Cockerell — A Fossil Tsetse Fly and Diptera from Florissant. 21 



it requires a strong light and close study to make it out. The side of the 

 fifth posterior cell on the second basal appears to be less than that on 

 the discal, which is not usual in Oxycera ; the vein separating the sub- 

 marginal cells is so extremely faint that I thought it was absent, as in 

 0. formosa Meigen ; the end of the stigma is about on a level with end of 

 discal cell; the longitudinal veins from the discal cell are straight or 

 practically so. The following measurements in microns were taken with 

 difficulty, but are probably correct: Depth of submarginal cell at level 

 of end of stigma 272, discal cell on first posterior about 720, discal on 

 second posterior 128, discal on third posterior 256 or perhaps more, discal 

 on fourth posterior 320, discal on fifth posterior 384, second basal on fifth 

 posterior 288; end of anal to wing margin 20S. 



Miocene shales at Florissant (Geo. Wilson). 



I am unable to demonstrate the scutellar spines, and they were possi- 

 bly absent, so it is not positive that the fly belongs to Oxycera. Of the 

 genera of Clitellariinae cited by Williston without scutellar spines, this 

 can not be Nemotelus or Akronia, as the face is not conically produced; 

 the size and appearance are quite unlike Hermetia or Chrysochlora ; the 

 bare eyes exclude Pelagomyia ; leaving only the South American genus 

 Cacosis of Walker, which is distinguished by antenual peculiarities which 

 can not be made out in the fossil. The fossil shows one antenna ap- 

 pressed to the head, and it is oval with a stout terminal arista, as in 

 Oxycera morrisii Curtis, figured by Verrall. The fossil is therefore 

 either an Oxycera or very closely related to that genus. 



