344 KANSAS UNIVERSITY SCIENCE BULLETIN. 



at Oswego. Simpson (20) state sthat this form is found in 

 southern Kansas, but gives no exact localities. 



This species is shorter and higher than Q. plicate; and the 

 dorsal margin of Q. perplicata is straight and directed upward, 

 while that of Q. plicata is generally curved and directed ven- 

 trally. The rather high beaks of Q. perplicata will serve to 

 distinguish it from Q. undulata. 



Quadrula undulata Barnes. Plate LXXX, fig. 2. 



Unio undulatus Barnes, Amer. Jour. Sci., vi, 1823, p. 120, pi. n. 



Shell large, solid, thickest anteriorly, elongate quadrate 

 in outline, somewhat compressed. Anterior margin flatly 

 rounded; ventral margin gently bowed; posterior margin 

 roundly biangulate, the dorsal posterior margin being ap- 

 proximately three times the length of the ventral posterior 

 margin ; dorsal margin straight, except for the posterior third, 

 which is slightly curved. Umboidal ratio extremely variable, 

 from 0.10 to 0.30. Umbones compressed, llattened, and in- 

 curved, marked with from four to six coarse, concentric 

 ridges. Disk of the shell covered with a series of coarse 

 oblique folds, which run from the highest points of the um- 

 bones to the posterior and dorsal margins. The plications are 

 from five to eight in number, but break up considerably mar- 

 ginally. Posterior umboidal slope slightly excavated and 

 covered with a parallel series of undulations, which are di- 

 rected dorsally. The anterior of these undulations arise 

 independently on the umbones ; the posterior ones are con- 

 tinuations of the dorsal disk undulations. Epidermis chest- 

 nut brown to black in color. Lines of growth coarse, 

 numerous, continuous, imbricated posteriorly. Ligament 

 long, stout, black. Lunule long and slender. 



Interior: Pseudocardinals of moderate size, double in both 

 valves, those of the left valve high, pyramidal, ragged ; the 

 posterior of the right valve high, rough, and pyramidal, the an- 

 terior small and lamellar. Interdentum long and narrow, cut 

 away in the right valve to receive the posterior right pseudo- 

 cardinal. Laterals long, either thick or thin, slightly curved. 

 Anterior adductor cicatrix kidney-shaped, of moderate and 

 even depth, tloor roughly pitted ; protractor cicatrix large and 



