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THE CRAB TRIBE. 



All the animals of this tribe have their bodies 

 covered with a hard and strong shell. The head is 

 united to the thorax. or breast without any joint.' — 

 Those emphatically denominated crabs have a short 

 fiat tail, bent close to the body in a hollow betwixt 

 the legs. The Hermit- crabs, however, have a soft 

 tail, without any crustaceous covering, which the 

 animals fit into empty shells, or hollow stones. In 

 the Lobsters the tail is the principal part of the body, 

 being a very strong member, employed with great 

 advantage both in swimming and leaping. This is 

 formed of six convex segments, lying over each other 

 somewhat like the tiles of a house, and terminated 

 by five laminae, or thin plates. The former are united 

 by loose membranes, which admit of much motion. 

 At the angle, where the upper and lower parts join, 

 these segments are furnished with a kind of crusta- 

 ceous fins bordered with hair, and consisting of se- 

 veral articulations, called by naturalists pedes nata- 

 torii. The fins are moved, backward and forward, 

 and a little outward and inward, by small muscles, 

 contained within each articulation, which do not 

 differ very greatly from the real feet. By means of 

 these it is that the animals have their progressive mo- 

 tion at different depths in the water. 



Most of the Crabs have eight legs, (a few, how- 

 ever, have six or ten) besides two large claws, which 

 serve the purposes of hands. They have two eyes- 

 situated on tubercles, projecting from the head, and 



