416 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Wm. Rogers, in his State Report on the Geology of Virginia for 

 1840. When examined under the microscope, it is found to 

 consist of an impalpable siliceous powder, derived from the cases of 

 minute animalcules. Dr. Bailey has shown that the siliceous 

 skeletons belong to several species of Navicula, Gaillonella, Ac- 

 tinocyclas, and other genera. The position of the infusorial earth, 

 the bed being perfectly conformable to the miocene strata above, 

 and the eocene below, is not decisive of its age ; but I understand 

 that the species are considered by Messrs. Tuomey, W. B. Rogers, 

 and Bailey, as implying that it belongs to the miocene formation ; 

 and Dr. Mantell, who has examined them, informs me that many of 

 them belong to living species. 



On the right bank of the James River, at City Point, Virginia, 

 about twenty miles below Richmond, in a cliff about thirty feet high, 

 I observed the yellow and white miocene sands resting on dark 

 green earth and marl of the eocene formation, just as the yellow 

 sands of the crag rest on the blue London clay in some parts of 

 the coast of Suffolk and Essex. Several miles below City Point, 

 the overlying sandy deposit contains a bed of shelly marl, some- 

 times fifteen feet thick, as at Evergreen. Here I was much struck 

 with the profusion of an Astarte {A. undulata Conrad), which 

 resembles very closely, and may possibly be merely a variety of, 

 one of the commonest and most characteristic fossils of the Suffolk 

 crag, A. bipartita. The other shells also, of the genera JYatica, 

 Fissurella, Artemis, Lucina, Chama, Pectunculus, and Pecten, 

 reminded me of shells of our crag and the French faluns, although 

 the species are almost ail distinct. The large Venus tridacnoides, 

 however, is very peculiar, and the Perna maxillata is unlike any 

 Suffolk or Touraine fossil, though closely allied to a miocene shell 

 of the Mayence basin on the Rhine. A single coral is found 

 plentifully at Evergreen, resembling an Astrea, and called by Mr. 

 Lonsdale Columnaria (?) sex-radiata. It differs from the genus 

 Astrea, as defined by Ehrenberg, in the stars not being subdivided. 

 Large flattened masses of this coral, upwards of two feet wide, were 

 lying on the beach, washed out of the marl. The teeth of sharks 

 in the banks of the James River agree, some of them specifically, 

 with those of the European miocene beds, and several cetaceous 

 bones, analogous to fossils of the Suffolk crag and Touraine faluns, 

 are frequently met with. 



On the right bank or southern coast of the river, about a mile 

 and a half south-west of Coggin's Point, a bluish green marl 

 occurs, about sixteen feet thick and not stratified, in which, assisted 

 by Mr. Rufiin, jun., I gathered in a short time more than thirty 

 species of shells, beautifully preserved, of the genera before men- 

 tioned, as also Oliva, Turritella, Teredo, Dentalium, Crassatella, 

 Corbula, Panopoea, Cyprina, Tellina, Cardita, Ostrea, and Ba- 

 lanus. The Lucina divaricata, precisely like that of Touraine, 

 or the living West Indian variety, was not rare. This deposit was 

 covered by a bed of reddish clay about six feet thick, without 

 fossils. In many places a remarkable variety of bright green 



