58 RATHBUN 



E. Rostrum less than twice as long as the eye washingtoniana. 

 E 7 . Rostrum twice or more than twice as long as the eye. 

 F. Antennular scale shorter than first segment of peduncle 



vicwa. 



F 7 . Antennular scale longer than first segment of peduncle. 

 G. Fifth segment of abdomen not armed with a spine on 



either side affinis. 



G 7 . Fifth segment of abdomen armed with a spine on 



either side. 

 H. Rostrum longer than the rest of the carapace 



unalaskensis. 

 H 7 . Rostrum no longer than the rest of the carapace 



Polaris. 

 A'. No supraorbital spine or spines. 



B. Rostrum about as long as or longer than the rest of the carapace. 

 C. Third, fourth, and fifth segments of abdomen carinated, the carina 

 on each segment terminating in a sharp spine . . barbata. 

 C'. Third, fourth, and fifth segments not all carinated nor ending in 



a sharp spine. 



D. Terminal half (at least) of rostrum devoid of spines above. 

 E. Third abdominal segment with an angle or hump, in profile, 



toward the posterior end. 



F. More than 3 dorsal teeth, one or more in front of eyes. 

 G. Sixth abdominal segment less than twice as long as 

 wide. Rostrum deep, one fourth as deep as long 



carinata. 

 G'. Sixth abdominal segment more than twice as long as 



wide. Rostrum more slender. 



H. Maxilliped with epipod. Scale at base of antennula 

 extending beyond first segment .... fitxa. 

 H 7 . Maxilliped without epipod. Scale at base of an- 

 tennula not reaching beyond, or only slightly 



beyond, first segment gracilis. 



F'. Three dorsal teeth, none in front of eyes . . tridens. 

 E 7 . Third abdominal segment smoothly rounded, without angle 



or hump. 

 F. One or more superior rostral spines in front of eyes. 



G. No pterygostomian spine stylus. 



G 7 . A pterygostomian spine amabilis. 



F 7 . No superior rostral spine in front of eye . . fabricii. 

 D'. Terminal half of rostrum with spines (in part at least). 

 E. Terminal third of rostrum unarmed above and below 



biunguis. 

 E 7 . Terminal third of rostrum not entirely unarmed. 



F. Sixth abdominal segment longer than seventh . decora. 

 F 7 . Sixth abdominal segment shorter than seventh. 

 G. Maxilliped exceeding acicle. 



H. Rostrum straight above. Epipods on maxillipeds 

 and first two thoracic feet .... paludicola. 



