LOBSTER, SPIDER-CRAB. 195 



into oars, by the help of which these Crabs swim with 

 great ease, while the formation of their other legs per- 

 mits of their crawling with equal facility when they 

 desire it. In the Lobster, and all the long-tailed Crus- 

 tacea, such as the various kinds of Shrimp and Prawn, 

 the tail is the chief instrument of locomotion. Owing 

 to the form of the body, these animals, notwithstanding 

 their well-developed legs, make but slow work of it when 

 they attempt to crawl. But nothing can exceed their 

 activity in swimming or, more properly, in darting 

 backwards through the water. The rapid motions of 

 a Shrimp or Prawn must be familiar to every sea-side 

 visitant. Those of a Lobster, though less frequently seen, 

 are equally rapid, and both are effected in the same 

 manner. The tail in these animals is furnished at its 

 extremity with a number of broad flat plates, so placed 

 as to close together when this organ is extended, and to 

 open and present a broad fan to the water on every 

 downward stroke. The lobster turns his back, which is 

 smooth and rounded, so as to present little resistance to 

 the water, in the direction in which he wishes to move, 

 and then by a vigorous stroke of the tail, whose front, 

 presented to the water, is concave, and its extremity 

 furnished with a spreading fan, he can dart backwards 

 to the distance of eighteen or twenty feet. 



Among the Crabs which one commonly meets with in 

 dredging are several kinds, belonging to more than one 

 modern genus, to which the popular name of Spider-Crab 

 is given. These are all characterized by having long 

 and slender legs like those of Spiders, and generally a 

 triangular body, more or less pointed, or produced into a 



