170 



broad and laminar, though scarcely expanded distally, terminal part poorly deve- 

 loped and never composed of more than 3 joints, the last very narrow; mastica- 

 tory lobe short, truncate at the tip; epignath large, flanking the basal part. 

 Legs, as a rule, slender, increasing in length posteriorly. Sexual appendage of 

 male simple, conic, and generally connected with the inner rami of the 1st pair 

 of pleopoda; the latter very largely developed, terminating each in a highly chiti- 

 nized, conical joint obliquely grooved below, for conducting the evacuated sperm. 

 Inner ramus of 2nd pair of pleopoda in male terminating in a slender lash finely 

 pointed at the tip. Uropoda with the outer ramus more or less flattened, lanceo- 

 late, inner much smaller, sublinear, and, as a rule, attached far in front of the outer. 

 Remarks. This family belongs to the 2nd section of the Oniscoida, and 

 comprises by far the greater bulk of the tribe, for which reason it might perhaps 

 be convenient to subdivide it into several families. The northern forms, however, 

 belonging to this group exhibit in reality a very close relation to each other, 

 the structure of the oral parts being especially very uniform in the different genera, 

 whereas these appendages exhibit well-marked differences from those in the 2 pre- 

 ceding families. For instance, in the mandibles of all the forms with which I am 

 acquainted, a true molar expansion, is wanting, and instead of it there is a peculiar 

 recurved brush-like appendage somewhat resembling a strong seta. Moreover the 

 inner masticatory lobe of the anterior maxillse in all the forms has but 2 hairy 

 setse at the tip, and is very much narrower than the outer. Finally, the ter- 

 minal part of the maxillipeds is very much reduced, and never consists of more 

 than 3 joints. The conically produced last segment of the metasome affords an- 

 other characteristic feature common to all the forms, and the structure of the 

 uropoda is also characteristic from the insertion of the inner ramus far in front 

 of the outer. Contrary to what is the case in the Trichoniscidce, the struc- 

 ture of the copulative appendages in the male exhibits a remarkable uniformity 

 throughout this family. About 20 different genera have been referred to this 

 family, 5 of which will be treated of below. 



den. 1. OnlSCUS, Linne, 1767. 



Generic Characters. Body broad and depressed, with the lateral parts 

 of the segments lamellarly expanded. Cephalon with well defined lateral lobes, 

 front imperfectly defined from the epistome. Metasome not abruptly contracted; 



