288 KANSAS UNIVERSITY SCIENCE BULLETIN. 



The general range of Lampnilis latcola is the Mississippi 

 drainage southwest of the Brazos river, Texas, and Canada 

 east of the Rocky Mountains. It is perhaps the most abun- 

 dant and best distributed of the Kansas Unios, being a common 

 species in all the drainage basins. Its reported western limit 

 of range is the Blue river, at Manhattan ( Popenoe) , but doubt- 

 less it is to be found much farther west. I have reports of 

 its occurrence from nearly 100 localities and I never visited 

 a stream of any size in eastern Kansas along whose banks 

 there were not to be found shells of this species. 



L. luteola is a mud-loving species, and is most abundant 

 in the larger and more sluggish streams. It is found in com- 

 pany with L. anodontoides, but it does not follow that species 

 into the smaller tributaries. 



The male and female shells differ not only in the posterior 

 swelling of the valves but also in the relation of the lower 

 posterior margin to the ventral one. In the female shells the 

 angle between these two is approximately 105 degrees, in the 

 males 145 degrees. The young female shells are often enor- 

 mously distended posteriorly. 



This species is often confused with L. anodontoides. The 

 females of luteola, however, can be easily recognized by the 

 great posterior swelling, and the males by their more rounded 

 posterior margins and wide and heavy shells. 



Lampsilis powellii Lea. Not figured. 



Lea, Proc. Amer. Phil. Soc, v, 1852, p. 252; Trans. 

 Amer. Phil. Soc, v, 1853, p. 270, pi. XIX, fig. 25. 



Shell large, rather thin, elliptical in outline, neither in- 

 ll.ited nor compressed. Anterior margin almost circularly 

 rounded ; ventral margin gently and evenly bowed ; poste- 

 rior margin roundly biangulate ; dorsal margin rather long 

 and straight. Umboidal ratio in specimens examined, 0.20. 



• \n nriuMittllv swollen female. 



