302 THE AMERICAN NATURALIST. [VoL. XXXIV. 
abdomen or the — segment. Terminal € short 
and broad . . Family XX. Armadillidide 
a’. Buccal mass Laine Fir irst Pos with three udis setz on the 
inner plate. Mandibles with molar expansion large and broad, exhib- - 
iting a finely fluted triturating surface. 
6. Head without any lateral lobes, frontal part rounded. Eyes well 
developed or wanting. Inner antennz with last joint very small, 
and without distinctly developed sensory filaments. Posterior 
maxillae with two thick hairy bristles. Maxillipeds with terminal 
part distinctly.five-articulate, masticatory lobe truncate at tip, 
epignath short. External sexual appendages in male double. 
Inner branches of first pair of pleopoda of a similar structure in 
both sexes, that of second pair in male terminating in a long 
stylet. Both branches of uropoda styliform. 
Family XXI. Ligiide 
&. Head with distinct, though not very large lateral lobes, front more 
or less produced. Eyes small or wanting. Inner antennz with 
last joint well dcmlüped and tipped with a number of delicate 
sensory filaments. Posterior maxille without any bristles. 
Maxillipeds with terminal part generally imperfectly articulated, 
masticatory lobe terminating in a thin lash, epignath narrow, 
linguiform. Sexual appendage of male simple; inner branch of 
both first and second pairs of pleopoda transformed for copulative 
purposes. Uropoda with branches conically tapered. 
Family XXII. Trichoniscidae 
' FAMILY XIX. ONISCID2. 
a. Flagellum of external antenna biarticulate. External opercular ramus 
of the first, second, and rarely of the third, or all the pairs of abdomi- 
nal appendages furnished with trachee. 
6. Abdomen abruptly narrower than thorax. Epimera of all the 
ominal segments small, subappressed. 
Metoponorthus Budde-Lund 
%. Abdomen not abruptly narrower than thorax. Epimera of all the 
abdominal segments large, prominent, well developed. 
c. Body very convex, capable of being rolled up into a perfect ball. 
Joints of the flagellum of the external antenne subequal. 
Last abdominal segment reaching very little beyond the 
epimera of the preceding segment. External branches of the 
uropoda equal in both sexes. External opercular branch of 
all the abdominal appendages furnished with trachez. 
Cylisticus Schnitzler 
c. Body more or less depressed, with lateral parts lamellarly ex- 
panded. Joints of the flagellum of the external antennze with 
