SCAMMON : THE UNIONID.E OF KANSAS, PART I. 297 



posterior margin will render this an easily identified species. 

 It is interesting to note that Lea, in 1868, described a form 

 of this species from the Kansas river as Unio topekaensis . 



Lampsilis ellipsiformis Conrad. Plate LXV, fig. 1. 



Unio ellipsiformis Conrad, Monog., vm, 1836, p. 60, pi. XXXIV, fig. 1. 

 Unio spatulatus Lea, Proc. Amer. Phil. Soc, IV, 1845, p. 164. 



Shell small, subsolid elliptical, slightly inflated. Anterior 

 margin fully rounded ; ventral margin slightly bowed ; pos- 

 terior margin roundly pointed ; dorsal margin curved, curving 

 into the dorsal posterior margin. Umboidal ratio, about 

 0.30. Umbones flattened and ornamented with several 

 coarse, slightly doubly looped ridges. Umboidal slopes flatly 

 rounded, posterior umboidal ridge not sharply marked. Epi- 

 dermis smooth and shining, yellow with numerous well- 

 marked dark green rays of variable width, wavy posteriorly. 

 Lines of growth coarse, dark, and continuous. Ligament 

 stout and elongate. 



Interior : Pseudocardinals ragged, erect, bluntly pointed, 

 double in both valves ; teeth of equal size in the left valve, 

 anterior tooth the smaller in the right valve. Laterals short 

 and fairly curved. Interdentum of moderate length, narrow, 

 and rounded. Anterior adductor cicatrix well excavated, of 

 moderate size, semiellipsoid in outline ; posterior scars well 

 impressed, large, fused. Dorsal muscle scars few in number, 

 large, placed on the cavity of the beaks. Pallial line distinct 

 for the anterior two-thirds. Cavity of the shell small, of the 

 beaks very slight. Nacre white, silvery posteriorly. 



L. ellipsiformis occupies the Mississippi valley north of 

 thirty-eight degrees, and also is found in southern Canada 

 and the Red River of the North. In Kansas it has been re- 

 ported only from the Marais des Cygnes river, but seems 

 fairly well distributed up and down that stream. Its favor- 

 ite habitat is strictly mud banks. The only species with 

 which this form will be confused is the young of L. ligamen- 

 tina. It has, however, a more elongate and compressed shell 

 than have the young of that species. 



