22 PROCEEDINGS OF THE ACADEMY OF [1880. 



Pecten Madisonius, Penia maxillata, Tellina lenis, 



" Humpbreysii, Petricola centenaria,* Venus tetrica, 



" Jeflfersonius, Plicatula marginata,* " Mortoni, 



" concentricus, Pholadomya abrupla,* " alveata, 



" Clintonius, Pholas ovalis, " inoceriformis, 



" septenarius,* {= P. costata?)* " stamineus, 



Pectunculus parilis,'^' Sazicava rugosa, " tridacnoides,* 



" lentifor- Solen ensis,* " violacea,* 



mis,* Tellina sequistriata, " Rileyi.* 



" subovatus," " biplicata, '^ 



Tbe species in italics are still living on tbe American coasts; tliose fol- 

 lowed by an * are described by Tuomey and Holmes as occurring in the 

 Pliocene formation of South Carolina. 



[Note. — The preceding table has been compiled as accnrately 

 as possible from the various papers pertaining to the paleontology 

 of the State, but owing to their number, and to the numerous 

 l)n1)lications in which they have been spread, it has proved impos- 

 sible to collect them all, and no doubt some few species will be 

 found occuriing in the State which have escaped our notice. 

 These will probably be ver}'^ few in number, and will not materially 

 affect the general conclusion. The following twenty-two species, 

 mainly those described by Say from the collection of Mr. Finch 

 (J. A. N. S., vol. iv), have no stated locality : Area centenaria, 

 A. improcera, A. incile^ Astarte distans^ Grassatella undidatd^ 

 Leda acufa^ L. conceyitrica^ L. proxima, L. Isevis^ Lucina con- 

 tracta, L. divaricala. L. subobliqua^ Panopeea rejlexa, Pecten 

 Jeff'ej'sonius, P. Clintonius, P. concentricus, P. septenarius, Pec- 

 tunculus subovatus, Plicatula marginata, Tellina sequistriata, 

 Venus deformis (tridacnoides), and V. Rileyi.'] 



It will thus be seen, that of about one hundred species of 

 bivalves, only thirty-six (36 per cent.) are common to about an 

 equal number (105) from the South Carolina deposits; and 

 further, that, whereas, of the preceding enumeration of Maryland 

 mollusca only about fifteen per cent, are recent forms, no less 

 than forty per cent, (or according to Tuomey and Holmes, nearly 

 tifty per cent.) of the South Carolina Pliocene (Conrad's Miocene) 

 bivalve mollusca are still living. There remains, therefore, no 

 question regarding the relative ages of the two formations. 



An examination of the fossiliferous strata exposed in sections 

 at various points on the western shore of Chesapeake Bay, in 



