274 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxm. 



i. Stigma long, in front wing equal to more than one-fourth the dis- 

 tance from nodus to distal end of stigma; triangle in hind wing 

 greatly elongated, the upper side about twice as long as the 

 inner side; basal antenodal of second series present in both 

 wings; M4 and Cuj in front wing divergent, 3 rows of cells 

 between at level of the nodus; 2 rows of cells between M.^ and 

 Mia in front wing at level of distal end of stigma; 2 rows of cells 

 between Mj and M2 in front wing beginning nearer the stigma 

 than the nodus; arculus in front wing at or proximal to second 

 antenodal; cubital space in front wing with 1 cross vein in 

 addition to the inner side of the subtriangle; anal area in front 

 wing with 1 row of cells jjroximal to the triangle, followed by 

 a maximum width of 3 cells or more; 3 rows of postanal cells in 

 hind wing; distal angle of triangle in hind wing not separated 

 from M4 by a distinct stalk; stigma with brace vein. 



Cydogomphus 

 a. Stigma shorter, at the most equal to or less than one-fourth the 

 distance from nodus to distal end of stigma; triangle in hind 

 wing with upper side not twice as long as the inner side; basal 

 antenodal of second series usually absent. 

 j. Cubital space in front wing with 2 cross veins in addition to the 

 one forming the inner side of the subtriangle; M4 and Cu^ in 

 front wing with 3 rows of cells between at level of nodus; 2 

 rows of cells between Mj and Mj^ in front wing at level of distal 

 end of stigma; arculus in front wing distal to second antenodal; 

 anal area in fi-ont wing with 2 rows of cells proximal to the tri- 

 angle, beyond the triangle but little better developed, nor- 

 mally only 2 cells wide at the maximum; 4 rows of postanal 

 cells; distal angle of triangle in hind wing not distinctly 

 separated from M4; brace vein of stigma apparently variable. 



Anisogomphus 

 jj. Cubital space in front wing with one cross vein in addition to 

 the one forming the inner side of the subtriangle. 

 k. Triangle in hind wing not distinctly separated from M^ by 

 a short stalk; usually 2 (sometimes 3) cross veins between 

 Mi_3 and M4 in front wing. 

 I. A2 in hind wing arising near the middle of the lower side of 

 the subtriangle, postanal cells of about the same width 

 throughout; arculus in front wing at or proximal to second 

 antenodal; 1 or 2 rows of cells between M^ and Mi^ in 

 front wing at level of distal end of stigma ; 2 cells between 

 Mj and M, in front wing beginning nearer stigma than 

 nodus; stigma with brace vein. 



cases, and, in the resulting confusion, relationships are almost impossible of discern- 

 ment. At the same time I believe the genera may be accurately defined, though 

 their proper grouping is impossible, by venational characters alone. Material access- 

 ible to me, as ex^jlained more fully in the following pages, has been such that I have 

 been limited to a first-hand study of venational characters only, in the case of many 

 genera, and in the case of all to but few specimens and species. It is to be expected, 

 therefore, that the arrangement of genera is not entirely a natural one and that the 

 definitions in many cases are too explicit to cover all the species. More material, 

 both adult and nymphal, than that to be found at present in all the collections in 

 the world and the tabulation of other as well as venational characters will be necessary 

 for the ultimate solution of the relationships of these genera. 



