364 KANSAS UNIVERSITY SCIENCE BULLETIN. 



is much more massive and quadrate than either of these 

 forms. The beaks of this form are more elevated than those 

 of Q. coccinea. 



The pseudocardinalsof noli da are particularly characteristic, 

 being larger in proportion to the size of the shell than any 

 other Kansas Unio. 



Quadrula plena Lea. Not figured. 



Unio plenus Lea, Trans. Amer. Phil. Soc, vm, 1843, p. 211, pi. xiv, 

 fig. 3. 



Shell large, thick particularly anteriorly, inflated in the 

 umboidal region, roundly triangular or ellipsoid in outline. 

 Anterior margin straight or slightly curved above, decidedly 

 curved below ; ventral margin straight or very slightly 

 incurved ; posterior margin curved, sometimes a little pro- 

 duced below; dorsal margin loDg, straight, oblique. Um- 

 boidal ratio, less than 0.10. Umbones very full, high, 

 incurved and recurved. Anterior umboidal slope very ab- 

 ruptly curved below, incurved above ; lateral slope moderately 

 rounded, sometimes bearing a faint, broad radial furrow ; 

 posterior slope narrow, abrupt, sometimes slightly incurved. 

 Epidermis shiny over the umbones, dark horn to black in 

 color. Lines of growth prominent. Lunule large, very va- 

 riable in shape. Ligament rather short, thick, and stout. 



Interior : Pseudocardinals low and stumpy, rough and ser- 

 rate, double in the left valve and single in the right ; anterior 

 left pseudocardinal small, often thin, posterior left pseudo- 

 cardinal a broad truncated pyramid, serrate on top; right 

 pseudocardinal the highest of the set, surrounded by trench. 

 Interdentum broad but very short ; laterals very long, slightly 

 curved, not very heavy, continued to the ligament dorso- 

 auteriorly. Anterior adductor cicatrix rather small for the 

 size of the shell, very deeply excavated, quadrant-like in out- 

 line, conliuent with the anterior retractor cicatrix ; posterior 

 scars well impressed, distinct. Pallial line impressed for its 

 anterior two-thirds. Dorsal cicatrices a line on the lower 

 surface of the interdentum. Cavity of the shell rather large, 

 of the beaks moderate. Nacre white or salmon-pink. 



