94 
NATURAL HISTORY. [NEW BUILDING. 
shell is also furnished with a similar slit. Another genus, 
Spiroglyphus , instead of a tube, forms a groove on the sur¬ 
face of other shells, which it covers over and converts into 
a tubular case for its body; in their young state these ani¬ 
mals assume a regular spiral form., but after a time they 
often take another direction. 
The family of Vanicoroidce appears to unite the Vermete 
to the next family; they have a cancellated white shell, some¬ 
what like an umbilicated Natica, but thinner. The ani¬ 
mal is very like Capulus, but the foot is divided into two 
parts by a deep groove ; the front part is narrow, con¬ 
cave, 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 ( Capulidce, 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 the animal; 
their eggs, contained in 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 co¬ 
loured. 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 oper¬ 
culum ; and of the latter 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 family of Slipper Shells ( Calyptrceidce , 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 fur¬ 
nished 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 
