KING-CRABS. 



79 



Fig. 67. 



ONISCUS. 



17. Most of the Iso'pods inhabit the sea, but there 

 are some that live on land. To this order belongs 

 tiie wood-louse Oniscus {fig. 67) which is com- 

 monly found in caves, beneath stones, and in other 

 damp, shaded situations. 



18. The Sucto'ria the crusta'ceans of this divi- 

 sion are parasites, and live on other animals ; they 

 have a m<Juth in form of a beak or cylindrical 

 trunk, enclosing styliform appendages, suitable for 

 piercing the integuments of those animals whose 



fluids they suck. They are generally found attached to fishes 



19. The division 

 of crusta'ceans named 

 XI'PHOSURA forms a 

 single genus, Limulus P m 

 or king-crab. They 

 are large animals, hav- 

 ing a body divided into 

 two parts ; the first 

 part, which is covered 

 by a semicircular shield 

 or carapace, bears the 

 eyes, the antenna?, and 

 six pairs of legs which 

 surround the mouth 

 (fig. 68, 6), and at the 

 same time serve for pro- 

 gression and mastica- 

 tion, as well as for the 

 prehension of food ; the 

 second part of the body, 

 which is covered by an 

 almost triangular shield, 

 bears, underneath, five 

 pairs of natatory legs, 

 the posterior sides of 

 which are furnished 



with branchice, and is terminated by a styliform tail. These 

 singular animals are found in the Indian Ocean, and on our own 



Explanation of Fig. 67. A king-crab viewed from below : c, the cara 

 pace ; q, the tail ; b, the mouth ; pm, legs which surround the mouth ;- 

 pb, the legs bearing branchiae or gills. 



17. What are wood-lice ? 



18. What are suctorial crusta'ceans ? 



19. What are king-crabs ? How are they characterized ? 



Fig. 68. KING-CRAB LIMULUS. 



