140 SEA-SHORE LIFE 
Island and New Jersey. L. heros, Fig. 9S, ranges from Virginia to 
Labrador, and N. duplicata, Fig. 99, from Yucatan to Massachusetts 
Bay. They may be recognized by their 
large size, light yellowish-brown or bluish- 
white color, blunt, rounded spire, and sim- 
ple, round opening with a sharp-edged 
lip. In L. heros the umbillicus, or cen- 
tral cavity of the body whorl, is widely 
open whereas in N. duplicata it is practi- 
cally closed by a plug. The whole shell 
is also flatter than in L. heros. The ani- 

Fig. 99; SOUTHERN SAND- — mal is so large that when seen expanded 
COLLAR SNAIL. New Jersey. 4 . : 
it seems hardly conceivable that it could 
withdraw into its shell. However, it can perform this feat very 
rapidly, and then completely close the opening with its horny 
operculum. 
The broad, muscular foot of these snails secretes a large 
amount of mucous, enabling the creature to glide readily over the 
bottom or bury itself beneath the surface, which it always does if 
in danger of being stranded by the tide. The edges of the foot are 
sharply angular, and a large piece forward of the head is reflected 
back, making a thick, fleshy shield which serves as a ploughshare 
when the animal burrows through the sand in search of prey. The 
mantle is very contractible, and can be reflected upward over the 
shell so as to almost wholly enclose it. The surface of the shell is 
thus bathed in the secretion from the mantle, and kept smooth as 
is common with all mollusks that cover their shells in this manner. 
A notch-like fold in the free edge of the mantle admits water into 
the gill cavity. The head is provided with two sharp-pointed 
tentacles. 
These creatures are carniverous and devour other mollusks, 
including the young of their own species. They are especially 
enemies of the clams. Applying the proboscis to the surface of the 
clam shell, it bores through by means of its ribbon-like tongue, 
which is armed with numerous rasping teeth. This boring process is 
usually facilitated in carnivorous mollusks by a secretion of sul- 
pbhuric acid. The hole bored is circular, and its sides beveled as 
if countersunk, 
