TO GEOLOGY. 201 
above and below ; substance of the shell thin; spire um- 
bilicate ; whorls compressed above; columella twisted 
and reflected at the base ; mouth linear, curved, extending 
above the spire ; outer lip sharp. 
Length 7-20ths, Breadth 3-20ths, of an inch. 
Observations. 'This species might at first view be taken 
for the St Hillairii, but may, on examination, be readily 
distinguished by its conical top. Ihave found it much 
rarer in this deposit, having been able to obtain but three 
specimens, while the other exists in great numbers. It is 
not cylindrical, like that species, but rather disposed to be 
conical above. They also differ in the base. 
Marginella biplicata. Plate 6. Fig. 216. 
Description. Shell pyramidal, transversely striate, 
emarginate at base; substance of the shell thick; spire 
elevated, pointed ; whorls four, rounded; columella with 
two large folds; mouth sniall; outer lip very thick and 
minutely crenulate within. 
Length over .1, : Breadth .J, of an inch. 
The smaller figure is of the size of nature. 
Observations. On the superior part of the whorl the 
absence of a stria makes rather a broad band, above which 
is a single stria only. This is near the suture, and on the 
superior whorls it is the only one visible. With a good 
deal of hesitation I have placed this minute shell with the 
Marginelle. Its elevated spire and emarginate base 
would seem almost to forbid its being placed with them. 
Qa 
