CRUSTACEA--LOBSTER. 781 
Order I. Decaropa.— With palpi at the mandibles, moveable eyes, and 
the head not distinct from the trunk; bronchie pyramidal, in leaflets or 
plumes, placed at the exterior base of the feet-jaws, and the feet properly 
so called, and concealed under the lateral margins of the shell. 
Order II. Sromaropa.— With palpi at the mandibles, and moveable 
eyes, but the head distinct from the trunk, and divided into two portions, 
of which the anterior bears the antenne and eyes; bronchie plumose, sus- 
pended under the tail. 
Order II]. Amputropa.—Palpi at the mandibles, and eyes immovea: 
‘ble, head distinct from the trunk, and in one piece; bronchi vesicular, 
and placed at the interior base of the feet, with the exception of the <uterior 
pair. . 
Order IV. Isopopa.— Mandibles without palpi, and the moutn a/ways 
composed of many jaws, of which the two under ones resemble a lip with 
two palpi; bronchie generally under the abdomen; feet simple, and only 
proper for locomotion or prehension; head for the most part distinct; no 
‘shell; and the eyes granulated. 
Order V. Brancutoropa.— Mouth in the form of a beak, sometimes 
eomposed of many jaws; feet in the form of fins, and the bronchie attach- 
ed between them. Body generally covered with a shell, not distinct from 
the head. 
The Crustacea are generally carnivorous, feeding on dead, or decomposed 
animal matters. Some are constantly fixed on cetaceous animals, aquatic 
reptiles, and fishes. The greater portion live in the sea, at different depths, 
and in localities proper to their various habits; others are found in fresh 
water, or on land. These which have fin-like feet, swim on their side og 
back, and the greater part of the others walk sideways or backwards. Some 
run with extreme rapidity, and others are @onstructed for climbing trees. 
Many species afford an agreeable food, and are taken for this purpose, in 
numbers, or for bait. The members of the Crustacea, when injured or disa- 
bled, are speedily reproduced, and they change their crustaceous covering 
pnnually, 
Cat LOSS tik. 
Tue lobster is an animal of so extraordinary a form, that those who first 
see it are apt to mistake the head for the tail; but it is soon discovered that 
1 Astacus marinus, Lin. The genus Astacus has four unequal antenne, the same 
transverse line, the two intermediate shortest, and deeply bifid, the lateral ones simple, 
and longer than the body, and the peduncle with squamiform teeth ; exterior feet-jaws 
long, the two first joint furnished with stiff hairs, and small spines on the internal side ; 
body oblong, subeylindrical, and the shell with a projecting beak; tail terminated by a 
fan-shaped fin ; the lateral pieces divided in two; six anterior legs didactyle, the first pair 
very long and thick, with the head more or less tuberculous, and spinous. 
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