/ |/|/| NEW YORK STATE MUSEUM 



easily referable at a glance to their place in the genus. The imagos ex- 

 hibit with slight variations one color pattern, one plan of venation, one 

 habitus, and are therefore not easy to distinguish. I give below an arti- 

 ficial key to aid in the recognition of our species, and follow it with a 

 synoptic arrangement of the genus, in which is included a statement of 

 the more important characters of lesser groups within the genus. For 

 all of these I prefer to retain the old generic name Gomphus till more of 

 the nymphs are known. 



ARTIFICIAL KEY TO IMAGOS 



1 Face entirely yellow 2 



Face yellow, transversely banded with black 10 



Face suffused with brownish black ; large, very elongate species, with a dis- 

 tinct anal loop of a single cell, a pair of narrow oblique yellow stripes on 

 the dark background of the thoracic dorsum 14 



2 Hind margin of the occiput with a distinct median tooth...... villosipes 



'' without '' 3 



3 Tibiae yellow externally 4 



" black " 7 



4 Abdominal segments 7-9 strongly dilated about as wide as the thorax 



f r a ternu s 

 Abdominal segments 7-9 little dilated, much narrower than the thorax. .. 5 



5 Length under 45 mm exilis 



Length over 45 mm 6 



6 Superior abdominal appendages of the male with a sharp inferior tooth ; 



vulvar lamina of the female composed of two acute triangular lobes, one 



fourth as long as the ninth segment 8j)icatus 



Superior abdominal appendage of the male with a low inferior lobe; vulvar 

 lamina of the female composed of two low rounded lobes, and hardly 

 loni;er than one 10th of the ninth segment sordidus 



7 Length under 40 mm abbreviatus 



Length over 40 mm and under 50 mm 8 



Length over 50 mm 9 



8 Abdominal segments 7-9 greatly dilated, as wide as the thorax 



ventri cosus 

 Abdominal segments 7-9 little dilated, much narrower than the thorax 



quad ri color 



9 Dorsum of the 10th abdominal segment and the superior appendages 



black descriptus 



Dorsum of the 10th abdominal segment and the superior appendages 

 yellow furcifer 



10 Yellow of the thoracic dorsum reduced to two narrow, oblique, isolated, 



yellow stripes scudderi 



Yellow stripes of the thoracic dorsum broader, not isolated, dilated at 

 their anterior ends 11 



11 Side (anterior face) of the hind femora yellow amnicola 



Sides of the hind femora black 12 



