﻿ANODONTA 



425 



connected with it. A. benedict cnsis is a thin, short form from 

 the lower part of the St. Lawrence System, which I regard as 

 merely a variety. 



Anouonta subgibbosa (Anthony). 



Shell irregularly ovate or elliptical, inflated, thin, somewhat 

 inequilateral, with full, high beaks having the nodulous, doub- 

 ly-looped ridges characteristic of the group : dorsal line nearly 

 straight, bounding a low wing behind ; posterior slope trun- 

 cated, the truncation meeting the dorsal line at an obtuse 

 angle ; base line curved or a little angular in the middle ; sur- 

 face rather finely, unevenly, concentrically striate ; epidermis 

 dull, ashy or ashy-green, showing the rest periods ; nacre dirty 

 bluish-white. 



Length 85, height 60, diam. 46 mm. 



Type locality. Black Lake. Michigan. 

 Anodon subgibbosa Anthony. Am. Jl. Conch.. IL 1866, p. 



144, pi. VI, fig. 2. 

 Anodonta subgibbosa P.. H. Wright, Check List. 1888. 

 Anodon subgibbosus Sowerby, Conch. Icon.. XVH, 1870, pi. 



xxviT, fig. 107. 

 Margaron (Anodonta) subglobosa Lea, Syn.. 1870, p. 81. 

 Anodonta grandis (part). Simpson, Syn.. 1900. p. 644. 



At the time of writing the Synopsis I had never seen what 

 I believed to be an authentic specimen of this species and I 

 was inclined from an examination of Anthony's figure to think 

 it was a mere form of A. grandis. Recently T have seen several 

 specimens, and I now believe that the shell is different from 

 grandis. Its high, swollen beaks are much like those of A.. 

 corpulenta, but it is very much smaller than that species, is 

 differently formed, and has not the same texture. 



Anodonta Dakota Frierson. 



"Shell elliptically rounded before (slightly cut away l)elowO : 

 dorsal line nearl\- straight ; base slightly curved. Posterior 

 nearlv straight, making the shell trapezoidal in outline. Epi- 

 dermis straw-yellow, with dark bands marking the rest periods.. 



