58 AMERICAN CORBICULAD^E. 



4O. Spliaerilim ciifoeiise, PKIME. Animal not observed. 



Shell small, transversely-oblong, very inequilateral, corn- 

 Fig. 60. pressed ; anterior side shorter, narrower, rounded ; posterior 

 broad, subtruncate ; interior margin very much curved ; 

 beaks small, not much raised ; striae barely visible, epi 

 dermis brownish-yellow with spots of a darker color. 



16 Lat * 0&amp;lt;1 Diam - 09 i 



S. cubense. 



4 ; &quot; 2} ; 2 mill. 



J7a&. Sta. Catalina de Guantanamo, Punta de la Jaula and Esperanza, 

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

 Wright, Morelet, Wheatley, and Prime.) 



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

 more compressed. 



FOSSIL SPECIES. 



41. Sphaerium recticardinale, MEEK and HAYDEN. &quot;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.&quot; 



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



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

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

 Institution.) 



Sphserium recticardinale, MEEK and HAYDEN, Proc. Acad. Nat. Sci. 

 Phila. 1860, 176. 



42. Sphaerium plaiium, MEEK and HAYDEN. &quot;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.&quot; 



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



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

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

 Institution.) 



Sphxnum planum, MEEK and HAYDEN, Proc. Acad. Nat. Sci. Phila. 

 18GO, 175. 



