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



II. Shell Smooth. 



D. Laterals and psendocardinals present. 

 b. Shell non-alate. 



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

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

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



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

 high as long, generally yellow with greenish rays, strongly 

 dimorphic. 



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

 cpietra. 



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

 truncate posteriorly. Lanipsilis ventricosa. 

 2'. Shell with low uninflated beaks. 



, a'. 8hell roundly triangular, with very erect pseudocar- 

 dinals and sharp and elevated umboidal ridge. 



aa. Shell inflated and almost circularly triangular. 

 Plagiola elegans. 



bb. Shell rather compressed and elliptically trian- 

 gular. Plagiola donaciformis, 

 b.» Shell elliptical. 



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

 dermis cloth-like, beaks coarsely undulate. 



* Posterior margin rounded. Lampsilis parva. 



** Posterior margin pointed. La77ipsilis texas- 

 eitsis, 



bb. Shell large. 



* Shell very fragile and somewhat compressed, 

 pseudocardinals degenerate. 



t Shell obscurely raj ed, large, generally 

 yellow, nacre pinkish. Lanipxilix 

 grficili>-.§ 



tt Shell decidedly rayed, nacre silver 

 white. Lampsilis lepiodon. 



•* Shell thin or subsolid, pseudocardinals not de- 

 generate. 



t 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. Group of Z-awp- 

 silis ligameiiUna, 



tt Shell fairly thin, pseudocardinals 

 fairly pointed, ligament notlarge. 

 Interdentum absent or degener- 

 ate ; females greatly inflated pos- 

 teriorly. Group of Lampsilis 

 luteolu. 



ft Shell elongate, elliptical pointed pos- 

 teriorly. 



t Phell rather compressed, eradi- 

 ate, epidermis bearing concentric 

 bands of different shades, mono- 

 morphic. Unioteiralasmvs. 



H Shell not compressed,rays present 

 except in the very dark members ; 

 color of epidermis not arranged 

 concentrically ; dimorphic. 



Shell rather small (not over 

 75 mm.}, seal brown, um- 

 bones covered with many 

 fine widely V-shaped crenu- 

 latioQS. 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. Lampsilisrecta. 



