No. 400.] JVORTH-AMERICAN INVERTEBRATES. 301 
oblong-oval. Mandibles without any molar expansion; cutting 
S 
structure, though somewhat different in size; two succeeding 
pairs elongated. Dactylus wanting on natatory legs. Uropoda 
simple, biarticulate . . . . . Munnopsis M. Sars 
/. Body, with anterior division less skarpy marked off from posterior ; 
three posterior segments very large and broad. Caudal segment 
semioval. Mandibles with molar expansion ; cutting edge divided 
into strong teeth. First pair of legs shorter than three succeed- 
ing pairs, which are subequal in length, and very much elongated. 
Dactylus distinct on natatory legs. Uropoda biramous, branches 
Single-jointed . . . . Eurycope G. O. Sars 
a’. Head very large and bend. iaae truncated in front, lateral 
parts greatly expanded. First four thoracic segments slightly exca- 
vated transversely. Superior antennæ, with flagellum not much 
elongated. First two pairs of natatory legs of similar structure, 
carpal joint large and expanded, cordiform ; last pair much narrower 
than two succeeding pairs, carpal joint but slightly expanded. a 
segment triangular in form . . . + Ilyarachna G. O. 
Genus Munnopsis M. Sars . Wiede bos M. Sars, V, 20-122 ws 
Genus Eurycope G. O. Sars. 
Eurycope ioris G. O. Sars, N, 119—220 fms. 
Genus Ilyarachna G. O. Sars 
PNR hirticeps G. O. Sars, JV, 100-227 fms. 
V. ONISCOIDEA (Terrestrial Isopoda). 
a. Buccal mass not very prominent below. First maxillæ, with two plu- 
mose setæ on the inner plate. Mandibles with molar expansion 
obsolete, e vd triturating surface, it being replaced by brush- 
like recurved se 
6. External d generally long, close together, with antennal 
openings large. Body, as a rule, scarcely able to be contracted 
into a ball. Head less sanfte immersed in first thoracic seg- 
ment. Lateral parts of the head separated by a vertical mar- 
ginal and infra-marginal line. Clypeus arched. Legs generally 
long. Uropoda produced, reaching beyond the terminal segment 
of the abdomen and the preceding segment. Terminal segment 
narrower than preceding ones and — produced at end. 
amily XIX. Oniscide 
6’, External antennz generally short, with lae openings small. 
Body able to be contracted into a ball. Head immersed in first 
thoracic segment. Lateral parts of the head undifferentiated. 
Clypeus perpendicular. Legs generally short. Uropoda short, 
flattened, not reaching beyond the terminal segment of the 
