LIMPETS. 149 
ORDER CYCLOBRANCHIATA. 
THE breathing apparatus in this small group 
consists of a great number of little conical leaflets, 
arranged in a circle, more or less complete around 
the body, and attached beneath the margin of the 
mantle. The animal is covered by a shell varying 
much in dimensions and in structure in the different 
genera. They are all somewhat sluggish animals, 
adhering for many hours together to the surface of 
rocks, or other bodies, by means of the foot, which 
is large and muscular. All of the species inhabit 
the sea. 
FAMILY PATELLADZA. 
(Lampets.) 
A conical shell is the distinctive character of 
this family; showing no trace of a spire, and 
destitute of any aperture or notch, by which other 
genera are known, which have shells of similar 
form and appearance. The shell, which is made 
out of one entire piece, quite covers the body; it is 
in the form of a widened cone, the apex of which 
is higher or lower, nearly central, or more ap- 
proaching one end,—in different species. The 
animal is large in proportion to the shell, with 
a mantle, under the projecting edge of which, is 
a fringe of small leaves, that perform the oftice of 
respiration. The head is furnished with a large 
but short proboscis, and with two pointed tentacles, 
each of which carries an eye at the outer side of 
