CRUSTACEA. 



Apus Productus. 



Birgus Latro. 



Atya Scabra. 



Birgus Latro is a long tailed crustaceous animal approaching the Hermit Crab. Of this genus the middle 

 antennse have their second articulation tufted by pincers ; the feet of the first pair of legs are unequal and 

 terminated by pincers ; the feet of the second and third pair end in a single nail ; and the tail is round. 



They are natives of Amboyna and the neighboring islands. Wherever they may be, they journey once 

 a year to the sea, and after their return, they hide themselves in the earth for six weeks, so that not one 

 is seen. During this period, like other crabs, they doff the old shell and gain a new one. They are said 

 to be most delicious eating, just after casting their old crust. 



The number of legs possessed by the Crustacea is greater than that of perfect insects, being never less 

 than four pairs, besides the pair of claws which may be considered as metamorphosed legs. It is in the 

 crab, lobster, cray-fish, &c, that we find this small number; and these belong to the highest order, the 

 Decapoda, or ten-footed Crustacea. In front of these are some curious organs termed feet-jaws, being 

 intermediate in structure between these two kinds of appendages ; in some of the lower Crustacea these 

 become true legs. And from the posterior part of the body there hang down certain appendages, which 

 are also true legs in the lower orders. In fact, the lowest Crustacea approach very closely to the Myria- 

 poda in their general form and structure, differing chiefly in their aquatic mode of life ; the segments of the 

 body are nearly equal, and are each furnished with a pair of legs. On the other hand, among the Deca- 

 pods we find an approximation to the form both of insects and spiders — the lobster representing the one, 

 and the crab the other. In the lobster we have a regular division into head, thorax, and abdomen, as in 

 insects ; and it is to the thorax alone that the locomotive appendages are attached, as in the perfect state 

 of the insect. As in all other Articulata, the eyes of the Crustacea are compound. Their external coating 

 is thrown off with the shell ; and this, when examined with the microscope, is seen to exhibit the division 

 into minute lenses with beautiful distinctness. 



Lobster. 

 (365) 



Shrimp. 

 31* 



Crab. 



