331) Gasteropoda.- MOLLUSCA. Puoboscidifeka. 
The young are large wlien born, not leaving their 
mother till they are an inch in length. Four or five 
are found in each animal. Adanson in his voyage to 
Senegal, informs us that one species of these shells, the 
“ Yets ” as they are called ( Yctus Neptuni), are thrown 
up by the high winds of April, in such quantities as 
sometimes to cover the shore, and that the animals, 
which often weigh five or six pounds, are smoked and 
preserved by the natives of Senegal against times of 
famine, to which they are frequently exposed. The 
nucleus or apex of the Yets is veiy large, callous, and 
irregular ; it is often thrown off entire. The species 
of Yetus are chiefly natives of Africa. The remainder 
of the Volutes are oviparous, the young being arranged 
in the oviduct of the female in a long string without 
egg shells. 
Genus Cymbtum. — The genus Cymbium has a ven- 
tricose shell with a short, depressed spire, which is 
frequently crowned with a diadem of strong spines. 
The aperture is very large and expanded, and the 
nucleus or apex of the shell is regularly spiral and 
persistent. The foot is not so large as in the Yets, 
and the mantle is inclosed. The surface of the shell 
is covered with a smooth, greenish-brown epidermis, 
and the shell itself usually ornamented with a variety 
of colours. Some of the species are very large, and 
thej’ are almost all natives of New Holland, and the 
great islands of the Eastern Archipelago. One or two 
of the larger, such as Cymbium a-tkiopicum and dia- 
dema, are used by the natives of these seas as vessels 
for baling the water out of their canoes. 
Genus Sc.\piia. — A number of species of Volutes, 
Instead of being ventricose, are fusiform or ovate in 
shape, and covered with a thin, smooth epidei'mis. The 
last whirl is often spinose or tubercled, and the nucleus 
is smooth or crenulated. As the shells increase in size 
the animals fill the nuclei of the spire with solid 
calcareous matter. These belong to the genus Scapha. 
They are tolerably numerous, and are principally found 
natives of the East Indian islands, though some are 
found also in Australia. Some of the shells are very 
beautiful, very elegant in form, and the rarer amongst 
them, as Scapha Junonia, for example, fetch very high 
prices. The same may bo said of ScajYia mamilla. 
Fig. 216. 
from Van Diemen’s Land, remarkable for the large 
nucleus of the spire, and the size of the shell. Specimens 
searcely exist in any other collection than that of the 
British Museum, which is peculiarly rich in this family. 
Fig. 21G represents the S. vespertilio and animal. 
Genus Voluta. — The name Voluta, as a generic 
appellation, is now restricted to a small number of 
species. The shells are of a dense structure, of an 
ovate shape, and the pillar or columella has four or five 
strongly-developed oblique plaits or folds in front, and 
several smaller transverse ones behind. The surface 
of the shell is generally ornamented with transverse 
interrupted bands and strise, so disposed as to resemble 
a bar of music. 
THE VOLUTA MUSICA or Music Shell, from the 
West Indies, has obtained its name from this circum- 
stance ; and the peculiar appearance of notes of music 
is equally v/ell exhibited in the Volnla hehraa. This 
is the onlj' genus of the family in which we find an 
operculum. It is horny, annular, and distinct. 
Genus VouyTELLA. — In the several genera we have 
briefly noticed the mantle of the animal is inclosed 
within the shell. But a considerable number of species 
are remarkable for having the lobes of the mantle 
produced, and partially covering the shell. These 
constitute the genus Volutella. In one of the most 
remarkable of the species, the Volutella angidata, 
these lobes are largely expanded, and overspread the 
spire entirely, which is generally much produced, and 
covered with a smooth, glassy deposit. In others, 
these lobes are more moderately expanded, and only 
cover the lower side of the spire, leaving a callous band 
on the suture of the upper side. Such are the fine 
large, and rather ponderous V. imperialis, with its spire 
crowned with a circle of strong spines ; the beautiful 
and elegant little V. Cymhiola, &c. 
THE DATE SHELLS, Porcellanina (genus Margi- 
ndla of Lamarck), are remarkable for the brilliancy 
and variety of their markings. The mantle lobes 
are expanded and spread over the shell, which is 
covered with a highly-polished coat laid over the epi- 
dermis. The animals are said by some to reiemble 
those of the Cowries {Cypraea), but they have the 
retractile proboscis, the lingual membrane, and dis- 
position of the teeth of the VolutidcB. The form of 
the shell also, with its conic .spire, its plaited columella, 
and its thickened outer lip, marks its relation with this 
family. The species are numerous, upwards of ninety 
having been described. They prevail more espcciallv 
along the shores of Africa, but are found also in the 
West Indies, Brazil, India, China, and Australia. They 
are quicker and more lively in their movements than 
the Cowries, crawling pretty briskly', and moving their 
tentacles in different directions. The foot of the animal 
appears to be double-edged in front, and this part is 
said by Mr. A. Adams, who has had opportunities of 
seeing some of the species in their native localities, to 
be endowed with acute sensation, the animal making 
use of these two portions of the body as feelers. Their 
favourite locality is shallow water on clear sands; and 
when seen in full activity, they are said to be objects 
of singular interest and beauty. 
Family— CASS! DIDfE. 
The family of HELMET SHELLS {Cassididn’) 
the foot largely dilated ; and the operculum, which it 
bears near its posterior extremitj', is annular, ovate, or 
