103 
PLEUROTOMA. Lam. 
Gen. Cuar. An univalve, fusiform or subturreted 
shell; base of the aperture channelled; a deep 
sinus in the upper part of the outer lip. 
EE 
Tne form of the mouth in fossil shells of this Genus is 
seldom distinguishable except in the lines of growth ; the 
thinness of the outer lip renders it so liable to accidents. 
The general form is similar to that of Murex, Fusus, 
&e. The beak is straight, and the columella without 
plaits. 
PLEUROTOMA attenuata. 
TAB. CXLVI.—Fig. 1. 
Spec. Cnar. Fusiform, base attenuated; longitu- 
dinally undulated ; undulations five or six, with 
a large compressed tubercle at the upper end 
of each ; volutions transversely striated; aper- 
ture narrow, straight. 
& 
Tue upper part of each whorl is nearly even, being only 
striated and is bounded by transversely compressed tuber- 
cles on the upper part of oblique undulations or caste: 
over these and the remainder of the whorl are numerous 
small subtuberculated ridges with strie between them. 
The aperture equals half the entire length of the shell: 
the beak is produced by the gradual tapering of the last 
whorl and is of the same length as the spire; the width 
is equal to one fourth of the length; a rugged aspect is 
given by the irregular lines of growth. 
This species seems to be rare, I have only yet seen two 
pieces, found at Stubbington by Mr. Holloway. Although 
many species from that place agree with those found at 
Highgate and Barton, and the foreign ones, yet I believe 
this is found no where else. 
