420 A HISTORY OF RECENT CRUSTACEA 
CHAPTER XXVII 
TRIBE VII.—ONISCOIDEA 
Tuts tribe consists of the land Isopods, adapted for breath- 
ing air, but probably in all cases requiring that the air 
should be humid. In general uniformity and regularity 
of shape they are strikingly contrasted with the preceding 
parasitic tribe. The head is small, the seven segments of 
the pereeon are distinct, the pleon is narrower, and usually 
has six distinct seg ments, of which the sixth is the smallest. 
The first antenne never hove more than three joints, and 
may have fewer, or’ may be wholly wanting. The man- 
dibles are without ‘palp.’ The inner plate of the first 
maxille bears either two or three plumose sete. The 
second maxillz have two plates or only one. The maxilli- 
peds are occasionally seven-jointed, but seldom more than 
four-jointed. The seven pairs of trunk-feet are similar to 
one another; the hinder more or less exceeding in length 
those that precede ; all are gressorial. The pleopods are 
branchial. Of the five pairs rarely the first is obsolete ; 
the second and sometimes also the first have sexual organs 
in the male. The uropods are of variable character, never 
powerful organs; their branches are single-jointed. Five 
families are included in the tribe, the Ligiidee, Tylidze, 
Helleriidee, Oniscidx, and Armadillidide. 
Family 1.—Ingude. 
The pleon consists of six segments, of which the first 
two are narrower than the third. The first antennz are 
small, three-jointed. ‘The first maxille have three sete 
on the inner plate. The second maxille have two plates. 
2" = 
—_— ee 
