176 PROCEEDINGS OF THE ACADEMY OF [1895. 



G. O. Sars creates for some species the genus Sclerocrangon. I 

 can not adopt this genus, but I retain it as a subgenus. 



a 1 . Carapace strongly sculptured, at least two spines in the median 

 line. Abdomen mostly strongly sculptured, seldom nearly smooth. 



• Subgenus: Sclerocrangon. 



b t . Median keel of carapace with three or four spines. Lateral 

 keels of carapace partly granulate or rugose. Abdomen sculp- 

 tured by longitudinal keels and transverse furrows. 

 c x . Epimera of the abdominal segments provided with spines. 

 Carapace with more than three keels. Spines not excessively 

 developed. Sternum with a sharply serrated keel. 

 d x . Keels of the carapace sharply granulated, keels of the ab- 

 domen sharp, epimera of the abdominal segments with 

 one to three spines. 



e x . The rostrum is simple Cr. salcbrosus (l) 7 . 



e 2 . A long acute tooth is given off from the lower side of ros- 

 trum, which reaches as far forward as the tip of the ros- 

 trum Or. atrox. 



d... Keels of the carapace somewhat rugose, keels of the abdo- 

 men not sharp, epimera of the abdominal segments only with 



one spine each Or. boreas (14). 



c 2 . Epimera of the abdominal segments without spines. Cara- 

 pace with three keels, the median one with four very long 



spines. Sternum with a dentated keel Cr. sharpi (2). 



6 2 . Median keel of carapace with two spines. Lateral keels of 

 carapace smooth, ending in front in the usual spines. Abdomen 

 smooth, or with smooth longitudinal keels. 

 Cj. Epimera of the first and second abdominal segments with 

 small spinules. Abdomen with longitudinal keels. Often a 

 rudimentary third median spine in the median line of carapace 

 between the two well-developed ones. 



Cr. agassizi. 



Cr. procax. 



c 2 . Epimera of abdomen without spinules. Median spines of 

 carapace small. 

 d x . Abdomen with longitudinal median keels. 

 e x . Sixth abdominal segment with two sharp keels. 



Or. intermedins (2). 



e 2 . Keel of the sixth abdominal segment behind the middle 



finely furrowed Cr. angusticauda (4) . 



(/,. Abdomen not sculptured Cr. munitus. 



a.,. Carapace not sculptured, only with one median, and mostly with 

 one lateral spine on each side (the latter being absent in Cr. capen- 

 sis). Abdomen nearly smooth Subgenus: Crangon. 



7 I put in parentheses, following each species, the number of specimens 1 

 have examined myself. 



