328 Miss H. Richardson on the Isopods of the 



V. ONISCOIDEA. 

 Analytical Key to the Families of Oniscoidea. 



a. Flagellum of outer antennse not multiartlcu- 

 late. Buccal mass not very prominent 

 Lelow. First maxilte liave two plumose 

 setae on the inner plate. Mandibles with 

 molar expansion obsolete, without any 

 triturating surface, it being replaced by 

 brush-like recurved sette. Maxillipeds 

 with terminal part three-articulate ; epi- 

 gnath large, flanking the basal part. 

 Sexual appendage of male simple and 

 generally connected witli inner rami of 

 first pair of pleopoda. Uropoda with inner 

 branch smaller than outer and attached far 

 in front of it. 

 b. External antennte generally long, close 



together, with antennal openings large. 



Body scarcely able to be contracted into 



a ball. Head less manifestly immersed 



in first thoracic segment. Lateral parts 



of the head separated by a vertical mar- 

 ginal and inframarginal line. Clypeus 



arched. Legs generally long. Uropoda 



produced, reaching beyond the terminal 



segment of the abdomen and the post- 



terniinal segment. Terminal segment 



narrower than preceding ones and coni- 



cally produced at end XIIL Oniscid^. 



b'. External antennae generally short, with 



antennal openings small. Body able 



to be contracted into a ball. Head 



immersed in first thoracic segment. 



Lateral parts of the head undifferen- 

 tiated. Clypeus perpendicular. Legs 



generally short. Uropoda short, not 



reaching beyond the epimera of the 



terminal segment of the abdomen 



or the post-terminal segment. Terminal 



segment short and broad XIV. Abmadillidid-e. 



«'. Flagellum of outer antennoe multiarticulate. 

 Buccal mass prominent. First maxilUe 

 have three plumose setae on the inner 

 plate. Mandibles with molar expansion 

 large and broad, exhibiting a finely fluted 

 triturating surface. Maxillipeds with 

 temiinal part distinctly five-articulate ; 

 epignath short. External sexual ap- 

 pendages in male double. Inner ramus of 

 first pair of pleopoda of a similar struc- 

 ture in both sexes. Uropoda with both 

 branches styliform XV. Liqiid^e. 



