TO GEOLOGY. 109 



below the suture ; mouth semi-lunate, about two thirds 

 the length of the shell. 



Length .4, Breadth 7-20ths, of an inch. 



The figure is somewhat larger than nature. 



Observations. This species resembles the minor above 

 described, but differs from it in being more globose, the 

 spire being much more depressed. The depression of the 

 superior part of the whorl also distinguishes it. 



JV". magno-umbilicata. Plate 4. Fig. 94. 



Description. Shell subglobose, smooth ; substance of 

 the shell thin ; spire depressed, rounded ; suture small ; 

 columella very slightly thickened, the callus being small 

 and reflected above the middle of the umbilicus ; umbili- 

 cus very wide, grooved ; whorls three, inflated, with lon- 

 gitudinal folds on the superior part ; mouth semi-lunate, 

 nearly three fourths the length of the shell. 



Length .2, Breadth nearly .2, of an inch. 



Observations. A single specimen only of this species 

 has come under my examination. It most resembles the 

 minima (above described), but has a larger umbilicus. It 

 differs from all the species herein described, in having folds 

 radiating below the sutures. 



JV. mamma. Plate 4. Fig. 95. 



Description. Shell subglobose, flattened below, smooth ; 

 substance of the shell thin ; spire rounded at the apex, 



