918 ZOOLOGY— INSECTS. 



above; wings hyaline, veins black; the costa and some transversals yellow; 

 pterostigma oblong, a little dilated in the middle, yellowish, darker in the 

 middle, covering nearly three ariolets; 11-12 antecubitals, 7-10 postcubitals; 

 2 discoidal ariolets ; membranula whitish. 



Length of the body, 51 millimeters ; alar expansion, 64-68 millimeters; 

 pterostigma, 2i millimeters. 



Hab. — Colorado (Mr. James Ridings); foothills and plains of Colo- 

 rado, end of September (Lieutenant Carpenter); Fort Garland, Colo., 

 June 27; South Montana and Yellowstone (Mr. C. Thomas). This is the 

 species given in my last report (p. 726) doubtfully as G. colubrinus. This 

 interesting species is very near 0. colubrinus in the appendages and genital 

 parts of the male, but different in the pattern of color on the head and abdo- 

 men, and the structure of the occiput in both sexes. 0. colubrinus is a spe- 

 cies rarely to be found in collections; even the female is not yet described. 



Taken by H. W. Henshaw in 1873, and by Dr. H. C. Yarrow at Fort 

 Garland, Colo., in 1874. 



HERPETOGOMPHUS. 



HEEPETOGOMPHUS COMPOSITUS, Hagen. 



Hcrpetogomphus compositus, Hagen, Synop., 99, 1. — Id., U. S. Geol. Surv. Terr., 1873, 

 597. 



A female of this species (No. 104 G.) was collected by Dr. H. C. Yar- 

 row in 1874 at San lldefonso, N. Mex., near the Rio Grande River. 



Hab. — Pecos River, Western Texas, Yellowstone region, Oregon, New 



Mexico. 



AGRION. 



Some specimens (Nos. 19 and 20) of this genus were collected at Taos, 

 N. Mex., in 1874, by Dr. H. C. Yarrow, but were in such bad condition that 

 it was impossible to determine the species. 



