SCAMMON : THE UNIONID^ OF KANSAS, PART I. 369 



II. Shell. Smooth. 



D. Laterals and pseudocardinals present. 

 b. Shell non-al&te. 



1. Shell thin or at most subsolid, body of shell somewhat or decidedly in- 

 flated, rays often present over the disk, pseudocardinals small, sharp- 

 pointed, erect. Iuterdentuni absent or narrow, long, and rounded. 

 I 1 . Shell with moderately high and inflated beaks, two-thirds as 

 high as long, generally yellow with greenish rays, strongly 

 dimorphic. 



a 1 . Shell small and roundly triangular. Truncilla tri- 



quetra. 

 b'. Shell large and very broadly elliptical, often stroDgly 

 truncate posteriorly. Lampsilis ventricosa. 

 2 1 . Shell with low uninflated beaks, 



a 1 , shell roundly triangular, with very erect pseudocar- 

 dinals and sharp and elevated umboidal ridge. 



aa. Shell inflated and almost circularly triangular. 



Plat/iola elegans. 

 bb. Shell rather compressed and elliptically trian- 

 gular. Plagiota donaciformis. 

 b. 1 Shell elliptical. 



aa. Shell small (not over 40 mm. in leogth), epi- 

 dermis cloth-like, beaks coarsely undulate. 



* Posterior margin rounded. Lampsilis parva. 

 ** Posterior margin pointed. Lampsilis texas- 



eosis. 

 bb. Shell large. 



* Shell very fragile and somewhat compressed, 

 pseudocardinals degenerate. 



f Shell obscurely rajed, large, generally 

 yellow, nacre pinkish. Lampsilis 

 gracilis^ 



ft Shell decidedly rayed, nacre silver 

 white. Lampsilis leptodon. 

 •* Shell thin or subsolid, pseudocardinals not de- 

 generate. 



f Shell rather broadly elliptical, with a 

 regularly rounded posterior margin. 

 % Shell subsolid, ligament quite 

 large; pseudocardinals large for 

 this group and rounded. Inter- 

 dentum present. Groupof Lamp- 

 silis ligamentina, 



XX Shell fairly thin, pseudocardinals 

 fairly pointed, ligament not large. 

 Interdentum absent or degener- 

 ate ; females greatly inflated pos- 

 teriorly. Group of Lampsilis 

 lutcola. 



tt Shell elongate, elliptical pointed pos- 

 teriorly. 



X Hhell rather compressed, eradi- 

 ate, epidermis bearing concentric 

 bands of different shades, mono- 

 morphic. Uniotetralasmus. 



XX Shell not com pressed, rays present 

 except in the very dark members ; 

 color of epidermis Dot arranged 

 concentrically; dimorphic. 



Shell rather small (not over 

 75 mm. J, seal brown, nm- 

 bones covered with many 

 fine widely V-sbaped crenu- 

 lations. Lampsilis subros* 

 trata. 



00 Shell fairly large, generally 

 polished straw color, with 

 bright green rays. Group 

 of Lampsilis fa llaciosa. 

 000 Shell very dark, polished 

 eradiate, nacre white, pink, 

 or purple. Lampsilis rrctn. 



