246 S. W. Williston — New Diptera. 



tudinal, covering a stump of a vein. Four specimens. Como, Wyo- 

 ming, June 20. Long. corp. 10-11""". 



Belongs in the small Mediterranean group with hyaline discal cell. 

 Easily distinguishable from C. fulvaster O. S., of the same region, 

 the only other known American species of this group, by its large 

 size, black frontal and facial callosities and the greater hyalinity of 

 the wings. From C. quadrivittatus Say, it is also evidently different. 



