CRUSTACEA-LOBSTER. 781 



Order I. Decapoda. — With palpi at the mandibles, moveable eyes, and 

 the head not distinct from the trunk; bronchia? 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. Stomapoda. — 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 antennas and eyes ; bronchia? plumose, sus- 

 pended under the tail. 



Order III. Amphipoda. — Palpi at the mandibles, and eyes immovea- 

 ble, head distinct from the trunk, and in one piece ; bronchia? vesicular, 

 and placed at the interior base of the feet, with the exception of the anterior 

 pair. 



Order IV. Isopoda. — Mandibles without palpi, and the mouth always 

 composed of many jaws, of which the two under ones resemble a lip with 

 two palpi ; bronchia? 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. Bkanchiofoda. — Mouth in the form of a beak, sometimes 

 composed of many jaws ; feet in the form of fins, and the bronchia? 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 or 

 back, and the greater part of the others walk sideways or backwards. Some 

 run with extreme rapidity, and others are constructed 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 

 annually. 



THE LOBSTER. 1 



The 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 marmus, Lint. The genus Astacus has four unequal antennae, in 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, subcylindrical, 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 

 verv long and thick, with the head more or less tuberculous, and spinous. 



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