370 KANSAS UNIVKRSITY SCIENCE BULLETIN. 



II. Shell Smooth. 



D. Laterals and pseudocardinals present, 

 b. Shell uon-alate. 



2. Shell solid, compressed, beaks low and compressed, pseudocardinals 



fairly heavy, iuterdentura present and prominent. 



a. Shell roundly triangular in outline. 



a 1 . Shell, with broad, green rays, incurved ventral margin 

 and lateral furn»w. Cyprogenia alberti, 



b 1 . Shell without lateral furrow, ventral margin not in- 

 curved. /'/<n; iota seeuris. 



b. Shell elongately ellipsoid in outline. 



a 1 . Shell broadly or narrowly ellipsoidal ; epidermis light 

 to dark brown, with tine hair rays posteriorly; beaks 

 with very fine crenulations. Groups of Phychobranchut 

 phan hi a s 



b . Shell generally narrowly elliptical; epidermis dark 

 brown or black, eradiate; beak sculptured few very- 

 coarse concentric folds: nacre white) pink, or purple. 

 / n in gibbotut, 



c. Shell quadrate, sometimes with green rays over the umbones. 



Quadrula rubiginosa, 



3. Shell roundly elliptical, triangular or quadrate, inflated in the umboidal 



region or just posterior to it. solid, pseudocardinals heavy and rag- 

 ged, the right pseudocardinal surrounded by a trench. 



a. Shell fairly solid, roundly triangular or quadrate, beaks not 



high. Group of Quadrula trigona, 



b. Shell solid, roundly elliptical, beaks not high. 



a 1 . Beaks full but not high; epidermis honey-brown with 

 sometimes a greenish cast. Obovaria ellipsis* 



!>', Beaks rather compressed ; epidermis very dark brown 

 or black. Quadt ula ebi nua. 



c. Shell roundly triangular, high, with full, high, rounded, in- 



curved beaks, very solid, with very large pseudocardinals. 

 Group of Quadrula plena, 



d. Shell suborbicular, heavy, large, with rather full, high beaks. 



Quadrula houstonensis, I This will also include the smooth, 

 circular forms of Q. pustuloses) 



gThis is intended as check on the forms of L. gracilis which have lost their ala\ 



