GYMNOPTERNUS. 77 



rounded ends, and the length of which is greater than their breadth. 

 I have, then, called them rounded, without further remarks about 

 their form ; to prevent mistakes, however, I must state that this 

 applies only to the convex edge. I have omitted other characters 

 in the descriptions, because they are common to all North Ameri- 

 can species known to me ; for instance, the presence of only one 

 bristle at the end of the hind femora, etc. 



This genus derives its name (yv^oj naked, and ttttpvij the sole) 

 from the absence of bristles upon the first joint of the hind tarsi, 

 whereby it differs fro^n the genus Dolichopus, to which its species 

 formerly belonged. 



The species described by Say as Dolichopus obscurus seems to 

 be a Grjmnopternus. I do not know of any -other species of North 

 American Gymnopternus, described by a previous author. This 

 undoubtedly arises from the circumstance that the species of Gym- 

 nopternus, on account of their small size and their apparent insig- 

 nificance, have been less noticed by collectors. The number of 

 species known to me shows that North America is very rich in 

 species of this genus. To produce a really satisfactory treatise 

 on the subject would require much more material than that over 

 which I could dispose, because the positive discrimination and 

 exact delineation of the characteristics of the species present many 

 difficulties. 



I will give now a dichotomic table for the purpose of deter- 

 mining the species, and a synopsis of the systematic arrangement. 

 A-s will be seen from the latter, the bulk of the species known 

 to me, are very nearly related and form but a single group; 

 whereas but a small number show characters which isolate them 

 from the others. 



i 



Table for the determination of the Species. 



1 ( Color non-metallic. 1 flavus Lw. 



I Color metallic. 2 



9 ( Third joint of the antennae with an elongated point. 2 subulatus Lw. 



\ Third joint of the antennae without elongated point. 3 



( Prevailing color of the feet black. 4 



I Prevailing color of the feet yellow. 6 



. ( Third joint of the antennas remarkably hairy. 3 scotias Lw. 



\ Third joint of the antennae with scarcely perceptible hairs. 5 



, ( Wings grayish hyaline. 4 barbatulus Lw. 



\ Wings somewhat tinged with blackish. 5 tristis, n. sp. 



