346 KANSAS UNIVERSITY SCIENCE BULLETIN. 



riety and the species are common in the Kansas river drain- 

 age, the typical variety is yet to be found there. 



The form pilsbryi was originally described as a distinct 

 species from Arkansas. Specimens of the variety from Kan- 

 sas correspond very well with specimens of pilsbryi from the 

 former state. As yet it has been reported from only two lo- 

 calities in the state — Ottawa creek, a small tributary of the 

 Marais des Cygnes, and Mill creek, in the Kansas drainage. 



This species is not particular as to habitat, and its distribu- 

 tion is entirely uninfluenced by the depth of the water in which 

 it lives ; sandy bottoms, however, are avoided. The main 

 distinctions between this and other closely related forms has 

 been already pointed out. 



Quadrula heros Say. Plate LXXX, fig. 1. 



Unio hei-os Say, New Harm. Diss., II, No. 19, 1829, p. 29. 

 Unio multiplicatus Lea, Trans. Amer. Phil. Soc, IV, 1831, p. 70, pi. IV, 

 fig. 2. 



Shell large, of moderate thickness, rhomboid in outline, 

 compressed anteriorly, somewhat inflated medianly. An- 

 terior margin flatly rounded ; ventral margin gently curved; 

 posterior margin straight except for the slight undulations 

 caused by the folds of the shell ; dorsal margin straight. 

 Umboidal ratio, 0.08 to 0.12. Umbones rather flattened and 

 sculptured, with very coarse double-looped ridges, which 

 further down the disk break up into rows of crescent-shaped 

 nodules, which extend from one-half to one-third of the dis- 

 tance down the anterior slope. Anterior and lateral slopes 

 flatly rounded ; posterior slope slightly excavated. Disk 

 ornamented with a series of oblique coarse folds, which ex- 

 tend from a line on the disk which would pass through the 

 umbones to the posterior margin. The dorsal ridges curve 

 decidedly upward to the dorsal margin. Epidermis very 

 dark brown to black. Lines of growth numerous and con- 

 tinuous and imbricated posteriorly. Ligament short, thick, 

 dark brown. 



Interior: Pseudocardinals large, high, heavy, ragged, 

 double in the left and single and sometimes double in the 

 right valve ; when double in the right the anterior tooth is 



