36 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



of Loew's description, to be quite distinct. Loew's species 

 is described as having entirely black coxae, a black thorn- 

 like tuft of bristles on the middle coxa and bipartite hypo- 

 pygial lamella. P. effilatus has the tips of the coxae yellow, 

 a white thorn-like tuft of bristles on the middle coxa and 

 simple hypopygial lamellae. 



/ Synarthrus Loew. 



Loew established the genera Syntormon and Synarthrus 

 in his "Neue Beitrage" V, 1857, p. 35, for certain species 

 previously included in Meigen's genus Rha^hium. These 

 species agreed in having the second antennal joint overlap- 

 ping the third on the mesial side with a thumb-like projec- 

 tion. The species of Syntor?non were distinguished from 

 those of Synarthrus in having the first antennal joint hairy 

 on the upper side. Loew, when he came to describe the 

 Dolichopodidge of North America, retained the two genera, 

 but found only species of Synarthrus represented in this 

 country, i. e., species without hairs on the first antennal 

 joint. Schiner in his " Fauna Austriaca," Diptera I, p. 

 192, 1862, united Loew's genera, retaining the name Syn- 

 tormon, but discarding Synarthrus. His example was fol- 

 lowed by Mik, who found that in Syntormon rufi^es Zett. 

 the female has the first joint of the antennae naked above, 

 whereas the male may or may not have a hair on the upper 

 surface of this joint. Thus the only character on which 

 the genus Synarthrus was originally founded proved to be 

 of no value. 



When we examine the American species described by 

 Loew and the new ones here described, we find that they 

 constitute a very compact group, if we exclude Loew's 

 Synarthrus barbatus. Of this peculiar species Loew says:^ 

 " Its position in the genus Synarthrus can only be a tem- 

 porary one, brought about by the difficulties of placing it 

 into another genus. It is sufficiently distinguished from the 

 other species of Synarthrus by the pecularity alone, that 



iMonog., p. 134. 



