nucula tenera approaches, and Corbula 

 striatula, Tellina plana, T. strigata, Lncina lenticularis, L. teneris, 

 Pectuncuhis lens, species of Cardium, Venus, Cytherea and Corhida, 

 seem to be almost identical with Eocene forms. Clavagella elegans is 

 an unmistakably Eocene species. Among Gasteropoda, the numerous 

 species of Voluta, Mitra, Murex, Borsonia, Fusus, Pyrula, Turbo and 

 Bidla are all Tertiary forms unknown in British Cretaceous rocks — 

 while the Naticce, Dentalia, Cerithia and Turritellce are neutral. The 

 Cephalopoda, Inocerami and Brachiopoda are of coui'se distinctly 

 Cretaceous. A vast number of the characteristic mollusca of our 

 Gault and the Blackdown Greensaud (which has a precisely similar 

 matrix to that of the Aix-la-Chapelle beds) are absent, and their places 

 taken by a series of fusiform shells, whose nearest allies are to be 

 found in Tertiary rocks. The Danish Greensand gives similar 

 results. The Chalk with flints of Moen has, as might be expected, 

 a decidedly Chalk fauna, but with many species imknown even in 

 the newest English Chalk. 



The Coral band of Eaxo possesses no distinctly Cretaceous mollusc 

 except Pleurotomaria and a very large Aporrha'is, associated with two 

 species of Aturia, a Nautilus, and a most distinctly Eocene gi'oup of 

 Gasteropoda, including several Volutes Cyprece, Mitra, Triton, Rostel- 

 laria, Scalaria, Turbinella and Modiola. Finally the Danish lime- 

 stone called " Upper Chalk " has no purely Cretaceous genus of 

 Mollusca, but the Echinoidea are superficially not dissimilar to those 

 of our Chalk, though they may be Tertiary forms. 



A close comparison of the Mollusca has led me to infer that the 

 fauna of Blackdown itself is relatively younger than that of any of 

 the English Greensands to the east of it, and in like manner, that 

 the Chalk of Kilcorrig at the base of the formation in Ireland is 



