116 Illinois State Laboratory of Natu/ral History. 



Third segment and furca] rami about equal. Antennae 

 reaching base of abdomen. shoshone. 



9 (8). Terminal spines of inner ramus smooth, not nearly 



half as long as ramus, which is hairy at apex and on 

 inner margin. Second segment of outer ramus curved, 

 barely as long as preceding segment; armed at base 

 of third segment with an inconspicuous spine. Third 

 segment armed with two short spines but slightly longer 

 than the segment. Last thoracic segment armed with 

 small spines. First abdominal segment with a sharp 

 spine ; longer than remainder of abdomen. Antenna? 

 reaching furcal rami. novamexicanus. 



10 (2). Outer ramus 2-segmented. 



11 (12). Inner ramus almost rudimentary, not nearly reach- 



ing the middle of first segment of outer ramus. Second 

 segment of outer ramus considerably shorter than first ; 

 third segment represented by two spines, the inner 

 about twice as long as the outer. Last thoracic seg- 

 ment armed on each side with small spine. First 

 abdominal segment as long as remainder of abdomen ; 

 second segment very short ; third, longer than furcal 

 rami. Antennae reaching slightly beyond furca. 



minutus. 



12 (11). Inner ramus not rudimentary, reaching beyond the 



middle of first segment of outer ramus. 



13 (14). Second segment of outer ramus armed with a short 



spine ; denticulate within and without. Third segment 

 represented by two subequal spines. Inner ramus not 

 nearly reaching end of first segment of outer ramus ; 

 hairy on inner margin ; terminal spines fully half as 

 long as segment. First abdominal segment dilated, 

 about equal in length to remainder of abdomen ; sec- 

 ond segment and furcal rami each longer than third 

 segment. piscina. 



14 (IB). Second segment of outer ramus not armed with a 



spine. 



