Gasteropoda. MOLLUSCA. Rostrifeka. 
340 
and decayed vegetable matter, preferring nearly stag- 
nant waters, or very sluggish rivers, with a bottom of 
soft mud. The females of the American and European 
species are viviparous, and the young fry are not 
forsaken by their parent until the end of the second 
month of their existence. At first they are covered 
with spiral bands of hairs, but these soon disappear. 
The genus is represented in Plate 2, figs. 1 and 2, 
by P. hengalensis and P. costata. 
The animals of the three following families have the 
gills laminar, disposed in such a way as to form an 
oblique line across the mantle cavity, the plates or 
laminae being elongate and linear. The shells of these 
families are free and sub-spiral, with a large expanded 
mouth; and the animals are generally sedentary in 
their habits, rarely, indeed, changing their place of 
abode. 
Family— CALYPTR^ lDiE. 
Tin’s fiimlly is an extremel}'^ natural one both as 
regards the shells and the animals. The animals are 
the shell is, in external shape, like the limpet {patella ) ; 
destitute of an operculum (see Plate 2, figs. 1 and 2), and 
the apex being more or less spiral, and in the young shell 
regularly so. The aperture is wide, and the interior 
is furnished with a shelly process, variously shaped, 
and which, as Dr. Johnston observes, is a very remark- 
able structure. The animals of these shells carry and 
hatch the spawn under the neck in front of the foot. 
The eggs are inclosed in a thin membranous bag in 
small groups, and the mother “ appears literally to sit 
upon and hatch the eggs.” She disposes them under 
her belly, and preserves them, as it were imprisoned, 
between the foot and the foreign body, to which she 
adheres, “ her patelloid shell thus serving not only 
to cover and protect herself, but as a shield to her 
offspring. The young are developed under this kind 
of maternal roof, and do not quit it until they have 
strength to attach themselves to the rock, and until 
their own shell is hard enough to afford protection 
when so attached.” — {Johnston.) The species are 
numerous, about one hundred and ten having been 
described, and they are world-wide in their distribution. 
They are found adhering to stones and shells. The 
animals of most of them appear never to quit the spot 
on which they first settle, as the margins of their shells 
become adapted to the surface beneath, whilst some 
wear away the space beneath their foot, and others 
secrete a shelly base. Both the form and colour of 
the shells depend on the situation in which they grow. 
Those found in the cavities of dead shells are nearlj- 
flat, or even concave above, and colourless. They are 
presumed to feed on the sea-weed growing around 
them, or on animalcules. — {Woodward.) The internal 
testaceous appendage described above varies consider- 
ably in shape, and forms a good character for separating 
them into groups. In one this appendage is horizontal, 
covering the posterior half of the elongated aperture. 
— See Plate 2, figs. 3, 4 and 6, Crepidula dilatata and 
C. unguiformis. The shell is depressed horizontally, the 
apex being sublateral and placed somewhat posteriorly. 
These form the group of Slipper-shells, Crepidulina 
of which the genus Crepidula is the type and chief 
representative. Upwards of forty species have been 
described, the greater number of which are natives 
of South America, though several are inhabitants of 
Australia, the West Indies, the Mediterranean, China, 
and Senegal. They are sedentary on stones and shells 
in shallow water, and, according to M. Adanson, seem 
to prefer those places where the sea beats with the 
greatest violence. The)" are often found adhering to 
one another in groups of many successive generations. 
Another group have the internal testaceous appendage 
cup-shaped, ascending obliquely, and the shell conic, sub- 
spiral, with its apex superior, subcentral. These form 
the group Galerina, the “Cup and Saucer Limpets. ” — 
See Plate 2, fig. 5, Crucibulum auriculatum. In some 
oT the species of this group, as in the genus Galerus, this 
shelly plate is subspiral, lateral, and adherent. One 
of the species of this genus is British {Galerus Chi- 
nensis), and is exceedingly diversified in colour, varying 
from white, hyaline, and yellow, to reddish or dull 
violet. It varies in form also, sometimes very conical 
and smooth, at others slightly depressed, and the 
surface covered with small, arched, elevated scales. 
Sometimes it is smooth on one side and rough on the 
other. Several other modifications may be observed, 
but these must suffice. — See Plate 2, figs. 7 and 8. 
Family— CAPULID^. 
The family of Bonnet Limpets {Capulidce) are 
also destitute of an operculum, but the foot is folded 
on itself, and often seci'etes a shelly plate or forms a 
cavity in the body to which it is attached. — See Plate 
2, figs. 1 and 2, Capulus ungaricus. The shell is conical 
and cup-shaped, with a sub-spiral apex (in the young 
regularly spiral); and the interior is simple, without 
any shelly appendage. The muscular impression is 
horseshoe-shaped. The egg cases in this family 
are membranaceous, and attached in a tuft on the 
front of the foot. The animals are said to feed on 
the sea-weed that grows around them. They are 
inhabitants of nearly all the countries of the world, and 
appear to be possessed of but limited locomotion, being 
generally observed adhering to stones and other shells ; 
the margins of the aperture becoming modified accord- 
ing to the surface on which they live. 
The genus Capulus has a conical, striated shell, 
usually covered with a horny epidermis. The apex is 
posterior and spirally recurved, and the aperture is 
round and expanded. — See Plate 2, figs. 3 and 4, Capulus 
ungaricus. The animal is rather sluggish and seden- 
tary, and sometimes secretes an imperfect shelly plate 
from its foot. In the genus Hippoxyx the foot of 
the animal secretes a truly testaceous plate, which is 
adherent by its outer surface to living shells and other 
marine bodies, and leaves an impression of a horseshoe- 
shape. The shell is thick, obliquely conical, with a 
posterior apex. — See Plate 2, figs. 9 and 11 , Hipponyx 
Cornucopia. The genus Amaltiiea is represented 
in Plate 2, figs. 7 and 8. 
Passing by the three succeeding families, Valvatidce, 
Aciculidoe and Rissoellidce, we come to those species 
which have the foot round, truncated, or club-shaped. 
