286 KANSAS UNIVERSITY SCIENCE BULLETIN. 



two in the left and one (with sometimes an anterior auxiliary 

 one) in the right valve. Lateral teeth short or moderately 

 long, highest posteriorly, slightly curved, anterior adductor 

 cicatrix well impressed, large, much longer than wide, an- 

 terior retractor scar of good size, semicircular ; posterior ad- 

 ductor well marked, large, about as long as wide ; posterior 

 retractor scar large, generally distinct from the adductor 

 cicatrix. Pallial line impressed anteriorly. Dorsal scars 

 form a prominent pitted line on the under surface of the in- 

 terdentum. Cavity of beaks and shell very large. Nacre 

 satin white, iridescent dorsally and posteriorly. 



Lampsilis ventricosa var. satura Lea. Not figured. 

 Unio satur Lea, Proc. Amer. Phil. Soc, v, 1852, p. 252. 



To be distinguished from the typical species by the more 

 delicate shell, and by the darker epidermis, which often has an 

 olive-green cast. The anterior slope is generally longer and 

 the posterior more truncated than in the species proper. 



This species is found all over the Mississippi drainage and 

 in the St. Lawrence system and Nelson river and its tribu- 

 taries. The variety datura is found in the Southwest to the 

 Sabine river, Texas. It has been reported from all the main 

 rivers of the state. In the Kansas drainage system it is not 

 common. Cragin has reported it from the Kansas river, at 

 Topeka, and from Shunganunga creek, in Shawnee county. 

 Popenoe, however, has never found it in the west-central 

 part of the system in the course of his rather extensive col- 

 lecting there. In the Wakarusa river, near Lawrence, it is 

 a rare shell, and it has never been found in the Kansas at 

 that place. In the Marais des Cygnes drainage this form 

 is quite abundant, and it is still more so in the larger streams 

 of the southern area. The animal prefers deep water and a 

 muddy bed, although it is found in ripples. The distribu- 

 tion of the variety is coextensive with that of the species. As 



