86 
NATURAL HISTORY. [NEW BUILDING. 
often spread out, and sometimes divided into lobes, like 
the Pteroceras, or Spider-claws. 
The family of Buccinums ( Baccinidce , Cases 8—11) have 
the syphon of the mantle recurved, and the shell has a 
more or less elongated canal in the front of the mouth for 
its protection, which is bent upwards towards the left 
side. Some of these animals form convex rounded va¬ 
rices at distant places on the whorls, like the Tritons, 
and generally have the lips veined or granular, as Cassis, 
Cassidaria , Dolium, and Harpa. The latter has a very 
large foot, nicked on each side in front, and pointed 
behind; its hinder part separates spontaneously when 
the animal is irritated. Others, like the Mur ices, have 
close irregular varices, which are sometimes produced into 
spines or branched processes, as Ricinula, Purpura, and 
Magilus . The latter is very peculiar; for the animal, at 
a certain period of its growth, deposits in the cavity such 
a quantity of calcareous matter, as to produce the shell, in its 
subsequent growth, into a more or less elongated straight 
process. In others the animal does not form any, or only very 
rudimentary, varices, as Buccinum , Terebra, Nassa, and 
Columbella, and the shells are covered with a horny pe- 
riostraca. These genera are severally distinguished from 
each other by the form of the mouth ; some of them, which 
have the lips much dilated over the base of the last whorl, 
have a very large foot, which is believed to secrete the 
shelly matter of which the lips are formed. Xhe Nassce 
have a moderate sized foot, which is nicked behind, and 
the operculum is toothed on its edge. The Bullice re¬ 
semble them in most characters, but they have a very 
large broad foot, and the hinder part of the inner lip of 
the shell, being extended beyond the mouth, forms a 
raised enamel band round the suture of the whorls, as is 
also the case with the Ancillarice and some Volutes; 
Phos and Cyllene have a small sinus in the front of the outer 
lip, like the Strombs . The Olives have the shell covered 
with a polished coat, and sunk into the large expanded 
foot, so that only a small part of its back can be seen 
when the animal is walking; the front of the foot is se¬ 
parated from the hinder part, as in the Volutes, by a 
deep nick on each side, and the front of the pillar of the 
shell is obscurely plaited. The true Olives {Oliva) have 
