X74 DIPTERA OF NORTH AMERICA. [rART II. 



a. Costa of the male incrassated. 



7. costalis Lw. 8. subcostatus, nov. sp. 



b. Costa of the male not incrassated. 



9. discolor Lw. 10. auratus Lw. 



B. Femora of a pale color. 



11. pallipes Lw. 12. picticornis, nov. sp. 



Description of the Species. 



I. Third joint of the antennae elongated. 



1. C. COrniltllS, nov. sp. % . — Obscure viridis, paulo nitens, tertio 

 antennarum articulo elongate oculis infra antennas contiguis, tegularum 

 ciliis femoribusque nigris, tibiis testaceis, tarsis anterioribus inde ab 

 articuli priuii apioe posticisque totis fuscis. 



Dark green, little shining ; the last joint of the antennae elongated, eyes 

 meeting below the antennae ; cilia of the tegulae and femora black ; 

 tibue brownish-yellow ; the four anterior tarsi from the tip of the first 

 joint and all the hind tarsi brown. Long. corp. 0.09. Long. al. 0.09. 



Dark green, moderately shining. Antennae black, the third 

 joint uncommonly elongated for a Chrysotus, almost of the same 

 shape as in the species of Argyra, only somewhat longer, with a 

 blunt tip ; arista apical. Front black-green. Coxae and femora 

 black, the latter with brownish-yellow tip. Tibiae brownish-yel- 

 low, the hindmost black-brown at the tip and fringed on their 

 upper side with a moderate number of bristles. The four anterior 

 tarsi are black-brown from the tip of the first joint ; the hind tarsi 

 are of a black-brown color. Cilia of the tegulas black. Wings 

 of the usual structure peculiar to the genus Chrysotus, hyaline 

 with a gray tinge ; the small transverse vein is before the middle 

 of the wing and is short. 



Hab. Illinois. (Le Baron.) 



Observation. — This species is distinguished from all other spe- 

 cies of the genus Chrysotus in a striking manner by the unusual 

 elongation of the third joint of the antennae, agrees, however, com- 

 pletely in all other respects. I have hesitated to establish a new 

 genus upon it, as but a single character constitutes its difference 

 from Chrysotus, which character belongs probably only to the 

 male. 



