50 CONTRIBUTIONS 



E. rotunda. Plate 1. Fig. 17. 



Description. Shell rotund, compressed, angular above, 

 subequilateral, minutely and concentrically striate ; sub- 

 stance of the shell thick ; beaks elevated, pointed ; cica- 

 trices deeply impressed, several visible in the centre of the 

 cavity of the beaks ; cavity of the shell shallow, rugose, 

 cavity of the beaks subangular ; margin entire. 



Diam. .3, Length .9, Breadth .9, of an inch. 



Observations. The resemblance in outline between this 

 species and the nana, hereafter to be described, is very 

 great. It may be distinguished, however, from it by its 

 finer concentric striae, and its larger size. The nana is 

 always more oblique. The figure represents the usual 

 size, but it is sometimes found one third larger. 



E. inflata. Plate 1. Fig. 18. 



Description. Shell subrotund, rather transverse, inflat- 

 ed, subequilateral, very finely and concentrically striate ; 

 substance of the shell very thin ; beaks rather elevated ; 

 posterior slope furnished with an indistinct fold. Cica- 

 trices scarcely perceptible ; cavity of the shell much ex- 

 cavated, of the beak deep and rounded ; margin entire. 



Diam. .2, Length 7-20ths, Breadth 7-20ths, of an inch. 



Observations. Differs from the rotunda in being more 

 transverse, in the substance of the shell being much thin- 



