i 



THE NATIONAL INSTITUTION. 175 



distributed; Other fossils are very rare. I found a specimen of Plagiostoma du- 

 mosum (Morton) attached to an oyster-shell, which appears to be the only evidence 

 of the existence of that extinct genus in a tertiary deposit. Overlying this stratum 

 is abundance of the same Ostrea, in about three feet thickness of sand, cemented 

 by carbonate of lime. Large spscimens generally have a water-worn appearance, 

 and occur mostly in single valves ; but I found a few whole, unworn, very perfect 

 shells. The young, which are vastly abundant, are also free from any marks of 

 attrition, but are almost universally with disunited valves. 



3. The next in order is a stratum of incoherent sand, of a ferruginous color, con- 

 sisting of angular grains of quartz, and crowded with shells, in a fine state of pre- 

 servation, which, though friable, may nearly all be obtained entire, by taking time 

 and great care in collecting them. Here are about seventy genera, and rather more 

 than two hundred species of organic remains. Those bivalves which have a strong 

 ligament, as the Lucince and larger Crassatella, generally have the valves in appo. 

 sition and the cartilage still remaining. The Cylherea aquorea, which resembles 

 C. suberycinoides, (Deshayes,) the most abundant fossil at Claiborne, very seldom 

 has the valves in connection ; but if there has been any disturbance, at the time of 

 deposition, it has been insulficient to injure the most delicate angles and striae of the 

 shells. Occasionally, specimens are found which still retain their colored markings. 

 The surface of this stratum, where a portion of the sand has been washed away by 

 rain, presents the aspect of a solid bed of shells. Near the base of it, whatever 

 point was examined, a vein of soft lignite was present, and, what is remarkable, 

 certain fine large univalves appeared almost confined to this lignite, as if it had 

 been formed from vegetable substance, in the eocene ocean, to which these uni. 

 valves were partial. Beneath this lino, the sand is somewhat coherent, and many 

 species of shells are more rare, whilst others are more abundant than above it.* 



4. This stratum consists of argillaceous limestone, more or less friable, and about 

 forty-five feet in thickness. It contains a few obscure casts of shells, referable to 

 species imbedded in the sand beneath. Scutella Lyelli is the fossil of most fre- 

 quent occurrence, but is also in great abundance in the sand, whenever that is suf- 

 ficiently coherent to preserve its form. This rock somewhat resembles the newest 

 member of the cretaceous group, which I found six miles west of the village of 

 Claiborne ; but a very dissimilar group of fossils shows the difference in age at a 

 glance ; and at St. Stephens, on the Tombeckbee river, the latter passes under the 

 lower tertiary bods, as seen in the precipitous cliff. 



At the base of the Claiborne section, we observe such a group of shells as lived 

 only in the open sea. Estuary shells are more rare among them than is usual in 

 marine deposits ; for currents setting into the ocean generally carry with them the 

 dead shells of estuaries, which may be frequently observed cast up on the beaches 

 of the present seas. The eocene deposit of the Paris basin contains, it is well 

 known, one hundred and thirty-seven species of the genus Cerilhium, which clearly 

 indicate the ancient occurrence of an estuary or arm of the sea. Now, in the con- 



• In the sand I found the following fossils of the Paris basin : Solarium pntulum, (Lam.,) .S. canali- 

 eutatum, (I.am.,) BoneiUa tertbeltata, Sigaretus canaliculntus, (Sow.,) Cahjfitrcra trochiformit. (Lam.,) 

 Pyrula tncaiinata, (Lim.^ Avieula irigona, (l.a.m.,) Cijthcrea /ryr/no/f/o-, (Lam.,) Corbit Inmellesa, 

 Cnriti'a planicotta, I'ltiulana clongaln, Pectunculus pulvitiatui. 



