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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 preceding
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;