33 
to the same family or even genus. But it must be recollected that 
this was the case when first the study of the animal was undertaken, 
yet no one now objects to the terrestrial Helices and Bulimi being 
separated from the sea shells which were formerly arranged with 
them, or the Bulle from the other marine families, and we must ex- 
pect that the more the structure of the animal becomes known, the 
more the genera founded only on the shells will become separated 
and dispersed. 
In drawing up the characters of the suborders and families, I have 
attempted to select those which appeared most permanent, or least 
subject to variation. In all animals, as a general rule, those organs 
by which they obtain their food belong to the first class; hence the 
characters of the suborder and its divisions have been taken from the 
form of the mouth and the disposition and form of the teeth on the 
lingual membrane, as I have no doubt these parts have a most im- 
portant bearing on the ceconomy of the animal ; while the characters 
of the families have been taken from modifications of the mantle and 
differences in the structure and form of the operculum and shell ; 
for though I consider that the characters of the order, suborder, and 
families should be chiefly taken from modifications of the animal, I 
always consider that the shell and operculum are quite as important 
as regards the genus, as the animal which forms them. 
Suborder I. PRososcrprreRA. Head small, with an elongated, 
retractile, more or less exsertile proboscis, when retracted hidden 
within the body ; tentacles close together at the base or united by a 
veil over or around the base of the proboscis; eyes sessile, on the 
outer base of the tentacles; operculum annular (except in Natica). 
_ Carnivorous, eating living mollusca and other animals. 
The trunk or proboscis is of a very complicated structure, and fur- 
nished with a number of muscles, well described by Cuvier in his 
anatomy of Buccinum, which enable it to be withdrawn into itself 
like the tentacles of a snail. These animals are said to form the 
round holes so commonly found in other shells, and the lingual mem- 
brane is placed near the apex of the exserted trunk. 
In Cassidulus the head is conical, produced, annulated like a pro- 
boscis, with tentacles at the tip, close together at the base; the pro- 
boscis is completely retractile. 
Suborder II. Rostrirera. Head moderate, with a more or less 
elongated, produced, contractile, transversely annulated rostrum ; ten- 
tacles subulate, far apart on the side of the rostrum. Essentially 
phytophagous ; the rostrum is only furnished with contractile muscles, 
and varies in length and shape; in Struthiolaria it is very long and 
conical subulate, but it is not retractile like those of the former sub- 
order; the rostrum of the Stromdi is also elongated, while in some other 
families it is short and truncated, but it is always easily known from 
the retractile proboscis of the former group; the lingual membrane 
is often very long, extending far into the body of the animal. 
The families are the same as those characterized in the ‘ Figures 
of Molluscous Animals,’ vol. iv. 1850, only placed in different order, 
No. CCL.—Procrepinecs or THE ZooLoGicat Society. 
