ADAMS : NORTH AMERICAN DIPTERA. 445 



ter black. Abdomen black, pile \Yhite, dorsum of second and 

 following segments, when viewed from before, solid sericeous, 

 scarcely perceptible from behind, hind border of second seg- 

 ment white pollinose, venter shining, except the narrow hind 

 border of the second segment, pile white, tip of hypopygium 

 yellowish. Cox?e and legs black, pile white, bristles black, 

 front tibise anteriorly, middle and hind tibiae posteriorly, yel- 

 low, and with coating of white pollen, base of middle and hind 

 tarsi yellowish. Wings hyaline, with two brown cross-bands, 

 one from stigma to apex of fourth posterior cell, the second 

 from apex of second vein across submarginal cells to apex of 

 first posterior cell. 



The female resembles the male except the pile of front and 

 face is not so thick, and the abdomen is not sericeous. Length, 

 male, 9 mm., and female, 10.2 mm. 



A specimen of each sex from Oak Creek canyon, Arizona. 

 Collected by Dr. F. H. Snow. This species resembles certain 

 forms of Psilocephala, but the pilosity of the face leaves no doubt 

 of the generic position. 



Scenopinus mirabilis, n. sp. 



Female : Black, head and thorax subopaque, abdomen shin- 

 ing, with short white pile ; first antennal joint slightly shorter 

 than the second, closely applied to it, their separation difficult 

 to see ; third joint twice as long as the first two together, 

 tapering somewhat from the middle apically ; a small spot on 

 humeri, and halteres yellow, abdomen broad and long, once 

 and a half times as long as the wings, twice as long as the 

 head and thorax together, knees and tarsi, except tips of 

 latter, yellow ; wings hyaline, veins dark brown, width of first 

 posterior cell at margin of wing is scarcely equal to the length 

 of the small cross-vein. Length, 4 mm. 



One specimen ; Bill Williams Fork, Arizona. Collected by 

 Dr. F. H. Snow. Were it not for the open first posterior cell and 

 short submarginal cell, this species would well be located in 

 PseudotricJiia . 



Scenopinus electa, n. sp. 



Male : Black, with very short white pile ; head and thorax 

 subopaque, abdomen shining, hind margins of segments three, 

 four and five white ; lower half of eyes of smaller facets than 



