PLATE LI. 



PAGE 



Fig. 1. Pteeia limula (Conrad) . . . ; 194 



Exterior of left valve. PoiDes Creek. 



Figs. 2, 2a, 3, 3a, 4. Glycymeris idoneus (Conrad) 3U4 



2. Interior of specimen. Upper Marlboro. Acad. Nat. Sci. Phila. 

 2a. Exterior of the same specimen. 



3. Exterior of larger specimen from the same locality and col- 



lection. 

 3a. Interior of the same specimen. 



4. Exterior of another specimen from Upper Marlboro. 



Figs. 5, 5a. Tkigonoaeca decisa (Conrad) var 195 



5. Interior of a right valve. Woodstock. 

 5a. Exterior of the same valve. 



303 



