252 
[October 
of this appendage; in vastus there are slight rudiments only of such a 
flange, which I omitted to mention in my description, for the sake of 
brevity. 
G-. FLUViALis Walsh, and Gr. amnicola Walsh. I ought to have 
stated as one of the sexual distinctions of these two closely allied spe¬ 
cies, that the terminal joints of the 9 abdomen are not nearly as much 
dilated as in % —in fact scarcely dilated at all. In the % the ter¬ 
minal joints are dilated about f as much as in G. fraternus. In this 
respect these two species differ from the characters of the group palli- 
dus (Selys,) which is the only one to which they can with any propriety 
be referred, and which is stated have the terminal joints ( S 9 ?) “very 
little dilated.” (Mon. Gromph. p. 118.) They differ also in the % ab¬ 
dominal appendages not being “yellowish,” but brown-black or black. 
They are likewise unlike pallidus and certain allied species” in the % 
not having its femora “ very hairy,” but on the contrary destitute of 
any but a few scattering basal hairs which are also found in 9 . Pro¬ 
bably they form a distinct group. 
Of the great genus Gomphus there are now no less than 86 described 
species, including the three described above and the six described in 
my former Paper on Pseudoneuroptera. Of these 86 no less than 36 
occur in North America, and at least 26 and perhaps 30 within the 
limits of the United States. Messrs. Selys and Hagen have divided 
this Grenus into 16 subgenera, six of which are found in America, 
either North or South, and five within the limits of the United States. 
The following Synoptical Table expresses as briefly as possible the 
structural relations of these six American subgenera. In giving more 
weight to structure and less to coloration I have deviated from the 
path travelled by M. Selys in his Analytical Table of the whole num¬ 
ber of Subgenera. (Mon. Gromph. p. 14.) 
