( 19) 



C stj/(jius, Bund)/, nostrum 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. 



C. placidtts, 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. vlrilis, 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. wisconsinensls. Bund//. Rostrum nearly flat above, narrowed in 

 front ; antennal plates longer than rostrum ; maxillipeds hairy within and 

 below at base, 



FAMILY PALAExMONIDAE. 



Abdomen compressed. Carapace without transverse channel, its lower 

 edgss 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. ohonh, 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 111). 



Genus Palaemonetes . 



Diflfers from Palaemon by the absence of mandibular palpi 



