CRUSTACEA. 



ORDER I. DECAPODA, ORDER VI. LOPHYROPODA, 

 II. STOMAPODA, VII. PHYLLOPODA, 



III. L^MODIPODA, VIII. XYPHOSURA, 



IV. AMPHIPODA, IX. SIPHONOSTOMA. 

 V. ISOPODA, 



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 pro- 

 per to their various habits ; others are found in fresh water 

 or on land. Those which have fin-like feet swim on their side 

 or back, and the greater part of the others walk sideways or back- 

 wards. Some run with extreme rapidity ; and others are con- 

 structed 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 disabled, are 

 speedily reproduced, and they change their crustaceous cover- 

 ing annually. 



ORDER I. DECAPODA. 



Branchiae in form of pyramidal leaflets or plumes near the base 

 of the last four feet-jaws and feet, and concealed under the 

 sides of the shell ; head not distinct from the trunk. 



The animals of this order have the head not distinct from the trunk, and a 

 large shell which covers all the anterior part of the body. Under this part are five 

 pairs of feet, the anterior pair generally in the form of forceps and very large. The 

 feet-jaws are applied over the mouth ; and at the upper side of the mandibles is a 

 palpus of three joints. The heart and the organs of digestion are inclosed in the tho- 

 rax, and the rectum opens at the end of the tail. The stomach is armed interiorly 

 with from three to five bony and dentated pieces, for triturating the food ; and at the 

 period of changing their shell are found two calcareous bodies, convex on one side and 

 plane on the other, called crabs' eyes, which is supposed to furnish the materials for 

 its renovation. The largest of the Crustacea and the most useful as food belong to 

 this division. 



SECTION I. BRACHYURA. (Kleistagnatha, Fab.) 

 Branchiae composed of numerous small leaflets, crowded over 

 one another along a common axis, to the number of seven on 

 each side ; post-abdomen folded or bent below, and almost 

 always received into a cavity under the pre-abdomen, not ter- 

 minated by a fin. 



The body in this section is short and broad, or at least scarcely longer than broad 

 The two anterior feet or claws are terminated by a sort of hand or forceps of two 

 fingers, of which the one is moveable. The antennae are generally small, and their 

 peduncle of three joints. The intermediate ones are folded, and lodged in a groove 



