CLASSIFICATION. 17 



Copepoda, the Epizoa, the Branchiopoda, the Ostracoda, 

 and the Pectostraca. 



" The Copepoda. — In these Entomostraca, which 

 come nearest to the Eurypteridce, the cephalic shield, 

 which is discoidal and not folded longitudinally, is 

 succeeded by a certain number of free thoracic and 

 abdominal somites. The antennules and antennae are 

 large, and, as in the Eurypteridce, are organs of loco- 

 motion and sometimes of prehension. The anterior 

 thoracic members are converted into foot-jaws ; the 

 posterior serve as paddles, the limbs of each pair 

 being often united together in the median line, as in 

 Limulas. The embryo leaves the egg as a Nauplius" 



