TO GEOLOGY. 101 
* third the length of the shell ; columella smooth, somewhat 
thickened at base; outer lip edged. 
Length 7-20ths, Breadth 3-20ths, of an inch. 
Observations. In this species, which is the largest of 
those I have noticed, the inner lip is less thickened than 
those which follow. 
P. notata. Plate 4. Fig. 80. 
Description. Shell subulate, highly polished; substance 
of the shell rather thick ; apex acute ; suture very small; 
whorls eleven, very flat, each one being marked with an 
impressed oblique line of growth ; mouth small, acutely 
angular above, about one fifth the length of the shell; colu- 
mella somewhat thickened at the base ; outer lip somewhat 
arched, with an obtuse edge. 
Length 7-20ths, Breadth .1, of an inch. 
Observations. This pretty little species is more attenu- 
ate than the preceding, and is remarkable for the slightly 
oblique lines of growth in each whorl, and which recede 
spirally from the mouth to the apex. 
P. lugubris. Plate 4. Fig. 81. 
Description. Shell rather subulate, polished; substance 
of the shell rather thin; apex rounded ; suture linear ; 
whorls seven, flattened; mouth subovate, about one fifth the 
length of the shell; columella slightly recurved at base ; 
margin thickened all round. 
Length 3-20ths, Breadth 1-20th, of an inch. 
as 
