72 THE CANADIAN ENTOMOLOGIST. 



than at base. Apex of lo nearly equal to base of 9. Ventro-lateral mar- 

 gins of 8, 9 and 10 and ventral surfaces of 9 and 10 yellowish, vulvar 

 lamina rather longer than depth of 8 at apex, spout-shaped, elongate tri- 

 angular in profile, with ventral surface slightly concave, apex rounded. 



Appendages )^ longer than 9+10, black, evenly covered with short 

 hairs, slender, subcylindrical, slightly bent inwards in proximal half, en- 

 larging distally its proximal two-thirds, thence narrowing again very 

 slightly, apex rounded. A slight carina runs along outer ventro-lateral 

 margin in its proximal half 



Wings {S 9) hyaline, yellow at base in ? , becoming somewhat 

 suffused with brownish in old examples, venation black, pterostigma dark 

 brown. 



Front-wings : Antecubitals 7-8, postcubitals 5-9, usually 7 ; triangles 

 2-ceIled, internal triangles 3-celled, one submedian cross-vein on a level 

 with the first antecubital ; 3 post-triangular cells, followed by 2 rows of 

 cells to near the level of separation of the median and principal sectors, 

 then 3 rows ; generally 4-5 cells at the margin : membranula sooty-gray. 



Hind-wings : Antecubitals commonly 5, sometimes 6, postcubitals 

 6-10, generally 7-9; triangles 2-celled, internal triangles free, one other 

 submedian cross vein before the level of the first antecubital ; 3 post- 

 triangular cells ( I ? has 2 on one side, 4 on the other) followed by 2 very 

 short rows of cells, then 3 rows which divide and subdivide until at the 

 margin there are 9-12 cells; anal triangle of S 2-celled; membranula 

 sooty-gray, paler towards base, the pale area usually confined to a small 

 spot at the immediate base, but sometimes diffused over the basal half. 



Dimensmis : Abdomen (incl. apps.) $ 41-45, 9 45.5-46 ; sup. 

 apps. i 4, apps. 9 4-5-5-25 ; hind-wing ^ 37-40, ? 39-40; ptero- 

 stigma 2.6-3; hind femur $ 8.5-9, ? 8-8.5 mm. 



This species is most nearly related to S. elongata (Scudd.), from which 

 It differs chiefly in the superior appendages of the male. In elongata 

 these appear, when viewed from above, slenderer, straighter and more 

 regular in outline. The proximal half is slightly bent inwards, but in the 

 distal half they are parallel, with the apices well separated. The basal 

 tooth is much smaller than in Wmia)?i5oni,a.r\d invisible from above, while 

 there is no second tooth before the middle. On the other hand the carina 

 on the under surface is much better developed, beginning as a prominent 

 tooth, where, in Williamsoni only a rounded eminence occurs, In profile 



