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 (yvfivos naked, and Tttipvy the sole) 

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

 whereby it differs from the genus Dolichopus, to which its species 

 formerly belonged. 



The species described by Say as Dolichopus obscurus seems to 

 be a Gymnopternus. 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. 

 As 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. 



Table for the determination of the Species. 



, f Color non-metallic. 1 flavus Lw. 



1 Color metallic. 2 



n ( Third joint of the antennnp with an elongated point. 2 subulatus Lw. 



I Third joint of the antennae without elongated point. 3 



feet black. 4 



lg color of th<' feet yellow. G 



4 ( Third joint of the antennae remarkably hairy. 3 scotias /-»•. 



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



g ( Wings grayish hyaline. 4 barbatulus Lw. 



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



o ( Prevailing color of the 

 ' Prevailing color of the 



