80 
ROOM XTI. which consists of a number of cells piled one on the 
Nat, Hist, other ; and in having no terminal cavity for the recep¬ 
tion of the body of the animal. 
The remainder of the table is occupied by the shells 
of those Mollusca which live on animal food, and have 
their branchiae placed on the internal part of the man¬ 
tle, over the front of the back of the neck. 
These shells are always provided with a canal in front 
of the mouth, which covers the syphon of the mantle, 
as in the Pelican’s foot ( Aporrhais ) and the various spe¬ 
cies of Murices and Buccina. The larger species are 
used as food by the natives of the sea-coast, and 
by the fishermen as bait. In Scotland the shell of the 
large Fusus despectus is used as a lamp. The animal of 
Purpura Lapillus yields a beautiful purple colour, 
which has been considered as the Tyrian dye of the 
ancients; but there is little doubt that this colour 
was obtained from various species. The eggs of these 
animals are coriaceous, and those of the Buccinum 
undatum , and Fusus despectus have been mistaken 
for the eggs of the oyster, and called oyster-spat. 
This error is the more remarkable, as oysters , are vi¬ 
viparous, the young being found in the branchiae 
of the parent in the month of July : the egg of Pur - 
pura Lapillus has, by a similar error, been described 
as a species of Tubularia. All these eggs are in the 
collection. 
The larger species of the preceding shells are ex¬ 
tremely apt to vary according to the roughness or 
smoothness of the sea they live in ; thus, some of the 
common Whelks are thick and rugose, others Very 
thin, even, and finely coloured. Rarely the whorls of 
these shells turn contrary to the common direction, 
from left to right, and sometimes when the shell has 
been injured in its growth, the succeeding whorls are 
turned out of their usual course, and the shell becomes 
very much elongated. Most of the specimens of Fu¬ 
sus despectus are smooth, but some are spirally keeled ; 
the smaller species vary in a similar manner, but the 
differences 
