ALASMODONTA CONFRAGOSA. 



SPECIFIC CHAnACTER. 



Disks with short, oblique undulations, and tuberculatcd 

 beaks. 



SYNONyM. 



Alasmodonta CONFRAGOSA. NoMs, Disscmmcdor of 

 Useful Knowledge, vol, 2, p. 339. 



DESCRIPTION. 



Shell transversly suboval, very dark or blackish : disk 

 convex, with oblique, irregular, abbreviated undulations, 

 not directed towards the beak ; and numerous, more or 

 less abl)reviated, slightly elevated lines from the umbo, be- 

 coming obsolete towards the base, those before divarica- 

 ting towards the hinge margin : beak with a gi'oove and 

 double series of three or four tubercles : luntde, or cavily 

 of the hinge membranes somewhat arquated : within 

 white, margined with opakc w hitish, or violaceous. 



OBSERVATIONS. 



This species was first obtained by Mr. O. Evans in a side 

 stream of the Wabash, called Fox river; several speci- 

 mens have been since obtained but it is rather rare. T\\v 

 teeth resemble those of the A. rugosa, Barnes, but are much 

 less prominent. On a passing glance it might almost be 

 mistaken for Unio plicatus, Nob. 



