92 Palabontographica Americana 92 



PIvATE XII 



Figure Page 



1. Area subrostrata Conrad S' 



Miocene of Plum Point, Maryland; a valve with finely divided ribs. The pos- 

 terior ribbing is obscured by the illumination. 



2. Interior of the same. 



3. Area subrostrata Conrad; Miocene of Plum Point, Maryland; a valve with nodu- 

 lous ribs. 



Area subrostrata Canrad; Miocene of Plum Point, Maryland; right valve with 

 rather narrow ribs. The posterior ribbing is obscured by the light. 

 Area elnia Glenn Si 



"Exterior of right valve. Jones Wharf"; after Glenn. 



6. Area ebiia QAqxvo.; "Interior of right valve. Same locality" ; after Glenn. 



7. Area clisea Dall 52 



Miocene of North Carolina. The posterior margin is broken. 

 Area eliseaXid^A; "Miocene of Virginia; 56 mm."; after Dall. 



Area aresta Dall S3 



Miocene of the upper bed at Alum Bluff, Florida. 



10. Umbonal view of the same. 



11. Area aresta Dall; Miocene of Alum BlufE, Florida; interior of a younger valve, with 

 less attenuated posterior end. 



12. A rea ca mpsa Dall 54 



Miocene of Alum Bluff, Florida; figured to show the form of the young. 



