CC. 
GOMPHIN 2. 
to the arculus as the length of the proximal side of the internal 
triangle ; usually with two rows of postcostal cells beginning proximal 
to the level of the discoidal triangle, and three or more rows between 
the second sector of the triangle and the hind margin. 
Pterostigma with a brace-vein at its proximal end, arculus at 
or proximal to the second antenodal, distal thickened antenodal the 
fifth, one submedian cross-vein; two rows of post-triangular cells 
to at least the level of the penultimate antenodal; inferior angle 
of the ocellar triangle (seen from in front) at least 135°. Males 
with the abdomen widest at the eighth segment; tibial spines not 
differentiated, a short in‘erior carina on the distal part of the first 
tibia ; anal triangle not reaching backward to the anal angle, 
3-4-celled; branches of the inferior appendage* contiguous, 
upeurved in their apical half. Females with the auricles on 
abdominal segment 2 small, vulvar lamina * reaching to one-half 
or less of the length of segment9 . . .... 2.2.24. 
Sectors of the arculus for a short distance distal to their origin 
separated by an interval less than the thickness of either sector, 
basal subcostal cross-veins present. Front wings with the short 
sector and the first sector of the triangle divergent, with ten to 
sixteen marginal cells; proximal angle of the discoidal triangle as 
far, or farther, distally from the arculus as (or than) the length of 
the proximal side of the internal triangle; only one row of post- 
costal cells proximal to the level of the discoidal triangle, and not 
more than two rows between the second sector of the triangle and 
the hind margin. 
D. Pterostigma with a brace-vein at the proximal end; arculus at or 
proximal to the second antenodal; distal thickened antenodal the 
fifth, one submedian cross-vein, two post-triangular rows out to 
the level of the nodus (front wings), two cells, then one post- 
triangular row to level of separation of principal and subnodal 
sectors (hind wings) ; inferior angle of the ocellar triangle (seen 
from in front) about 110°. Females with no auricles on abdo- 
minal segment 2, vulvar lamina reaching to one-half the length 
of segment 9. Male of the faunal species unknown. . . . 
DD. Pterostigma with no brace-vein +; arculus distal to the second 
ERPETOGOMPHUS. 
? CYANOGOMPHUS. 
* The characters drawn from the inferior appendage of the male and the vulvar lamina of the female have 
been added to aid in distinguishing Erpetogomphus from Gomphus and Ophiogomphus. These latter two 
genera occur in Texas, New Mexico, and Arizona, and may perhaps be hereafter found in Mexico. The 
venational character given by Prof. Needham in 1897 (Canad. Ent. xxix. p. 166) for separating Erpeto- 
gomphus and Ophiogomphus from Gomphus is not diagnostic and has not been employed in his later papers. 
+ When a cross-vein does occur immediately under the proximal posterior angle of the pterostigma in 
Epigomphus, it is not in prolongation of the proximal side of the pterostigma and is not thicker than its 
neighbours—in which respects it differs ‘from a true brace-vein. 
u?2 
