134 



INVERTEBRATE ANIMALS. 



our a, tail), from the fact that the end of the abdomen is 

 furnished with a long sword-like spine (Fig. 53, tf). The 

 mouth is surrounded by six pairs of appendages, the bases of 

 which are spinous and act as jaws, while their free extremities 

 are developed into nipping-claws or chelae. The whole of the 

 upper surface of the body is protected by a kind of buckler, 

 composed of an anterior semicircular shield, and a posterior 

 'somewhat hexagonal plate, the under surface of which carries 



FIG. 53. Xiphosura. Limulus poly- 

 phemus, viewed from below. 



FIG. 54. Eurypterida. Pterygotua 

 Anglicw, restored (after H. Wood- 

 ward). 



branchial plates, while the sword-like telson is jointed to its 

 hinder margin. The king-crabs attain a large size, and are 

 often called " Molucca crabs " from their occurrence in the 

 Moluccas. Both the eggs and the flesh are eaten by the 

 Malays. 



Closely allied to the king-crabs is the extinct family of the 

 Eurypterida^ an example of which is figured above (Fig. 54). 

 This species is supposed to have attained a length of probably 

 six feet, but other forms were very much smaller. 



