nemsxks .- -'.li^ ,:.....ll species is eirtr, Tlific. A 



typical adr^ ■- '^'•^ell '-'as the following dimensiOii. : ~ i-"'"h 5.2 

 nm. ; alt., 5.5 mm.; diam, , 3.5 mm. The adiilt vr "^ x-oad- 



ly ovate, moderately inequilateral and. v/e 11- inflate , ile the 

 ^. -;l..i^- are more orbieiilar and therefore less inequilateral and usu- 

 ally have a poorly define d limule. A considerahle rarige of convex- 

 ity is noticeahle, esoecially among yoir-g valves, the most con- 

 vex valves having at the same tine higher umhones e ' lighter 

 "linge. The sharpness of the sculpture is also siihject to variation. 

 Invariably the radials are more pronouncecl toward either end. The 

 limiile is sculptured like the rest of the siirfa^e, h'--^ -ith the 

 sculpture v^ea.-rer. 



L'all (1) iiss remarked that when compared vath recent speci- 



(1). loc. Git., 1905. 



mens ^^on ohf ■./hole, the fossils are a littlu : od and 



asually more produced in front, hut these features are inconstant." 

 -his L-mecies is cha.racterised hy its small siz-e, "broadly ovate o;it- 

 line and strong, fine, i-egular sculpture. Gahh's OuaL'a Hican ""lio- 

 eene "Pse"ohi3 " caij-cellata (2) is less routed ed and less convex. 



'r). Jour. Acad. iiat. Jci., i?hiladeloMa, ' ., vol. 



37?^, pi. 47, fig. 74, 1881. 



