2 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



D. Sides of head emarginate and produced laterally beyond 



the eyes, which are dorsal Chiridotea p 215 



DD. Sides of head not produced laterally; eyes placed 



laterally. 

 E. Flagellum of second antennae multiarticulate. 



Idothea p. 218 

 EE. Flagellum of second antennae not multiarticulate. 



F. Second pair of antennae shorter than first. .Edotea p. 223 

 FF. Second pair of antennse longer than first 



Erichsonella p. 227 

 BB. Uropods terminal. 



C. Pleopods exclusively branchial. 



D. Fresh-water. First pleopods in male not coupled with 

 second pair, peduncle short; second pair small and 



situated below first pair Asellus p. 231 



DD. Marine. First pleopods in male coupled with second 

 pair, peduncle elongate; second pair large and situated 



external to first Jaera p. 233 



CC. Pleopods fitted for air-breathing. 



D. Second antennae long and close together; legs long; uro- 

 pods produced, reaching beyond terminal segment of 

 abdomen. 

 E. Flagellum of second antennse of three joints. 



F. Epimera of thoracic segments large, with posterior 

 angles acute; abdomen not abruptly narrower 



than thorax Oniscus p. 238 



FF. Epimera of thoracic segments small; abdomen ab- 

 ruptly narrower than thorax Philoscia p; 240 



EE. Flagellum of second antennae of two joints. 



F. Abdomen not abruptly narrower than thorax; epi- 



mera of abdominal segments large. 

 G. Body very convex, capable of rolling up like a ball; 

 joints of flagellum of second antennae sub- 

 equal Cylisticus p. 241 



GG. Body more depressed, scarcely contractile; 

 first joint of flagellum of second antennae 



longer than second Porcellio p. 243 



FF. Abdomen abruptly narrower than thorax; epimera 



of abdominal segments small. . Metoponorthus p. 247 

 EEE. Flagellum of second antennae of four joints. 



Actoniscus p. 249 



DD. Second antennse generally short. Contractile into 

 ball; head deeply immersed in first thoracic segment. 



Armadillidium p. 251 



