1 8.2 BULLETIN OF THE NEW YORK STATE MUSEUM 



Unio cariosus, Say 



Fig. 8 



Beaks with six or seven undulations, which are rounded 

 and lower in front, acutely angular and elevated posteriorly. 

 First two or three minute undulations either interrupted 

 about the middle or making, at that point, a decided bend 

 toward the tip of the beak. The remaining undulations 

 make a slight bend at the middle toward the tip of the 

 beak. Anteriorly, the undulations lack converging lines, 

 but the undulations themselves continue up the anterior 

 area almost to the hinge-line. Posteriorly, the undulations 

 have converging lines, which, relatively to the strength of 

 the undulations are very weak. Dorsal areas without 

 radiating lines. 



This species is closely related to U. occidens, Lea, and 

 more remotely to U. ochraceous, Say, and U. multiradiahis. 

 The beaks are usually much eroded. Out of numerous 

 specimens from this and other localities only two had the 

 beaks perfect. Both specimens are from Norman's Kill. 

 The specimens from this locality, as a rule, have the 

 umbones better preserved than those from other localities. 

 Many can be obtained of which only the epidermis has been 

 worn off, exposing the calcareous matter of the shell, but 

 retaining the distinctive features of the undulations. 



From U. occidens, which this species resembles very 

 closely, it may be distinguished by the great difference 

 in the strength of the undulations, which are sharp on the 

 summit and very high in U. cariosus, while in U. occidens 

 they are rounded on the summit and lower. On the anterior 

 dorsal area of the two shells no difference is apparent, but 

 posteriorly the prominent converging lines of U. cariosus 

 mark an important difference. In occidens the converging 

 lines are absent or obsolescent. 



U. cariosus differs from U. multiradiatus in having the 

 undulations more widely separated one from another, and 



