CRUSTACEA. 



145 



The King-crabs (fig. 93) constitute a special group called Xiphosura 

 (Gr. xiphos, a sword ; and oura, tail), from the fact that the end of 

 the abdomen is furnished with a long sword-like spine (fig. 93, t). 

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

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

 developed into nipping-claws or cheloe. The whole of the upper sur- 



Kg. 93. — Xiphosura. Limulus poly- 

 phernvs, viewed from below. 



Fig. 94. — Eurypterida. Pterygoids 

 Atigliciis, restored. (After H. 

 Woodward.) 



face 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 branchial plates, whilst 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 sub-order of the 

 Eurypterida, an example of which is figured above (fig. 94). This 

 particular species is supposed to have attained a length of probably 

 six feet, but other forms were very much smaller. 



