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 swimtning-feet. 



BRANCHIOPODA 



aa. 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 Pisidiuin. 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 



