162 Tertiary. 



fossils ave frequently water-worn, always with disunited valves, and 

 appear to have been transported. Occasional!}' a specimen occurs not 

 in .the least abraded, a circumstance which indicates the vicinity of 

 the Petersburg deposits to the mouth of the river. The strata occur in 

 a meadow, and consist of blue marl, of a sandy texture, often inter- 

 mixed Avith small gravel and ferruginous sand, full of shells ; there is 

 here also a proportion of gravel, of rounded quartz, occasionally of 

 large size. Water-worn fragments of bivalves are abundantly inter- 

 mingled with entire shells, and many species occur with connected 

 valves. This is particularlj^ the case with the burrowing shells, as 

 Panopoia, but also, though less frequently, with the large Venus tri- 

 dacnoides, Crassatella undidata, Astarte concentrica, Cytherea al- 

 haria, two species of Chama^ and even two species of Ostrea are not 

 uncommon; but there is nothing like an 03'ster bed in these strata 

 which might indicate shoal water. The proportion of oysters to the 

 other bivalves is about the same which the dredge furnished at the 

 mouth of Cape Fear river, North Carolina, at the depth of eight 

 fathoms. 



In 1844, Prof. J. W. Bailey* identified numerous living Infusorial 

 forms with the fossil Infusoria, from the Miocene at Petersburg, Va., 

 and Piscataway, Md., and described several new species. 



Mr. Conradf described, from the Miocene, at Petersburg, Va., Crepi- 

 duJa cymbceformis ; from the Eocene at Marlbourne, Hanover count}'. 

 Va., Cytherea eversa, C. liciata, C. subimpressa; from Stafford count}^ 

 Va., C pyga ; from Claiborne, Ala., Cardita densata ; and from near 

 Santee, South Carolina, Pecten elixatus. 



Dr. Edmund Ravenel described, from the Miocene of South Carolina, 

 Peoten mortoni ; from the Eocene, Terebratula canipes, and Scutella 

 pileussinensis, now Mortonia pileussinensls. And Dr. Robert W. 

 Gibbes described, from a bed of green sand near the Santee canal, and 

 about three miles from the head waters of Cooper river, South Carolina, 

 Dorudon serratus.\ 



In 1845, Prof. James Hall§ described, from Tertiary, slat}-, bitumin- 

 ous limestone, on the dividing ridge between the waters of Mudd}^ 

 river flowing eastward, and those of Muddy creek flowing into Bear 

 river on the west, in long. Ill deg., lat. 40 deg., 3fya tellinoicles, 



'■■' Am. Jour. Sci. and Arts, vol. xlvi. 

 t Proe. Acad. Nat. Sci., vol. ii. 



X This species was errontously mentioned as Cretaceous on page 15, vol. iii,. of this 

 .Journal, or page 51 of this article. 

 ^ Fremont's Expl. Exped. 



