214 THE AMERICAN NATURALIST. [Vor. XXXIV. 
the inner upper margin and apex never setose, 
the apex and sometimes the inner upper margin, 
at least in the males and females without eggs, 
being furnished with outward curved hooks 
f. Mandibles with the secondary plate very often 
visible ; palp with no inflated joint. Maxil- 
lipeds commonly seven-jointed, sometimes 
four-jointed, the last joint in the latter case 
rather short, obtuse. Antenna long, un- 
Rond with well-defined peduncle and fla- 
ge . Family VIII. Ægidæ 
F: seandtbiee with no is wna plate ; the palp 
in adults with first joint or both first and 
second joints inflated. Maxillipeds always 
four-jointed, last joint rather long and 
narrow, subacute. Antenna much reduced 
without clear distinction between peduncle 
and flagellum. Family IX. Cymothoide 
ad’. Uropoda with one of the branches almost obsolete or 
rudimentary — not lamelliform. 
Family X. Limnoriide 
€. Abdomen consisting of less than six segments. 
d. n with two segments. Uropoda with one 
branch fixed, immovable. Family XI. Sphæromidæ 
d'. Abdomen with four segments. Uropoda with both 
branches movable. . . . Family XII. Serolide 
FAMiLY III. GNATHIID4E. 
Genus Gnathia Leach. z 
a. Mandibles in male with the basal part ornamented on the superior margin 
with an elevated crest, which is irregularly dentate. Legs furnished 
with many spiny processes. Gnathia cristata (Hansen), JV, 116 fms. 
a’. Mandibles in male without elevated crest on the superior margin. Legs 
without spiny processe: 
à. Mandibles in ok with slight notch outside, inner edge obtusely 
produced in the middle, tip acute, slightly incurved. Front of 
head not vite in the middle beyond the antero-lateral 
angles. . Gnathia elongata (Krøyer), W 
&. Mandibles in ‘mals carinate on outer side near the middle, the 
carina ending in a tooth-like process, irregularly and bluntly 
toothed near the base within, turned upward at apex. Front 
of head produced in the middle much beyond the antero-lateral 
angles. 
Gnathia cerina (Stimpson), W, 10-220 fms. (See Fig. 2, p. 211-) 
