252 HERMIT-CRABS. MACROUROUS DECAPODS. 



closing the mouth with one of the claws, which is much larger 

 than the other, and holding to the interior so firmly, that they 

 will rather be torn asunder than quit their attachment. As they 

 increase in size, they are obliged to change their habitation for a 

 more commodious one ; and the way in which they accomplish 

 this is very amusing. They may be not unfrequently observed 

 crawling slowly along the line of empty shells, &c., left by the 

 last wave ; and as if unwilling to part with their old domicile 

 till a new one has been obtained, they slip their tails out of the 

 old house into the new one, again betaking themselves to the 

 former, if the latter is not found suitable. In this manner they 

 not unfrequently try a large number of shells, before they find one 

 to their liking. There are several species of various sizes, which 

 are inhabitants of our own shores ; they feed, for the most part, 

 upon dead fish, and all kinds of garbage thrown upon the shore. 

 The Birgus, an allied genus of tropical regions, has the tail some- 

 what more protected, but still soft ; this does not lodge in shells, 

 but retires to rocks, or hides itself in burrows in the earth. The 

 best-known species, Birgus latro, inhabits the Isle of France, 

 and lives upon cocoa-nuts ; it burrows at the roots of the trees, 

 and feeds upon the fruit which falls from them ; and it is even said 

 to climb the trunk, to obtain a further supply. 



788. The MACROTJRA, or long-tailed Decapods, are dis- 

 tinguished not merely by the length of the tail, but by having 

 it terminated by a sort of fin, expanded laterally, and consisting 

 of five pieces (Fig. 478). This is a very powerful instrument 

 for motion in water, serving, by its vertical strokes, to propel 

 the animals through the liquid ; and we consequently find the 

 Crustacea of this Section much more frequently swimming in the 

 water than walking on its bottom or on the shore. This Section 

 is a very extensive one, and contains the largest species of the 

 whole class. The Lobsters, Cray-fish, Prawns, Shrimps, &c., 

 of which the group is chiefly composed, are sufficiently well 

 known to need no description. We may notice, however, the 

 PalinuruSy or Spiny Lobster, one of the largest animals in the 

 class ; which was known to the Romans under the name of 

 Locusta. This is distinguished by the very large size of its 



