264 



SECTION C. 

 ORDER VI. XYPHOSURA. 



875. Although this group only contains a single genus, the 

 Limulus, or King-crab, yet the structure of this departs so 

 widely from that of all the Crustacea we have hitherto con- 

 sidered, that it cannot be referred to the same Order, or even 

 the same Sub-Class, with any of them. The Limuli, which are 

 Crustacea of considerable size, sometimes attaining the length of 

 two feet, have their bodies divided into two parts ; of which 

 the anterior, covered by a large semicircular shield (c, Fig. 598), 

 bears the eyes, the antennae, and six pairs of legs, which sur- 



TIG. 597. LIMULUS. 



FIG. 598. UND] R SURFACE OF LlMULUS. 



round the mouth (), and are used both for walking and for 

 mastication ; whilst the posterior portion of the body, wliich is 



