232 Journal New York Entomological Society. [Voi. xx. 



arcuation short, scarcely longer than ilfj+o between cross-veins r-in and m ; 

 basal deflection of C?(i-before the middle of cell ist M,. 



Abdomen : tergum brown, the base of the sclerite paler, more yellowish ; 

 sternum pale, the median markings pale brown, broadly ovate, not elongate or 

 black. 



Paratype No. i differs in having: the tibiae unicolorous throughout, 

 dark brown. 



Paratype No. 2 has the tarsi much lighter, yellowish. 



Paratype No. 3 is much larger (largest measurements given). 



Holotype, c?", Wismar, British Guiana. (Williamson, Coll.) Jan. 

 30, 1912. 



Type in author's collection. 



Paratype No. i, c?, with the type. 



Paratype No. 2, Paramaribo, Dutch Guiana. (Miss ]\Iayo.) (In 

 Coll. Acad. Nat. Sci. Phil.) 



Paratype No. 3. Manaos, State of Amazonas, Brazil. (Miss 

 Merrill.) (In Coll. -U. S. Nat. Mus.) 



B. zvilliamsoni is a sinall species finding its nearest relative, appar- 

 ently, in brevivcntris Wied. It differs from this species in the pale 

 tibial tips; the oval brown markings on the abdominal sternites (these 

 being linear and brownish-black in brevivenfris and most other spe- 

 cies), and in different wing-pattern. I take pleasure in naming this 

 interesting form after Mr. E. B. Williamson, of Bluffton, Indiana, 

 who collected the types while in Guiana in 1912, in search of Odonata. 

 Brachypremna similis Williston, 

 1900. Brachypremna similis Will., Biol. Cent.-Amer., Dipt, i, Supplement, p. 



229. 1902. Brachypremna similis Kertesz, Cat. Dipt., Vol. 2, p. 265. 



Head : rostrum, light brownish-yellow, darker on the side ; nasus brown 

 with brownish-yellow hairs ; palpi mostly brown, in some specimens the two 

 basal segments are light yellow. Antennae with the basal segments pale, yellow- 

 ish ; segments three to five, brown at base, pale at apex ; remainder of the 

 antennae brown. Front, vertex and occiput dark brown, except a narrow yellow 

 margin immediately adjoining the eyes. 



Thorax : prasscutum usually with the pale narrow median stripe not distinct 

 (in some specimens it is apparent behind, in the vicinity of the suture), the 

 pale stripes separating the broad lateral stripes from the median vitta are 

 narrow and ill-defined; scutum dark brown on the lobes, paler medially; post- 

 notum with the median brown vitta broad, the adjoining pale stripes very 

 narrow. Pleurae pale, spotted with brown, these brown marks being on the 

 margin of the sclerites. Halteres brown, the root of the stem paler. Legs : 



