THE CANADIAN ENTOMOLOGIST. 87 



tion. Setye brown, with yellowish bases, very short and abruptly 

 tapering. 



Type — A single female from Reno, Nevada, in the Museum of 

 Comparative Zoology. 



Peltoperla thyra, n. sp. 



Length of male IS mm.; expands 30 mm. 



Colour yellowish l)rown. Head obscure, but a little darker 

 around the ocelli. Prothorax nearly uniform yellowish brown, 

 faintly rugose, somewhat more squarely angled than in the other 

 species, though like the others narrowed posteriorly and some- 

 what rounded behind. Legs yellow, with tips of tibiae and tarsi 

 darker. Wings yellowish-hyaline; veins amber-brown: abdomen 

 yellowish, with the apical segments much darker, Seta^ yellowish 

 basally, darker towards the apex. 



The 9th ventral segment is divided by a U-shaped suture, 

 which separates off the upturned posterior lobe from the basal 

 part of the segment, and jUst before the suture on the mid-ventral 

 line there is a broad, chitinous callosity that is very different from 

 the knob of the males of the other two species above described. 

 It is not elevated upon a stalk, but merely caps the mid-ventral 

 portion of the hind margin of this basal half of the sternum of the 

 9th segment. On the dorsal side the 9th segment is broadly 

 excavated on its hind margin, a wide V-shaped notch almost 

 dividing it in two in tlie median line. The edges of the V are up- 

 turned and chitinized. The 10th segment is not visible externally, 

 reduced to a very narrow, thinly chitinized ring that is somewhat 

 wider below. Supra-anal plate remarkably developed, broadened 

 upward, and then recurved forward at its tip, knobbed at the end 

 and bearing two thinner, wing-like appendages at its sides. The 

 median terminal knob is beset with backwardly curved prickles. 



The ventral callosity of the 9th segment is crescentic in outline 

 when \iewed from below. Within the apex of the 9th segment 

 there are visible a pair of chitinized appendages, the nature of 

 which is unknown. They are divergent basally, parallel and 

 approximate at their tips, and possibly are in the nature of copula- 

 tory organs. 



Type — Single male specimen from Nevada in the Cornell 

 University collection. 



