148 UNITED STATES GEOLOGICAL SURVEY OF THE TERRITORIES. 



incurved, and generally nearly anterior, or often overhanging the anterior 

 margin ; lunule nearly always well defined ; ligament rarely projecting above the 

 margins of the escutcheon on each side; surface marked by concentric stria-, 

 and often regular concentric ridges, which sometimes develop into strong, 

 more or less projecting varices ; hinge with three cardinal,* and one remote 

 posterior lateral teeth in each valve, the latter and the anterior tooth of the 

 left valve being cross-striate ; muscular impressions distinct; pedal muscular 

 scars disconnected from the upper ends of those of the anterior adductors ; 

 pallial line well defined, and generally a little straightened under the posterior 

 muscular impressions, but without any proper sinus. 



Fig. 9. 



Fiji. in. 



Fig. U. 



Veniella Conra&i, the type of Morton's genus. 



Fig. 1) sbows the exterior of the right valve of Morton's type-specimen, which is much fractured, but 

 the pieces have been fastened together, and the thawing made without regard to the fractures. 



Fig. 10 shows the hinge and interior of the same specimen. 



Fig. 11 drawn from a negative photograph of the last figure, and consequently shows the nature of the 

 hinge and interior of the left valve of the same species, approximately. 



This group is made to include the following sections, which may pos- 

 sibly be generically distinct: 



1. veniella, Stoliczka (— Veniliu, Morton; not of Duponchel, or Alder 

 and Hancock). 

 Shell thin, or of moderate thickness, with posterior umbonal 

 slopes prominent, angular, and imparting an angular outline to the 

 posterior basal extremity ; surface with more or less strong, concen- 

 tric ridges or varices; hinge nearly as in Cyprina, or with middle 

 tooth of left valve often more massive and. trigonal. — (Type as stated 

 ;t hove.) 



* The middle cardinal is very small, or sometimes nearly obsolete. 



