THE CUMIDA 30] 
Definition of the sub-order Cumacet. 
The carapace covers the segments of the head and all 
but the last five segments of the trunk. The antero-lateral 
lobes are drawn towards one another usually in advance of 
the frontal region. The first maxillipeds carry a respira- 
tory organ of which the hinder division almost always is 
furnished with branchial sacs, and the front division forms 
an exserted tube during respiration for the outflow of 
water from the branchie. Of the pereeopods at fewest the 
first pair have exopods. Of the pleon-segments the fifth 
is the longest. The appendages of the sixth are the only 
pair of uropods. 
The eight families included are the Cumide, Vaun- 
thompsoniide, Leuconide, Nannastacidee, Campylaspide, 
Pseudocumidz, Lampropide, Diastylidee. 
The peculiarity of the fifth pleon-segment being the 
longest is reproduced in the curious Isopod genus Phrea- 
toicus, Chilton, which is otherwise nearer the Amphipoda. 
Family 1.—Cumide. 
The first antennz are very small, with one of the 
flagella rudimentary; the second antenne in the male 
have the filiform flagellum composed of many short joints. 
The mandibles have the anterior branch produced and 
armed with a dense lateral series of spines. The epipod 
of the first mavxillipeds is very large, with the branchial 
sacs numerous, leaf-like, in a straight series. The third 
maxillipeds have some of the joints expanded and laminar. 
Only the first pair of perzeopods in either sex have well- 
developed exopods. The male has five pairs of pleopods 
well developed. The inner branch of the uropods is one- 
or two-jointed; the telson is wanting. Five genera are 
included in this family. 
Cuma, Milne-Edwards, 1828, has the carapace mode- 
rately developed, only four segments of the trunk 
distinct behind it; the eye well developed; the 
third maxillipeds with the second joint apically 
