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. 
NM. 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. 
NM. mamma. Plate 4. Fig. 95. 
Description. Shell subglobose, flattened below, smooth; 
substance of the shell thin; spire rounded at the apex, 
