Occasional Papers of the Museum of Zoology 3 



and the less distinctly four-sided triangle of both front and 

 hind wings (Needham) are not mentioned by de Selys, and 

 his description of the relative lengths of the sides of the 

 triangles does not correspond with their material, and indicates 

 a narrower winged type. Nor can I see that the sectors of the 

 arculus of their specimens agree well with de Selys' de- 

 scription. • 



Aly specimens, twenty-three in number, representing two 

 species congeneric with Needham's and Ris's material, show 

 that within a species the triangles are variable in form, and 

 therefore probably worthless for generic distinctions. Char- 

 acters of the sectors of the arculus are easily misinterpreted 

 and are not always correctly represented in figures. The char- 

 acter of the stigma therefore offers the greatest difficulty to 

 referring all this material to Agriogomphus. For I now know 

 the venation of four species and in all the stigma covers two 

 and one-half cells, while in the type, Agriogomphus sylvicola, 

 which I know only from de Selys' description, the stigma 

 covers four to five cells. This is not so remarkable in itself, 

 but in wings with such reduced venation where such a differ- 

 ence exists, other and more significant differences should be 

 expected. 



I have written to Dr. Ris asking him to have a photograph 

 made of the venation of de Selys' type. In the chaotic con- 

 ditions existing a considerable time must elapse before Dr. 

 Ris can have this done, if, fortunately, my letter on the sub- 

 ject ever reaches him. 



For the present I am using Agriogomphus in the sense in 

 which all authors since de Selys have used it. Whether we 

 are right or not must be determined by a study of de Selys' 

 material at Bruxelles. 



