SCAMMON : THE UNIONID.K OF KANSAS, PART I. 2^9 



ally of this form, tezasensis, probably will be found in the 

 southern rivers of the state. It is to be distinguished from 

 parva by the more pointed posterior margin. 



Lampsilis alata Say. Plate LXVIII. 



Unio alatus Say, Nich. Encyc, II, 1816, pi. IV, fig. 2. 



Shell large, subsolid, alate, slightly inflated. Anterior 

 margin rather pointedly rounded ; ventral margin straight, 

 slightly bowed ; posterior margin straight centrally, rounded 

 at the ends, set at a variable angle with the posterior margin ; 

 the upper end of the posterior margin on a level with the urn- 

 bones. Wing generally high and thin, triangular in outline. 

 Umboidal ratio very variable. Umbones depressed, orna- 

 mented with one or two minute concentric ridges. Umboidal 

 slopes flatly rounded. Epidermis smooth but with numerous 

 growth lines, which become imbricated and broken into two 

 or three shallow waves at the base of the wing. Color vari- 

 able, parrot or sage-green, horn color to chestnut brown or 

 black in old specimens ; obscure rays of dark green are present 

 in young specimens. 



Interior : Pseudocardinals generally thin, erect, serrate, 

 double in both valves ; posterior pseudocardinal the larger in 

 the right valve ; in the left valve both teeth of about equal 

 size. Lateral teeth short, gradually becoming higher and 

 thinner, posteriorly straight or very slightly curved. Anterior 

 muscle scars large, striate, deeply impressed. Posterior 

 scars large, wider than long, outlined only, confluent. Pallial 

 line impressed for a short distance anteriorly. Dorsal muscle 

 scars large and shallow, arranged in a diagonal row across the 

 urabone cavity. Cavity of umbones and shell shallow in 

 males, deep in females. Nacre purple, mauve, salmon-pink. 



The general distribution of L. alala covers all the Missis- 

 sippi valley as far south as Arkansas. In Kansas it is not 

 an abundant shell. In the Kansas drainage, the area in 



