of Tin: geni - i mi. 265 



It is evident, that the word explained by (the former ot 

 these definitions is the most proper to express g genus oi 

 shells: and consequently, in Ckmchotogy, the word Hwo is 

 niascnline. 



1. Unio Calceolus. Plate III. fig. l. 



Tc*r; imrrniiUi/vrali, transversa, aliqwmtulbm cyl tenuitei 



rugalti ; dente cardinali prominente. 



Shell inequilateral, transverse, somewhat cylindrical, finely wrinkled : 

 cardinal tootli prominent. 



Hah. Ohio. T. G. Lea. 



My Cabinet 



Cabinet of Prof. Vanuxem. 



Diam. -6, Length -S, Breadth 1-5 inches. 



Shell ventricose, cylindrical, transverse — substance of the 

 shell thin, rather thicker anteriorly — beaks slightly elevated, 

 undulated and touching: not decorticated — ligament short, 

 partly concealed by the beaks — dona] margin straighl : pos- 

 terior dorsal margin oblique and carinated; posterior margin 

 angular; posterior basal margin curved ; basal mar gin nearly 

 straight ; anterior and anterior dorsal and basil margins round- 

 eel — epidermis dark green at the margin and becoming lighter 

 towards the beaks; rays indistinct — cardinal tooth of right 

 valve prominenl and somewhat pointed; the single tooth of 

 this valve shuts in before the tooth of the left valve, instead of 

 passing into i< ; the tooth of the latter valve is emarginate — 

 lateral tooth very short and single in both valves — posterior 

 cicatrices confluent, as are also the anterior ones — cavity of 

 the beaks deep — nacre pearly, white and silvery, iridescent in 

 the posterior margin. 



Bemarto. — This curious little shell is peculiar in its promi 

 n. ni curved tooth, shutting in before that, of the other ralvt 



\ oi.. in. — i \ 



