PLECOPTEBA OF NORTH AMERICA 45 



dark mark above ; tibia with a dark mark at the proximal 

 end ; tarsi darker toward the tip. 



Abdomen dark brown. Tails yellowish at base, darker 

 toward tip, basal segments short; segments beyond the 

 middle at least five times as long as wide. 



Male. First segment of the abdomen above with a pale 

 whitish spot on each side. The dorso-lateral posterior mar- 

 gins of segments two to nine with yellow rounded knobs, 

 the size of the knobs gradually increasing posteriorly, and 

 those on segment 6 to 9 quite hairy. Dorsal posterior 

 border of segment 9 emarginate, the area between the 

 knobs hollowed out scoop-like with an anteriorly produced 

 heavily chitinized raised triangular projection. The en- 

 tire hollowed area thickly covered with very short spines. 

 The lateral posterior margin of segment nine straight, 

 hind ventral margin rounded; the ventral portion of this 

 segment is divided from the lateral areas by diagonal 

 carinae. Segment ten and supra-anal process entirely 

 covered by segment nine. Subanal plates yellowish, dark- 

 er brown at the pointed end where bent upward and pro- 

 jecting forward, the tips a little outcurved and reaching 

 a little beyond the posterior border of segment nine. 



Female. The middle area of the eighth ventral seg- 

 ment black and a dark triangular mark on the postero- 

 lateral angle, followed by similar paired marks on seg- 

 ment nine. The subgenital plate (chitinized middle por- 

 tion of the eighth abdominal sternite) bears a small, dis- 

 tinct, acute notch on its hind margin, the latter being M- 

 shaped. There are narrow blackish lines across the ex- 

 treme apical ventral margin of some of the preceding seg- 

 ments. 



Distribution. — Truckee, Nev. ; Olympia, Wash., $ and 

 5 ; Seattle, Wash. ; Seven Mile Hill, Ore. ; Wallowa 

 Mts., Baker Co., Ore. July 4 (E. P. Van Duzee). We 

 have seen no specimens from the Rocky Mountains that 

 indubitably belong to this species ; and we fear that 

 earlier distribution records rest on incorrect determina- 

 tions, growing out of the circumstance that males of the 

 two original species described by Hagen have not hitherto 

 been certainly known. Excellent specimens of both sexes 

 of this species were received from Trevor Kincaid col- 

 lected at Olympia, Wash., and the females agree well with 

 Hagen's type (examined by both of us), and these Wash- 

 ington specimens we have made the basis of our descrip- 

 tion. 



