62 THOMAS SAY FOUNDATION 



at its bottom. Segment 10 is cleft above for the reception 

 of the retractile U-shaped supra-anal process, and the 

 rear angle beside the cleft each side is prolonged into a 

 finger-like lobe that is bent forward to form a genital 

 hook. The U-shaped supra-anal process is slightly con- 

 stricted below an ovoid summit, and its stylets have sharp 

 thorn-like tips. 



Female. Subgenital plate broad, set off at sides by 

 folds evenly truncate across its wide apex and more 

 strongly chitinized on its lateral angles. The appearance 

 of this plate is exceedingly variable in pinned specimens, 

 since the middle portion of the hind margin is thin and 

 may be variously in- or out-rolled in drying. It is nearly 

 always more strongly chitinized at the sides next to the 

 marginal folds. 



Distribution. — Colorado ; Boulder, Colo., Apr. 4 and 

 Apr. 6, 1904 (S. A. Rohwer) ; "Fallen Log," June 19, 1916 

 (A. C. Browne) ; Logan, Utah, Apr. 30, 2 females and 2 

 brachypterous males; Tenas L., B. C, Apr. 1904; Fair 

 Oaks, Calif., May 10, 1918; Lewis Lake, B. C, May, 1904; 

 (Stanford University Collection) ; Bozeman, Mont., May 

 10 (R. A. Cooley). 



Perlodes aurea Smith. 



(Plate 7, fig. 23.) 

 1917. Arcynopteryx aurea Smith, Trans. Amer. Ent. Soc, 43:477. 



We have nothing to add to the original careful descrip- 

 tion, which is copied herewith : 



Female. Length to tip of wings, 21 mm. ; expanse of 

 wings, 32 mm. 



This species is apparently rather closely related to 

 Arcynopteryx vagans. 



Color: It is yellowish-brown with yellow markings. 

 Head triangular, three small ocelli arranged in an isos- 

 celes triangle the base of which is greater than the sides, 

 the distance from the inner margin of the eyes to the pos- 

 terior ocelli less than the distance between the posterior 

 ocelli, but greater than that from them to the anterior 

 ocellus. Outside the ocellar triangle, conspicuous, dark 

 brown tubercles situated a little nearer the paired ocelli 

 than the inner margin of the eyes. M-shaped mark prom- 

 inent. The anterior region of the head uniform yellow- 

 ish brown, the occiput with three pale yellow spots, a 

 small median triangular one with larger oval ones on 

 either side. Under side of head pale, palpi brown. 



