NATURAL HISTORY. 
63 
GALLERY.] 
bilicated Natica, but thinner. The animal is very like Capulus , but 
the foot is divided into two parts by a deep groove ; the front part is 
narrow, concave, and strap-shaped, and the hinder orbicular and flat. 
Each of the sides is furnished with a broad wing-like membranaceous 
expansion, and the operculum is thin, horny, not shewing any spire. 
The family of Foolscap Limpets (Capuliile, Case 21) have a short 
conical body, covered with a simple conical shell, having a subspiral tip ; 
they are attached to rocks and other marine bodies like Limpets, with 
which they were formerly confounded, but they differ from them in 
their gills forming an oblique line across the back of the neck of 
animaf; their eggs, contained in the membranaceous cases, are often 
affixed in radiating groups to the side of the foot. The shells of the 
very young animal are spiral and horn coloured. In Capulus the foot 
is flat, -with a plaited front edge; in Hipponyx and Sabia , it is, as it 
were, folded on itself, and is unfit for walking upon; the back of the 
foot of the former of these animals secretes a shelly plate, marked with 
a horse-shoe shaped muscular impression, like an operculum ; and in the 
latter it forms a depression by corroding a space on the surface of the 
shell to which it is attached, of the size of its own shell, and marked 
with a crescent-shaped ridge, shewing the place where the muscles were 
affixed: the genus Brocchia only differs from Capulus in having a 
broad sinus on the right side of the aperture. The Amatliina differ from 
Capulus in having three or more strong longitudinal ridges in front._ 
The genus Pedicularia is peculiar for the apex being on one side of 
the shell, and with a different kind of surface to the margin; its animal^ 
is unknown ; it lives on coral in the Sicilian sea. All these shells adapt 
themselves to the form of the body to which they are attached; if in 
the inside of a shell they become concave outwards, and are without 
their colour, hence the genus Spiracella. 
The family of Slipper Shells ( Crepidulule, Case 21) chiefly differ 
from the former family in the body and shell being somewhat spiral, but 
they differ from most other spiral shells in the hinder lip being deeply 
concave, and furnished with a much raised edge, so as to inclose the 
whole of the foot of the animal when it is living attached to marine 
bodies like the Limpets, which they greatly resemble in their shape and 
manner of life. The shells of this family vary considerably in shape ; 
indeed, so much so that it is difficult to believe how they could be 
formed by the same kind of animals, yet, when a large series of them 
are compared, they so gradually pass one into the other that it is not 
easy to separate them even into genera. In Crepidula and Calyptroza 
the apex is spiral: in some of the latter genus the axis is perforated. 
The Trochita differ from the Calyptrcea in the lamina being only re¬ 
duced to a simple oblique plate. The Crepidula often live in groups 
attached to the outside of each other ; then the shells are very convex, 
when isolated and found on the inside of other shells they are flat or 
concave. In some species, otherwise allied to Calyptrcea, the spire is 
so reduced in length, and the lamina which separates the whorls of the 
body is so rudimentary, that nothing but the part which surrounds the 
much enlarged perforation of the axis is left ; these modifications, when 
fully developed, have been called the Cup and Saucer Limpet ( Dis - 
potea ). The Cremoria , on the other hand, have only a folded plate 
on the apex of the cavity to support the back of the body, which is 
