220 REPORT OF NEW JERSEY STATE MUSEUM. 

 Key to the super-families. 



a. Legs of first pair not cheliform. 

 b. Urpoda terminal. 



c. Pleopoda fitted for air-breathing. oniscoidea. 



cc. Pleopoda not fitted for air-breathing, entirely branchial. 



/. Pleopoda generally covered by thin opercular plate (modified 

 first pair) ; free-swimming. aselLOIDe.x. 



ff. Pleopoda never covered by opercular plate : parasitic. 



BOPYROIDEA. 



hb. Uropoda lateral. 



g. Uropoda valve-like, inflexed, arching over pleopoda, latter 



largely branchial. idotheoidea. 



gg. Uropoda form together with terminal segment of abdomen 



caudal fan ; pleopoda for most part natatory, cymothoidea. 



aa. Legs of first pair cheliform ; uropoda terminal ; pleopoda, when distinct, 



exclusively natatory. Tanaioidea. 



Super-Family ONISCOIDEA. 



Tlie ]Vood Lice. 



Body more or less depressed, oval or oblong in form, and 

 sometimes capable of being rolled into a ball. Cephalon gen- 

 erally small, more or less sunk into first segment of mesosome, 

 showing no true rostral projection, and lateral parts may be 

 more or less expanded. Mesosome formed of seven well-defined 

 and rather uniform segments, with their lateral parts generally 

 expanded to thin fornicate plates. Metasome usually divided 

 into six well-defined segments, lateral plates or epimerae, of 

 which some may be expanded similarly to those of mesosome. 

 Usually this not the case with the last, and two anterior seg- 

 ments, which are also usually smaller than three middle ones. 

 First pair of antennae always very small, placed inside second 

 pair, never with more than three joints, and last of which often 

 rudimentary. Second pair of antennae normal, formed by a 

 five-articulated peduncle and a flagellum generally divided into 

 a restricted number of articulations. Length of second antennae 

 moderate, seldom more than half of l3ody length. Buccal mass 

 more or less prominent, and oral parts adapted to biting and 



