160 
HELICIDiE. 
taken for the beating of the heart ; it is irregular, 
sometimes fast and sometimes slow. The animal is 
black, nocturnal, and subterraneous ; the mouth is 
vertical linear; the jaw small, horny, smooth or 
very minutely striated. 
The eggs are large compared to the size of the 
shell ; and this explains the bluntness of the apex, 
arising from the large size of the body of the animal, 
on which the shell is formed before it is hatched. 
Ferussac (1807) first observed that this animal was 
deprived of ocular points. (^Essai^ iii.) Nilson, in 
1822, repeated the account, and added that the apex 
of the tentacle was furnished with a small smooth 
annular depression {Moll, Suec, 29.). M. Bourge- 
gnart, on this character, has formed it into a genus. 
10. Pupa Lam, (Chrysalis Shell.) 
Animal like Bulimus^ with four club-shaped ten- 
tacles, the lower pair short, small, and with a 
cylindrical abruptly obtuse shell, with close 
pressed, gradually enlarging whorls ; the mouth 
semi-oval, mostly toothed internally; peristome 
reflexed, and interrupted behind. Jaw lunate, 
narrow, very slightly striated and crenulated. 
The young shells have a flattened front to the 
whorls, and a squarish mouth, so that they were mis- 
taken by some of the older conchologists for Trochi; 
the older whorls are more convex and rounded in 
front, and the animal does not form the reflexed lip 
until it has arrived at maturity; consequently, like 
the ClausilicB among land shells, and the Strombi 
