Occasional Papers of the Museum of Zoology 7 



"Conrad gave an excellent description of U. cor. His figure 

 is poor, representing the shell as too full in the beaks and too 

 convex. It is a case of emphasizing, or in this case of 'restor- 

 ing,' a prominent feature, such as may be found in many pub- 

 lished figures. The figure, like others in the same paper, was 

 reduced, therefore drawn free-hand, and it has the faults of 

 many of Conrad's freehand figures. 



"Writing in 1834, Conrad could not be expected to so 

 describe his species as to exclude others, yet to be discovered, 

 in a numerous and difficult group. 



"The type form of U. cor has apparently not been redis- 

 covered. It has the beaks more produced than U. cdgarianus, 

 is thicker, more solid, the valves less broadly impressed, the 

 epidermis less polished. As species go in this group, it would 

 be considered distinct from cdgarianus. 



"F. apprcssa Lea has more the texture of cor, but it has a 

 less angular posterior ridge and is invariably more com- 

 pressed. This is particularly noticeable if small specimens of 

 appressa of the size of cor are compared. The somewhat 

 ebenus-like beaks of cor are another distinguishing feature. 



"F. cor is thus distinct from cdgariana and appressa as spe- 

 cies are now estimated in that group of Pleurobemas." (H. 

 A. P.) 



The localities given by Conrad for this species are the Elk 

 and Flint rivers, Alabama, both of which are in the Tennessee 

 system. 



Megalonaias gigaxtea (Barnes), 1823 



Type locality: Mississippi River, Prairie du Chien. 



Unio giganteus Barnes. '22,. p. 119 (as varietj- of U. crassus Say). 



Unio undulatus Barnes, '22. p. 120, pi. 2, f. 2. 



Unio heros Say, '29, p. 291. 



U. undithUis Bar. = U. heros Say, '31, pi. 16. 



