Occasional Papers of the Museum of Zoology 9 



Only the discovery of more specimens can tell how valuable 

 as a character for erecting a genus, distinct from Cyanogom- 

 phus, the front wing anal area of one cell width may prove. 

 In the group of genera to which this proposed new genus. be- 

 longs venational specialization has not been carried as far as 

 in other genera in the legion Gomphus, a fact which weakens 

 this character for purposes of generic definition. 



It may be noticed by comparing the descriptions and figures 

 of the second hamules of the males of Cyanogouiphus zvalth- 

 cri, C. conchinns, and Ischnogoniphus jcssci that in the first 

 two there are apical tufts of hairs which are entirely lacking 

 in the third. But against this, one may set the peculiar first 

 hamule which is very much alike in C. ivalthcri and-/, jcssei. 

 The form of the tibiae of /. jessei is a striking character. In 

 dragonflies generally the tibiae are roughly triangular or semi- 

 circular in cross section, but in /. jcssei they are on all three 

 legs rectangular in cross section, being nearly square, and the 

 four- sides are flat and the angles well defined. The third 

 tibiae of C. conchinus show this character less perfectly, but in 

 /. jcssei it is equally well developed in all the tibiae. The in- 

 ferior abdominal appendage of the male is very similar in 

 C 2^'altlicri and C. concJiinus, and very different in /. jcssci. 

 ^Moreover the apex of segment 10 is much more nearly the 

 usual form in /. jessei, while segment 9 has the dorsum strong- 

 ly produced apically (or the sides apically excavated), in 

 marked contrast to segment 9 in the two species of Cyano- 

 gouiphus where the segment is of the usual form, ^^'hen 

 Cyanogoinphiis tnmcns is better known it may be found to be- 

 long to another genus. I believe such will prove to be the 

 •case and it is not improbable that it will be found to more 

 resemble Ischnogomphus than the eastern South American 

 Cyanogomphus. 



