.54 THOMAS SAY FOUNDATION 



The prothorax is brown-bordered except for a yellow 

 spot on the middle at the front and another at the rear. 

 These spots are connected by the usual pale line, which 

 in this species is rather narrow and obscure. Embossed 

 markings at sides of the disc rather coarse. The pro- 

 thorax in shape is quadrangular, little wider than long 

 and scarcely narrower to rearward. Legs yellowish with a 

 wash of pale brownish on both ends of the femora (ex- 

 cept at knees) and tibiae and tarsi externally. Wings 

 smoky hyaline with the veins brown, the basal ones a little 

 inf uscated. Abdomen brown above, paler beneath ; tails 

 yellowish with rings of brown on apices of the segments. 



Male. Abdominal segments normal as far as the ninth 

 which is moderately elongated beneath, being twice as 

 long on the ventral as on the dorsal side, its sternum 

 scarcely prolonged into a genital scoop that is set off at 

 each side by a very shallow notch or fold. On the dorsal 

 side there is a narrow, strongly chitinized tranverse ridge 

 across the declined and sloping apex of the tergum. The 

 tenth segment is cleft longitudinally on the dorsum to 

 accommodate a large U-shaped retractile supra-anal proc- 

 ess (invisible except on dissection), and the upper end 

 of each half is emarginate in the middle, rounded on the 

 proximal angle, while the distal superior angle is produced 

 into a short, sharp, thorn-like spine. The two spines are 

 directed somewhat forward, and constitute incipient 

 genital hooks. 



Female. The subgenital plate is prolonged backward 

 into a single broadly rounded lobe, reaching halfway 

 across the sternum of the ninth segment. 



Distribution. — Canadian Rockies ; Selkirk Mountains, B. 

 C, J. C. Bradley. Kaslo, B. C, June 2, H. G. Dyar. 



Perlodes tibialis Banks. 



lit 14. Perlodes tibialis Banks, Proe. Ac. Nat. Sci., Phila., p. 608. 



Male. Length to tip of wing 25 mm. ; expanse 40 mm. 



We have not had for dissection any specimens that 

 seem referable to this species, but the junior author has 

 had the privilege of examining the type (a male) in the 

 Museum of Comparative Zoology at Cambridge, Mass., 

 and it seems to differ from the preceding species by the 

 following characters: 



1. It is larger in size, 40 mm. in expanse of wing as 

 compared with 32 mm. in .P. bradleyi. 



