156 
HELICIDiE. 
Shell hardly a quarter of an inch long, and a third 
of its length broad, of a glossy brown or horn-colour, 
with often a reddish tinge, quite smooth and polished; 
spire composed of five or six raised volutions; aper- 
ture narrow-oval, with the margin thick and not 
reflected, often of a rosy colour. 
Varies In shape, size, and colour, sometimes trans- 
parent greenish white. 
This species was first figured as English by Lister 
{Anim. Ang. t. 2. f. 7.) and Petiver {Gaz. t. 30. f. 7.) 
8. Azeca Leach. (Trident Shell.) 
Animal like Bulimus^ with subcylindrical, rather 
obtuse shell, covered with a polished periostra- 
cum ; aperture pear-shaped, curved and pointed 
at the top; the margin thick, obtuse, and united 
all round and toothed ; the axis imperforated. 
In shape, colour, polish, and habitat, this shell so 
exactly resembles the Bulimus luhricus^ that some 
have questioned if this latter shell be not the same in 
its earlier stage of formation before the teeth appear; 
but the singular shape of the ^aperture decidedly re- 
moves it into a distinct genus, which is adopted from 
Dr. Leach. The jaw is lunate, narrow, crenulated 
on the edge. 
Mr. Alder considers this genus as intermediate 
between and Clausilia^ resembling the former 
in shape, and approaching more to the latter in having 
the peristome complete, and also more particularly in 
having a longitudinal plate on the columella, consi- 
derably within the aperture, similar in situation and 
making a slight approach in form to the clausium 
