C. stygius , Bundy. Rostrum long, triangular, with small apical teeth ; 
outer margin of finger hairy ; first abdominal legs recurved at tip and three- 
toothed. 
bb 
First abdominal legs of male distinctly bifid. 
c 
C. obesus, Hagen. First abdominal legs short, thick, branches stout, 
tips recurved, obtuse. Areola linear. 
cc 
First abdominal legs of male with branches usually long and slender. 
d 
C. immunis , Hagen. Both branches gradually, strongly and equally 
recurved. Rostrum short and conical. 
dd 
Branches not strongly and equally recurved. 
e 
C. propinquus, Girard. Rostrum carinated (7) on middle of anterior 
half. 
ee 
Rostrum not carinated. 
G. placidus , Hagen. Rostrum excavated, margins thickened ; maxilli- 
peds not hairy beneath ; greatest width of hand contained about three times 
in length of outer margin, inner edge of outer finger not bearded, forearm 
without two rows of distinct spines beneath. 
C. virilis, Hagen. Rostrum sub-excavated, margins thickened, hardly 
converging; antennal plates not longer than rostrum; maxillipeds bearded 
without, beneath and within ; greatest width of hand about two and one- 
third times in length of outer margin, outer finger bearded within, forearm 
with two rows of distinct spines beneath. 
C. wisconsinensis, Bundy. Rostrum nearly flat above, narrowed in 
front ; antennal plates longer than rostrum ; maxillipeds hairy within and 
below at base. 
FAMILY PALAEMONIDAE. 
* 
Abdomen compressed. Carapace without transverse channel, its lower 
edges free throughout. Gills composed of plates. The third pair of feet 
never chelate. 
Genus Palaemon. 
Rostrum long, compressed, serrate; two inner antennae with flagella (8), 
mandibles (9) with three-jointed palpus (10), first pair of legs slender, second 
stronger, both chelate. 
P. ohonis , Smith Rostrum slightly curved upward at tip, about 
twelve teeth above and three to five below. Hand of second pair of legs 
about once and a half the length of the carpus (11). 
Genus Palaemonetes. 
Differs from Palaemon by the absence of mandibular palpi. 
