328 KANSAS UNIVERSITY SCIENCE BULLETIN. 



polished, seal- to olive-brown, the umbones light brownish 

 drab ; posterior umboidal slope roughened and very dark 

 brown or black. Eradiate or showing the slightest traces of 

 rays. Lines of growth continuous and imbricated marginally. 

 Interior : Hinge line slightly thickened ; anterior scars 

 lightly impressed, large, often fused. Posterior scars faintly 

 marked, large, confluent. Pallial line sometimes marked. 

 Cavity of the beaks and shell deep. Nacre silver-white and 

 iridescent. 



This species is confined to the rivers of Kansas and Indian 

 Territory. In Kansas it has been reported from twenty lo- 

 calities, scattered all over the state and in all the drainage 

 areas. Its reported western range is Big creek, in Ellis county 

 (Call). The largest specimens I have seen are from the 

 Smoky Hill river at Salina. This species is not rare in any 

 of the drainage areas. 



The relation of the height to the length, the umboidal ratio 

 and the dorsal posterior marginal angle are all remarkably 

 constant in the series which I have examined. It is a slen- 

 derer species than A. grandis, and is more cylindrical and less 

 pointed posteriorly. The color of the epidermis is quite dif- 

 ferent from that of the typical grandis. The specimens re- 

 ported by Call as A. dejecta are without doubt this species. 



Anodonta opaca Lea. Plate LXXV. 



Anodonta opaca Lea, Trans. Amer. Phil. Soc. , x, 1852, p. 285, pi. xxv, 

 fig. 46. 



Shell large, thin, broadly elliptical, inflated. Anterior 

 margin rounded ; ventral margin straight or slightly bowed ; 

 posterior margin roundly biangulate, the dorsal half some- 

 times slightly incurved. Umboidal ratio, two-fifths of the 

 entire length of the shell. Umbones large, high, and much 

 inflated, marked with several concentric, nodulous, double- 

 looped ridges. Anterior and lateral umboidal slopes abruptly 

 curved ; posterior slope abrupt and often slightly incurved. 

 Epidermis smooth and shining, yellow, with a light green 



