CLASS vermes: order merostomata. 



236 



ORDER MEROSTOMATA. 



General Characteristics. — The Merostomata (thigh- 

 mouths) have the limbs placed around the mouth and use 

 the basal joints for jaws, whence the name of the order. 



Limulidae. — Limulus, the Horse-shoe Crab,* is the only 



Mg. im. 



Fig. MS. 



LirrMus moaiicSnus, Horse-shoe Crab. A- 



Umter Surface of Limulus. 



genus now living. When moulting, the shell splits along the 

 anterior border and not down the back as in other Crustacea. 



CLASS III. VERMES. 



General Characteristics.— The Vermes (worms) are 

 articulated animals without jointed limbs, their place being 

 supplied in some by bristles. The blood is generally red and 



* The Trilobites. which fifnire bo largely in Palaeozoic Geology, were nearly- 

 related to the Horse-shoe Crab. (Figs. 402, 403.) 



