230 



NEW FOSSIL SHELLS 



species at present existing; in the Miocene the proportion is small; while, in the Post- 

 Pliocene all are recent. According to Mr. Conrad, the per centage of still existing 

 shells in the Miocene is about seventeen, but I am inclined to think that it will prove, 

 on further investigation, to be smaller. It, however, cannot be relied on as a certain 

 criterion, being extremely variable in different localities. Petersburg, Virginia, may be 

 taken as an instance of one extreme : the following is a list of the fossils which have 

 been found there, exclusive of those herein described. 



Dentalium thallus, . . Con. 



" attenuatum, . Say. 



Serpula granifera, . . " 

 Balanus sp. ? 



Pholas ovalis, . . . Say. 



Panopsea reflexa, . . " 



Mactra congesta, . . Con. 



Crassatella undulata, . Say. 



" melina, . . Con. 



Corbula cuneata, . . . Say. 



" insequalis, . . " 



Tellina aequistriata, . . " 



Lucina speciosa, . . " 



" contracta, . . " 



" edentula, . . " 



" divaricata, . . Lamk. 



Astarte undulata, . . Say. 



" arata, . . . Con. 



" concentrica, . " 



Clathrodon Grayi, . . " 



Cytherea reposta, . . " 



" convexa, . . Say. 



Artemis acetabulum, . Con. 



Venus Rileyi, .... Con. 



" diftbrmis, . . . Say. 



Cardium sub-lineatum, . . Con. 



" laqueatum, . . " 



Cardita granulata, . . . Say. 

 Cypricardia arata, ... " 

 Area centenaria, . ... " 



" idonea, " 



" incile, " 



Pectunculus subovatus, . . " 

 " quinquerugatus, Con. 



" pulvinatus,* . Lamk. 



Nucula laevis, .... Say, 



" obliqua, .... " 



Chama congregata, . . . Con. 



" corticosa, ... " 

 Pecten eboreus, .... " 



" Madisonius, . . Say. 

 Plicatula marginata, . . " 



Perna torta, " 



Ostrea Virginiana? var. . Gmel. 



Capulus lugubris, . . . Con. 



Fissurella redimicula, . Say. 

 Crepidula fornicata, . . " 



" costata, . . Morton. 



Dispotaea ramosa, . . Con. 



Natica duplicata, . . Say. 



" heros? ... " 



Acteon Wetherilli, . . Lea. 

 Rotella nana, ... " 



Trochus philanthropus, Con. 

 Turritella variabilis, . " 



" indenta, . . " 



" plebeia, . . Say. 



Pleurotoma pyrenoides, Con. 

 Fasciolaria mutabilis, . " 



Pyrula carica, . . . Say. 



" canaliculata, . " 

 Fusus cinereus, ... " 



" exilis, .... Con. 



Murex quadricostatus, . Say. 



Buccinum laqueatum, . Con. 



" porcinum, . " 

 Marginella perpusilla, . " 



" liraatula, . " 



We have here sixty-eight species, in addition to one hundred and five which I shall 

 describe in this paper, and which I consider as hitherto unknown, or in all, one hundred 

 and seventy-three. Now, of these, but nine can be identified with existing shells, 

 namelv, 



Lucina divaricata, 

 Artemis acetabulum, 

 Ostrea Virginiana? 



Crepidula fornicata, 

 Natica heros?' 

 " duplicata, 



Pyrula carica, 



" canaliculata, 

 Fusus cinereus. 



and of these, two appear to me doubtful, namely, Natica heros, and Ostrea Virginiana. 

 Considering them, however, as the recent species, this gives us about five per cent, 

 of still existing shells. It appears almost absurd to compare this with the Miocene 

 of Dax, the best characterized in Europe, which, by the tables of Dr. Grateloup, con- 



* In the first number of the "Fossil Shells of the Tertiary of North America," Mr. Conrad has described and 

 figured a shell as the Pect. pulvinatus, Lam. But, after comparing it with a number of specimens of that species, 

 and with Deshayes' figures, I am forced to consider it as specifically distinct. I, therefore, propose to name it 



P. ELEPHANTOPUS. 



