TO GEOLOGY. 51 
ner, and in being more inflated. The dorsal margin is 
but slightly curved. 
E. nitens. Plate 1. Fig. 19. 
Description. Shell subelliptical, obliquely transverse, 
inequilateral, the anterior portion being much the larger, 
rather compressed, smooth and shining ; substance of the 
shell very thin ; posterior slope lightly folded; beaks ele- 
vated, pointed ; cicatrices scarcely perceptible ; cavity of 
the shell not deep, of the beak rather deep ; margin entire. 
Diam. .1, Length 5-20ths, Breadth 6-20ths, of an inch. 
Observations. At first view this species might be taken 
for the inflata. On examination it will be easily distin- 
cuished by its polish, its obliquity, and particularly by the 
great disparity of the size of the anterior portion of the 
shell, the inflata being nearly equilateral. 
E. triangulata. Plate 1. Fig. 20. 
Description. Shell triangular, inequilateral, smooth, ob- 
tusely angular before, acutely angular at top, gibbous over 
the umbo—anterior to which it is flattened; substance of 
the shell rather thin ; posterior and anterior slopes flatten- 
ed; beaks elevated, pointed, incurved ; basal margin emar- 
ginate ; cicatrices not perceptible ; cavity of the shell deep 
in the superior part—of the beak deep and angular ; in- 
ferior portion of the margin finely crenulate. 
Diam..... Length .1, Breadth 1.2, inches. 
