Ij^ Ccinariian ^ntawalajbt. 



Vol. XL. LONDON, JUNE, 1908. No. 6. 



TWO FOSSIL DIPTERA. 



BY T. D. A. COCKERELL, UNIVERSITY OF COLORADO. 



The finest fossil insect found at Florissant by the expedition of 1906 

 was a large and excellently-preserved Asilid fly. Although several fossil 

 Asilid^e have been described from Europe, only one species {Stenocinclis 

 aiiomala^ Scudder, from Wyoming) has been described and named from 

 the American tertiaries. 



Microstylum Whee/eri, n. sp. 



Length about 40 mm., of which 14 or a little less is head and thorax; 

 wings rather short, about 20}^ mm. long, faintly dusky, the veins dark ; 

 head and thorax black ; legs very dark brown or piceous ; abdomen 

 reddish-brown, with triangular black markings on the first four or five 

 segments, as shown in the figure ; antennae stouter than in M. morosiun^ 

 Loew. The general form and proportions are shown so well in the figure 

 that they need not be described. (Plate 4.) 



The venation appears to accord sufiiciently well with that of 

 Microstylum. The radius and radial sector are quite normal, the latter 

 branched as in M. viorosiim ; radiomedial cross-nervure present and 

 normal ; the cell between the ultimate branches of the media is essentially 

 as in M. inorosum, the upper branch being even more bowed basally, but 

 the efid of the upper branch reaches the margiii a considerable distance 

 from the lower branch of the radial sector ; cell Vg (Comstock's Manual), 

 which I consider to be enclosed within the branches of the cubitus 

 (following my interpretation of the venation in the Nemestrinidae), is 

 spindle-shaped, with the upper margin not far from straight, but the lower 

 strongly bowed ; from its apex it sends a cross-nervure to the media, 

 reaching tlie latter at the point of forking, and a straight nervure (end of 

 the cubitus according to my interpretation) to the margin ; there was no 

 doubt a cross nervure passing from its lower side to the margin, but this 

 place is obliterated ; the cubital cell (viii, Comst.) is very narrow. 



According to my interpretation (Amer. Jour. Sci., x'\pril, 1908) the 

 strong bend in the upper branch of the media is perhaps a relic of a 

 condition in which a cross-nervure (found in most Nemestrinids) passed 

 from thence to the radial sector \ no trace of this now remains. 



