GALLERY.] NATURAL HISTORY. 115 
operculum, which is entirely deficient in the other kinds. 
The animals of the genus Cymbium are ovoviviparous; the 
shell of the newly born animal is very large, and the apex 
of the spire of many of these shells is very irregularly 
twisted. 
The family of Cowries ( Cyprceadce , Case ) in the 
young state have a thin shell, covered with a thin peri- 
ostraca, and with a wide mouth like that of Bulla , but, 
as they approach the adult age, the lobe of the mantle 
spreads out so as to cover the back of the shell with two 
large lobes, which are capable of being contracted into the 
cavity of the shell at will; at the same time the mouth of 
the shell is gradually contracted and indexed, only leaving 
a narrow slit, and its back is covered with an enamel coat, 
deposited on its sides by the lobes of the mantle. The 
outer surface and edge of the lobes of the mantle are 
generally covered with various shaped and often branched 
beards. In Cyprcea , Algoa , and Ovula , the outer coat of 
the shell is polished, but in Cyprovula and Trivia it is 
covered w T ith raised ribs. In most of the genera both the 
lips are plaited, but in Ovula the inner one is smooth. 
Near this family must be placed, for the present, the 
anomalous genus Coriocella , (Case ,) which is peculiar 
among these animals for having a thin, white, ear-like shell, 
imbedded in the large expanded coriaceous mantle, which 
is nicked in front for the syphon. 
2. The Phytophagous Gasteropodes, so called because 
they live chiefly on vegetable food, are destitute of any dis¬ 
tinct syphon for the passage of water to the branchial 
cavity, and therefore have no canal in front of the mouth 
of the shell; their eggs are membranaceous, and often depo¬ 
sited on the surface of other shells ; but many of the animals 
are ovoviviparous. Many of them have a spiral oper¬ 
culum or lid, which is attached to the back of the hinder 
part of the foot of the animal: this operculum turns round 
backwards on the apex of its spire, as it increases in size, 
by the addition of new matter to the edge of its last whorl, 
so that this edge is always in the same position in the 
mouth of the shell. They are divided into sections accord¬ 
ing to the position of their eyes. 
The Podophthalmi have their eyes placed on short pedi- 
