562 GEOLOGICAL SURVEY OF THE TERRITORIES. 



liar fauna of the plains becomes more apparent on each side of the 

 mountains, with its own peculiarities. The plains east of the mountains, 

 for instance, seem to be very rich in forms of Dasypogonina ; on the 

 Pacific side the Bofiibylina, especially Awf/tma?, Uxoprosopa, &c., seem to 

 be numerously represented. The materials, however, as to this feature 

 of the fauna are not abundant enough to admit of general conclusions. 

 I will now give the result of my examination of the collections in the 

 order of the families. 



Family Culicid^. 



Twin Lakes, July 21, a species of Gulex (preserved in a bottle and 

 spoiled). 



Family Chieonomid^. 

 Twin Lakes, July 29, several specimens of minute Chironomus. 

 Eagle River, August 29, minute Ceratopogons. 



Family Simulidje. 

 Eagle River, August 29, Simulium, sp., annoyed horses. 



Family Tipulid^. 



Tipula (Twin Lake Creek), allied to T. longiventris, Lw., and resem- 

 bling it closely, but differing in the picture of the thorax. 



Tipula grata, Lw., or allied species (Pacific slope). 



Tipula macrolaMs, Lw. (Twin. Lake Creek), a species easily identi- 

 fied by the peculiar structure of its male forceps. J possess specimens 

 of it from Fort Resolution, Mackenzie River, Hudson Bay Territory. 



Several other Tipulce are too badly preserved for identification. 



Family Bibionid^. 



Bibio, sp., (? , 9 . Very like femoratus, Wild., but smaller and appar- 

 ently different; the basis of the wings (in 2 ) is pale; the forked veins 

 (in $ ) are less infuscated. (Twin Lake Creek and Colorado Mountains, 

 Pacific Slope.) 



Another Bibio (Colorado Mountains) is too badly preserved for iden- 

 tification. 



Plecia longipes, Loew (probably a synonym of Bibio Jieteroptera, Say), 

 a common species in the United States, has been brought from the Colo- 

 rado Plains. 



Hesperinus brevifrons^ Walk. (Fair Play, Colo.) I possess this spe- 

 cies from Mackenzie River, and I found it myself on Mount Washing- 

 ton, N. H. 



Family Blephaeocerid^. 



Bibiocepliala grandis, new genus and species (Colorado Mountains) ; 

 the most interesting in the whole collection. It will be described in 

 detail at the end of this report. 



Family Bomeylid^. 



JExoprosopa, sp. (Twin Lake, Creek), somewhat resembling fascipennis 

 Say, but different. A single very much damaged specimen. 



Exoprosopa decora, Loew (Colorado Plains). This is a northwestern 

 species, which I possess from Iowa, Illinois, and the Red River of the 

 North. A single damaged specimen. 



Bxoprosopa, sp. (Colorado Mountains). A single, indifferently pre- 

 served specimen. 



Anthrax siniiosa, Wild. (Twin Lake Creek and Colorado Mountains, 

 Pacific slope). A rather common species in the United States. Five 

 specimens. 



