TO GEOLOGY. 177 
my possession. Having been injured on a part of the 
columella, it is impossible to decide on the number of its 
folds, but presume it to be nine or ten. The front part of 
the shell is coated somewhat like a Nassa. 
MM. columba. Plate 6. Fig. 187. 
Description. Shell ovate, smooth; substance of the 
shell thick ; suture scarcely perceptible, spire somewhat 
elevated, conical; whorls , slightly convex; colu- 
mella with five folds; mouth narrow, straight ; outer lip 
much thickened, crenulate within. 
Length 7-20ths, Breadth .2, of an inch. 
Observations. Like the last described, a single individual 
only of this species came into my possession. In outline 
they resemble each other. The columba has not, how- 
ever, any deposit or coating—it has a higher spire anda 
less number of folds. The folds too are different in the 
latter, having the appearance of being formed by the 
grooving of the columella, while in the anatina they are 
placed on the columella. 
JV. crassilabra. Plate 6. Fig. 188. 
Description. Shell ovate, polished ; substance of the 
shell thick ; spire very short, pointed ; whorls four, flatten- 
ed above; columella with four folds; mouth narrow, 
somewhat curved; outer lip very thick, minutely crenu- 
late within. 
Length 7-20ths, Breadth .2, of an inch. 
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