44 REPORT OF NEW JERSEY STATE MUSEUM. 



aaa. Body elongated, distinctly segmented except in certain parasitic forms; 

 carapace may extend over first thoracic segment ; thorax with four or 

 five pairs of biramous appendages in free forms ; abdomen limbless. 



COPEPODA 



■aaaa. Body imperfectly segmented, often of considerable size, and either 

 fixed or parasitic during adult life. CirripEdia 



Order PHYLLOPODA. 



The Phyllopods. 



Body small or microscopic in size, distinctly segmented and 

 ■covered by a cephalic carapace. The post-cephalic appendages 

 leaf -like. 



Key to the sub-orders, 

 a. Size moderate, with ten to sixty pairs of leaf-like swimteiing-feet. 



BRANCHIOPODA 



^a. Size minute, compressed body enclosed in bivalve carapace, swimming-feet 

 in four or five pairs, and large biramous antennae chief organs of loco- 

 motion. CLADOCERA 



Sub-Order BRANCHIOPODA. 



The Fairy Shrimps. 



Body usually, or in part, covered by large carapace. Mandibu- 

 lar segment greatly developed tergally, which in lower forms 

 bent down, forms two valves, joined by a true hinge which opens 

 and shuts by means of an adductor muscle, the shell thus re- 

 sembling those of certain bivalve fresh- water mollusca, such as 

 Cyclas and Pisidium. Antennae as two pairs. Mandibles paired. 

 Maxillae in two pairs. Some forms with a pair of maxillipedes. 

 Feet broad, leaf-like, with a series of six primary inner lobes 

 or endites and two exites, the latter forming a gill and accessory 

 gill or flabellum. Abdomen not clearly differentiated from 

 thorax, and abdominal feet not different in shape from thoracic 

 appendages. Body-segments vary in number from seventeen 



