SCAMMON : THE UNIONID^ OF KANSAS, PART I. 337 



impressed ; posterior scars large, outlined, but not impressed, 

 confluent. Dorsal cicatrices large, shallow pits in the cavity 

 of the umbones. Pallial line marked its entire length, but 

 not compressed. Cavity of the beaks slight, of the shell 

 moderately large. Branchial outlines sometimes slightly 

 marked. Nacre a silvery white. 



Unio tetralasmus var. camptodon Say. Not figured. 

 Unio camptodon Say, Amer. Conch., v, 1832, pi. xill. 

 Unio geometricus Lea, Trans. Amer. Phil. Soc, v, 1832, p. 38, pi. 

 IV, fig. 10. 



To be distinguished from the foregoing by a slightly more 

 rhomboid outline and in dull, drab-colored and cloth-like epi- 

 dermis, which is roughened by frequent coarse, continuous 

 lines of growth. Otherwise agreeing with the species proper. 



The general distribution of U. tetrala.wius is throughout the 

 Mississippi valley as far north as forty degrees latitude and 

 southwest to Mexico. It is also found in the Ohio and Ala- 

 bama river systems. 



In Kansas this species is found in all the drainage areas, 

 but perhaps most frequently in the small, muddy tributaries 

 and the large ponds and lakes of the southern drainage basin. 

 There is hardly another species which has an equal range over 

 the state ; it has been reported from as far west as Garden 

 City (Call) in the southern drainage, and as a tributary of 

 the Solomon river at Minneapolis in the Kansas area. I have 

 seen some specimens of remarkable size and beauty from 

 the latter place. It is often found in the Wakarusa river at 

 Lawrence. 



In all the material which I have gone over and have per- 

 sonally collected, I have found only one lot which could be 

 referred to the variety camptodon. This material was from a 

 pond near Thayer, Neosho county. As Doctor Call did not dis- 



*Collection Minneapolis high school. 



