54 CONTRIBUTIONS 
in being more equilateral. It is very common im this 
stratum. 
E. ovalis. Plate 1. Fig. 24. 
Description. Shell transversely elliptical, compressed, 
very inequilateral, furnished with two lamellar lateral 
teeth, covered with minute concentric strie, which, termi- 
nating at the anterior slope, are replaced by larger ones 
which there interlock ; substance of the shell very thin ; 
beaks small and pointed ; cavity of the shell very shallow ; 
margin entire. 
Diam. 1, Length .2, Breadth .4, ofan inch. 
Observations. This beautiful little species differs much 
from the four last described. ‘The cardinal teeth are the 
same, but this is furnished with a small lamellar tooth 
diverging on each side of the cardinal teeth. The termi- 
nation of the concentric striz, which pass from the pos- 
terior slope, interlocking with those which cover the 
anterior slope, is very remarkable. 
E. plana. Plate 1. Fig. 25. 
Description. Shell scaleniform, very compressed, trans- 
verse, very inequilateral, smooth and shining, furnished 
with two lamellar lateral teeth; substance of the shell 
very thin; beaks very small and pointed; cavity of the 
shell extremely shallow ; margin entire. 
Diam. nearly .1, Length .2, Breadth 7-20ths, of an inch. 
