CLASS VEEMES: ORDER MEROSTOMATA. 



235 



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. 



Fig. W3. 



Limulus mollucclnus, Horse-shoe Crab. 



Under 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 figure so largely in Palaeozoic Geology, were nearly 

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



