SCAMMON : THE DNIONID.B OF KANSAS, PART I. 367 



flatly rounded and bearing a radial flattened area, which corre- 

 sponds with the radial groove present in other closely related 

 species. Posterior slope abrupt and straight. Epidermis 

 smooth and shining over the umbones, dark brown to black. 

 Lines of growth very regular, rounded, and continuous, im- 

 bricated marginally. Ligament long, high, dark brown. 

 Lunule small and narrow. 



Interior : Pseudocardinals of moderate size, low heavy, 

 ragged, double in the left and single in the right valve. The 

 anterior left pseudocardinal a low, pyramidal ridge joining 

 at a wide angle with the posterior tooth, which is an elon- 

 gate, truncately pyramidal ridge ; right pseudocardinal high 

 and ragged, surrounded by a pit. Interdentum broad and 

 long, depressed in the right valve. Laterals short, thick, 

 oblique, curved. Anterior adductor cicatrix very deep, an 

 elongate quadrant in outline; posterior scars rather small, 

 well impressed, distinct. Dorsal cicatrices on the lower sur- 

 face of the interdentum forming a line. Pallial line im- 

 pressed its entire length. Cavity of the beaks and of the 

 shell moderate. Nacre white, slightly iridescent posteriorly. 



Length. Height. Breadth. I'm. ra. 



72 55 38 0.09 (470.1) 



Q. ebenus is found throughout the Mississippi valley gen- 

 erally, except for the northwestern portion. Call reports it 

 from the Kansas river at Topeka. It is also present in the 

 Neosho river at the southern state line and at Burlington. 



The shell can be separated from the other heavy Quadrulas 

 of its type by its greater compression, less inflated and ante- 

 riorly directed beaks, and widely elliptical outline. The out- 

 line of all the nearly related forms is roundly triangular. 



Two other Quadrulas have been reported from Kansas by 

 Call (4), Q. rvbida Lea and Q. spherica Lea. As both these 

 species are confined, except for this one locality, to the eastern 

 streams flowing into the Gulf of Mexico, I withhold them 

 from this catalogue until I have more data concerning them. 

 Simpson (20) states that Call's Q. rubida is probably a some- 

 what sulcate Q. rubiginosa. 



