58 AMERICAN CORBICULAD^. 



4:0. Spliaeriuiu ciibeiise, Pkime. — Animal not observed. 



Shell small, trausversely-oblong, very inequilateral, com- 

 Fig. CO. pressed; anterior side shorter, narrower, rounded; posterior 



ln-oad, subtruucate ; inferior margin very much curved ; 

 I'eaks small, not much raised; striae barely visible, epi- 

 dermis brownish-yellow with spots of a darker color. 

 Long. 0.16 ; Lat. 0.10 ; Diam. 0.09 inches. 

 " 4 ; " 2} ; " 2| mill. 



n<ih. Sta. Catalina de Guantanamo, Punta de la Jaixla and Esperanza, 

 Cuba, West Indies (^Jide Wright). (Cabinets of Smithsonian Institution, 

 Wright, Morelet, Wheatley, and Prime.) 



Compared with S. viridante, this species is much smaller and 

 more compressed. 



Fossil Species. 



41. SplaairiMsn recticardiiiale, Meek and Hatden. — " Shell 

 of medium size, transversely subelliptical, rather compressed, very thin ; 

 anterior side rounded ; base forming a regular semielliptic curve ; posterior 

 extremity obliquely subtruucate above and rather narrowly rounded below ; 

 cardinal margin long and straight ; beaks very small, compressed and pro- 

 jecting but slightly above the hinge, located nearly half way between the 

 middle and the anterior end ; surface marked by moderately distinct, 

 irregular lines of growth." 



Long. 0.55 ; Lat. 0.36 ; Diam. 0.24 inches. 

 Hah. Near the mouth of Grand River, on the Upper Missouri, Nebraska, 

 United Slates of America. Tertiary formation. (Cabinet of Smithsonian 

 Institution.) 



Sphxrium rccticardinale, Meek and Hayden, Proc. Acad. Nat. Sci. 

 Phila. 1860, 176. 



42. SpliaeriMm planiim, Meek and Hayden. — "Shell rather 

 small, broad oval or subcircular, much compressed ; extremities more or 

 less regularly rounded, the posterior margin being sometimes faintly sub- 

 truncate ; base semioval in outline ; cardinal margin rounding gradually 

 from near the middle ; beaks very small, compressed, and scarcely ex- 

 tending beyond the hinge-margin, nearly central ; surface marked by fine, 

 irregular, obscure concentric striae." 



Long. 0.38; Lat. 0.32; Diam. 0.08 inches. 



Hah, Near the mouth of Grand River, on the Upper Missouri, Nebraska, 

 United States of America. Tertiary formation. (Cabinet of Smithsonian 

 Institution.) 



Sphwrmm planum, Meek and Hayden, Proc. Acad. Nat. Sci. Phila. 

 1860, 175. 



I 



