DESCRIPTION OP A NEW ANODONTA. 



ANODONTA VIRGATA. 



Description. 



Shell subovate, thin and fragile, inflated; umbo prominent, distant 

 from the anterior extremity; beaks pointed, incurved, undulated; um- 

 bonial slope angulated; posterior margin arcuate, extremity angulat- 

 ed; basal margin dilated posteriorly; within bluish and iridescent; 

 cavity very capacious. 



Observations. 



This pretty Anodonta is related to A. undulata, Say, but can be 

 known by the posterior dilatation of the basal margin, which inclines 

 the outline to an ovate form, and by the rays, which are very numerous 

 and unequal, of a beautiful dark green, or the epidermis is green with 

 narrow pale rays, and much resembles Anodonta radiata, nob.; it is 

 comparatively shorter than that species. 



This species was afforded me for description by Dr. Jacob Green, 

 Professor of Chemistry in Jefferson College. Mr. William Mason has 

 specimens from Buck Creek, Clarke county, Ohio. 



CONTENTS 



Plate XXI. Unio dilatatus. 

 ,, XXII. Unio tuberculatus. 



Yyjit $ Fig. 1, Unio declivis. 

 „ ^^111.^ ^ 2, Unio Blandingianus. 



,, XXIV. Unio personatus. 

 ,, XXV. Unio cordatus. 



