REPORT ON THE GEOLOGY OF NORTH AMERICA. 47 



** If the deposit at Fort Washington, Maryland, be correctly- 

 referred to the eocene, it must be a newer member of that for- 

 mation than Claiborne Bluff, in as much as the species are gene- 

 rally distinct, and no secondary fossil occurs amongst them. 

 The only recent species is Venus mercetiaria (Lam.) 5 and one 

 of the most characteristic shells, Ostrea compressirostra (Say), 

 is found in the middle tertiary on James river, Virginia. Per- 

 haps the deposit at Fort Washington will be found to class itself 

 in a more recent period than the eocene." 



The total number of our eocene shells is about 210, nearly 

 all the species being from a single locality, namely, Claiborne, 

 Alabama. Other deposits, as that of St. Stephens on the Tom- 

 beckbe, present a large collection of species also, but they have 

 been found not to diifer from the species at Claiborne. 



It is remarkable enough that the older tertiary or eocene strata 

 of Alabama contain a profusion of specimens of four secondary 

 species, and yet possess not one species common with our 

 meiocene or middle tertiary. This is just the reverse of what 

 occurs among the corresponding formations in Europe, the eo- 

 cene and meiocene coalescing there by 42 common species 

 in 1238 of eocene, and the cretaceous and eocene strata having 

 nothing identical between them. From this, and the interesting 

 fact that our formations of this period contain not a single known 

 recent species, it seems pretty evident that our southern tertiary 

 strata assume an earlier place in the American eocene period 

 than the beds of the Paris basin occupy in the eocene period of 

 Europe. 



A fact equally as curious and unexpected is, that out of about 

 210 eocene fossils from Alabama, not more than six are disco- 

 vered to be common to the same period in Europe. They are, 



1. Corbis lamellosa, Lam. 



2. Cardita planicosta, Blainv. 



3. Bulimus terebellatus, Lam, 



4. Solarium patiilutn. Lam. (S. scrobiculatum, Conrad.) 



5. canaliculatum, Lam. (S. ornatum, Lea.) 



6. Fistulana elongata, Desk. 



It is not improbable, however, for reasons formerly advanced, 

 that the number of identical species will augment as our strata 

 and coast are more explored. 



Several other species show a resemblance to fossils of the 

 eocene beds of the Paris and London basins, though they are 

 obviously specifically different. 



Connected with the foregoing comparisons among our tertiary 

 shells ought to be an inquiry into the number of shells which 

 frequent our coast, and their relations to the living species of 



