I80PODS OF NORTH AMERICA. 499 



e. Sixth abdominal segment in male with post-lateral angles produced in 



long processes Genus Cryplione Hansen 



e' '. Sixth abdominal segment in male with post-lateral angles not produced 



in long processes Genus Pseudione Kossmann 



c' '. Lateral parts or pleural lamellae of abdomen of female rudimentary or absent. 

 d. Pleopods present in female. 

 e. Some or all of pleopoda in female tri-ramous. 



/. All the pleopoda in female tri-ramous. Sixth segment of thorax greatly 

 longer than any of others. Uropoda in female oval, with a small 



conical process between them Genus Stegophryxus Thompson 



/'. First three pairs of pleopods tri-ramous; last two pairs bi-ramous. 

 Sixth segment of the thorax not greatly longer than any of the 

 others. Uropoda elongated, with no process between them. 



Genus Stegias Richardson 

 e' '. None of pleopoda tri-ramous in female. 

 /. Pleopoda bi-ramous in female. 

 g. Uropoda present in female. 



h. Uropoda bi-ramous in female Genus Batkygyge Hansen 



h' '. Uropoda simple, single-branched in female. 

 i. Both branches of pleopoda in adult female similar in size and 

 shape, narrow, elongated. Male with segments of abdomen 

 distinct and with a pair of elongated appendages to each of 

 the first five segments. Uropoda present in male, single- 

 branched. First abdominal segment in both sexes furnished 



with two dorsal papillae Genus Phyllodurus Stimpson 



i' '. Branches of pleopoda in adult female unlike; outer branch 

 narrow, elongated; inner branch oval, small. Male with seg- 

 ments of abdomen fused and without any appendages to the 

 abdomen; without uropoda. First abdominal segment in both 

 sexes not furnished with two dorsal papillae. 

 j. Posterior lobe of lateral margins of all the segments of the 

 thorax more or less produced into processes. Abdomen of 

 male narrow, tapering, not furnished with dorsal tubercle. 



Genus Argeia Dana 



j f . Posterior lobe of lateral margins of thoracic segments not pro- 

 duced into processes. Abdomen of male large, rounded, 

 and furnished with a prominent median dorsal tubercle 



near the base Genus Parargeia Hansen 



g'. Uropoda wanting in female. 



h. Segments of abdomen fused in male. Segments of abdomen dis- 

 tinct in female Genus Probopyrus Giard and Bonnier 



//. First three segments of abdomen distinct in male; last three seg- 

 ments fused. First four segments of abdomen distinct in female; 



last two segments fused Genus Bopyriscus, new genus 



/'. Pleopoda simple, single-branched in female. 



Genus Bopyrina Kossmann. 

 d'. Pleopoda wanting in female Genus Bopyroides Stimpson 



81. Genus PHRYXUS Rathke. 



Abdominal parasites. 



Body of female very asymmetrical, one side being very much larger 

 than the other. 



See Sars for characters of genus, Crust, of Norway, II, 1899, pp. 214-215. 



