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most frequent fossils, but it also occurs in great abundance in the 

 sand whenever that is sufficiently coherent to preserve its form. 

 2. Immediately beneath is a terrace of sandstone, about three 

 feet thick, being the upper portion of the arenaceous stratum which 

 has furnished nearly all our Eocene testacea. Over this terrace, 

 in many places, small springs of water constantly flow, falling 

 only in drops. Beneath is the incoherent quartzose sand of a 

 ferruginous color, which contains myriads of perfect but friable 

 shells, of which there are about seventy genera and rather more 

 than two hundred species. Those bivalves which have a strong 

 ligament or cartilage, as the Lncince and the larger Craasatellw, 

 generally have their valves in apposition and the cartilage still 

 occasionally remains. The Cytherea suberycinoides, (Desh.) the 

 most abundant fossil at Claiborne, very seldom has the valves in 

 connexion, but if there has been any disturbance at the time of 

 deposition, it has not been sufficient 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 

 the rains, presents the aspect of a solid bed of shells. Near the 

 base of it, whatever point was examined, a vein of very soft lig- 

 nite was observed, and what is remarkable, certain fine large uni- 

 valves appear almost exclusively confined to this lignite, as if 

 it had been formed from vegetable substance in the Eocene ocean 

 to which those univalves were partial. Beneath this line the sand 

 is somewhat coherent, and many species of shells are more abund- 

 e aiit whilst others are more rare than above it. 



In the introduction to this work, I gave the first notice of this 

 interesting locality, and referred it to the period of the London 

 clay and Calcaire yrossier, giving it a provisional name which I 

 gladly abandon since a better has been supplied in the Eocene of 

 Professor Lyell. That it is of the same, or nearly the same age, 

 I think the organic remains, described in the following pages, will 

 incontestably prove. Whether any of the species does exist or 

 not in the present ocean, I cannot pretend to decide, as our cab- 

 inets are too imperfect to admit of certainty in this point, but I 

 am unable to refer any to such recent species as have come un- 

 der my observation. None, it appears from comparison, inhabits 

 the coast of the United States, and what is more remarkable, not 

 one occurs in the Pliocene of our country. There is therefore a 

 more marked distinction between the two tertiary formations than 

 between the Eocene and Cretaceous strata, because four species 



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