Dll'TERA— MYCETOPHILID.E. 595 



they divide near the center of the wing, and the fifth and sixth longitndinal 

 as near the base as the third and fourth; the sixth longitudinal vein is 

 straight, and appears to reach the margin of the wing. 



The genus resembles Boletina more than any of the genera figured by 

 Winnertz, but differs strikingly from it in tlie approximation to the base of 

 the forking of the third and fourth, and of the fifth and sixth longitudinal 

 veins. In this particular it closely resembles the Sciarina, but on the other 

 hand differs from them to a greater degree in the length of the auxiliary 

 and first longitudinal veins, and in that the former reaches the costa. The 

 costal vein does not appear to pass beyond the tip of the second longi- 

 tudinal vein, but this point is obscure. 



I have dedicated this genus to the distinguished dipterologist, Baron 

 Osten Sacken, to whom I am indebted for many suggestions in the deter- 

 mination of these fossils. 



Sackenia arcuata. 



PI. 5, Figs. 3, 4, 12, 13. 



Sackenia armata Scndd., Bull. U. S. Geol. Geogr. Surv. Terr., Ill, 754-75.5 (1877) ; in Zittel, Haudb. d. 



PaheoDt., I, ii, 811, Fig. 1088 (18rf5). 



This species is represented in part by a female specimen, more than 

 usually well preserved. The body is pale testaceous; the wings wholly 

 hyaline, but the veins faint testaceous; the antenuce are a little longer than 

 the head and thorax together, very slender, of the color of the thorax ; the 

 basal joints are subglobular, slightly broader than long, the remainder twice 

 as long as broad, and beyond the middle of the anterinaj slightly monili- 

 form. In the wings, the base of the hinder cell, using Winnertz's terminology, 

 lies within the base of the upper discal cell, both being nearer the base of 

 the wing than the middle transverse vein, while the base of the middle dis- 

 cal cell is far outside of either of these, near the center of the winjr. The 

 costal vein appears to terminate where the cubital reaches the margin, and 

 the axillary vein nearly or quite reaches the border. The legs are partly 

 detached, and the basal poi'tion of the front pair obscure, but it looks as 

 though the front tarsi were about three times as long as the front tibiae, 

 which is hardly probable. 



Length of body, 5.(^5"'"; antennae, 2"" ; wings, 4.25"""; hind femora, 

 3""; hindtibiaj, 2™"'; hind tarsi, 2.4"""; fore tarsi, 2""'. 



