PELECYPODA—TELEODESMACEA. 573 



590. C. lintea (Conrad). Cretacic. 

 Beaks slightly incurved. Umbonal ridge more or less obscure. 



Concentric growth lines regular. 



Ripleyan of New Jersey (Cliffwood-Tinton), Gulf region. 



591. C. emmonsi (Meek). (Fig. 785, b, c.) Cretacic. 

 Surface marked with fine and obscure concentric growth lines. 



Pallial sinus short, rounded. 



Coloradoan : Kansas, Colorado, Montana ?, Utah. 



592. C. warrenana Meek and Hayden. Cretacic. 

 Differs from C. emmonsi in its larger size (average length 1.5 



inches ; height 1 inch), more convex valves, coarser concentric 

 striae, more gently rounded base and more prominent umbo. 

 Angle between cardinal borders no°. 



Montanan of Colorado-Assiniboia ; especially in the Fox Hills. 



CLXXVII. Schizodesma Gray. 



Very similar to Cymbophora but lacking the 



elevated margins of the " pit." Pallial sinus 



angular. Ligament scar connected with the 



upper part of the resilifer. Ligament and re- 



silium only slightly separated by a strong rib 



. * . 5 ' * y B Fig. 787. Schizodesma 



which has in one valve developed a small a pp ressa ^ (n. J. Pal., 

 tooth or projection and in the other an obscure I.) 

 socket to receive it. Cretacic-Recent. 



593. S. appressa Gabb. (Fig. 787.) Cretacic. 

 Beaks prominent, nearly erect. Surface concentrically striated. 

 New Jersey (Cliffwood-Wenonah), Georgia, Texas. 



CLXXVIII. Corbula Lamarck. 

 Shell ovate, very inequivalve, closed, rounded in front, contracted 

 behind. Umbones prominent. Right valve convex, the larger with 

 a strong cardinal tooth in front of the resilifer, and also a posterior 

 cardinal tooth. Left valve also with a resilifer and with one pos- 

 terior cardinal tooth. Pallial line slightly sinuous posteriorly. 

 Triassic-Recent. 



594. C. pyriformis Meek. (Fig. 788, a-d.) Cretacic. 

 Surface crossed by concentric ridges and furrows most strongly 



defined on the umbonal region ; at times only growth lines 

 present. 



