644: PROCEEDINGS OF THE ACADEMY OF [DeC, 



Wings clear, with light ferruginous nervures; venation as in Geron 

 gibhosus, with anal cell closed well before wing-margin, but the 

 discal cell is produced apically above and the anterior cross-vein is 

 oblique; all the venational characters agree exactly with a Geron 

 from Colorado. 



The following measurements are in microns: first submarginal 

 cell on wing margin, 608; length of prsefurca, 400; first submarginal 

 cell on first posterior, 1,664; first submarginal on first basal, 1,456; 

 second submarginal on first posterior, about 1,920; first basal on 

 discal, 1,184; first posterior on discal, 960; lower side of discal cell 

 (on third posterior), 1,392; discal on second basal, 192; third pos- 

 terior on second basal, 288. 



Miocene shales of Florissant, Wilson Ranch {Wickham). The 

 venation absolutely agrees with that of certain species of Geron, but 

 the long, flattened thorax (perhaps partly distorted by pressure?) 

 is very unlike that genus. The antennEe and proboscis cannot be 

 made out. I suppose that the ancestors of Geron got the venation 

 of the modern flies before they got the abbreviated form and humped 

 thorax. The fossil should probably constitute a distinct genus, 

 but it may provisionally remain in Geron, pending the discovery of 

 better preserved material, 



Heteromyiella miocenica n. sp. (Helomyzidas). 



Length 5 mm., wing 4.5 mm.; head, thorax and legs black; abdo- 

 men reddish, with scattered coarse bristles; wings reddish hyaline, 

 without markings. Oral vibrissse very large; anterior (or middle?) 



tibia with straight spu-r and curved preapical 

 — _ ^ ^ bristle. Venation normal; costa with many 



-^^^'^ "~~ very short black bristles (practically as in 



'■--;,„^)^>' !;^^ Heteromyiella senilis = Heteromyza senilis 



Scudder), but no long ones; auxiliary vein 

 ^Teierog^yZJa^mjocenim. distinct, complete and separate; anterior 



cross-vein below end of first vein; first 

 posterior cell broadened in middle, the third vein distinctlj^ arched 

 upward (as in Helomyza limhata); second basal cell minute but 

 distinct, anal cell also distinct. 



The following measurements are in microns: humeral cross-vein 

 to end of first vein, 1,520; end of auxiliary vein to end of first vein, 

 400 ; second vein from point below end of first vein to wing-margin, 

 1,920; submarginal cell on wing margin (not allowing for curve), 

 592; submarginal cell on first posterior, 2,080; width of first pos- 

 terior cell at level of end of discal, 448; first posterior on discal, 



