2 54 Annals Entomological Society of America [Vol. 11^ 



(6) Base of discal cell with a diameter of 425; apex rounded 

 and quite remote (a distance as great as the length of the anterior 

 cross-vein) from the lower corner of the first posterior cell. This is 

 unlike the three recent species compared, but the character occurs, even 

 more pronounced, in Brachyopa notata and other Syrphidae. The outer 

 side of the first posterior shows a very strong double curve, and the 

 apex of the cell is quite remote from the margin; all this essentially 

 as in Baccha dimidiata. 



(7) Cross-vein from anal to discal cells about 595 long, thus con- 

 siderably longer than base of discal, which is not at all the case in the 

 recent forms compared. This condition exists in Xylota pigra, but 

 usually when there is a difference, it is the other way among the Ameri- 

 can Syrphidae. 



(8) Anal cell normal, closed some distance from margin of wing. 



Habitat. — Miocene shales at Florissant, Colorado, 1909 iyVil- 

 lard Rusk) . The specific name suggests that it may have fed on 

 the genus of Aphid idse, most abundant in the vicinity. The 

 insect seems not to be quite typical Syrphtis, but it appears to go 

 better there than elsewhere. Easily known from S. willistoni 

 Ckll., also fossil at Florissant, by its larger size. 



Dioctria (?) florissantina (Ckll.) (Asilid£e; Dasypogoninse) . 



When describing Leptis florissantina (Am. Jn. Sci., Jan. 1909, 

 p. 58), I did not attach enough importance to the length of the 

 second vein. Renewed study shows that the venation is exactly 

 that of the Asilid genus Dioctria, except that the cell in the forks 

 of the third vein does not widen apically. The abdomen also 

 agrees with Dioctria, but the thorax is much too broad and round- 

 ed in front, and the head and eyes, while ordinary for a Leptid. 

 do not look like those of an Asilid. It is possible, however, that 

 they are somew^hat distorted. 



Microstylum (?) destructum sp. nov. (Asilidse; Dasypogoninae.) 



This insect appears to represent a new genus, but by a great 

 misfortune the pick fell so as to shatter and destroy the whole of 

 the apical half or more of the wdngs and abdomen, and it is not 

 desirable to attempt a generic diagnosis from what remains. 



Body exceedingly robust, head and thorax shining coal-black, the 

 latter about (J mm. long; structure of head not ascertainable; abdo- 

 men reddish-bro\yn with the sutures hyaline, 6J mm. broad at base; 

 legs slender, dark, hind femur 765 /^ broad near end, without bristles; 

 hind tibia about 544 ix broad, with very small inconspicuous bristles. 



Venation agreeing with Microstylum flaviventre, so far as pre- 

 served, except as follows: 



