Vol. xxvii | ENTOMOLOGICAL NEWS. 3209 
Acanthagrion adustum Williamson, figs. 20-21. A thin septum-like, 
median, internal hook pointing distad on segment 3. 
Acanthagrion apicale Selys., figs. 3-4. Segment 3 with a pair of 
heavy, chitinized, terminal hooks between which is a median globular 
swelling. 
Acanthagrion ascendens Calvert, figs. 12-13. A median internal api- 
cal hook on segment 3. 
Acanthagrion cheliferum Selys., figs. 26-27. An internal median 
swelling on segment 3. A thin, chitinized median hook on segment 
2. Terminal fold well developed. The ridges in fig. 27 may have been 
due to the drying of the preparation. 
Acanthagrion cuyabae Calvert, figs. 16-17. A median internal enlarge- 
ment between the two lateral lobes of segment 3. 
Acanthagrion “gracile” Rambur, figs. 8-9. Peculiar in that the tip of 
segment 3 is divided horizontally into three septa. 
Acanthagrion indefensum Williamson, figs. 22-23. A delicate me- 
dian, internal, barbed hook on segment 3. 
Acanthagrion interruptum Selys., figs. 5-7. A median internal hook 
on segment 3. See fig. 7. 
Acanthagrion kennedii Williamson, figs. 14-15. A thin septum along 
the median, internal line of segment 3. - 
Acanthagrion laterale Selys., figs. 18-19. The most simple of the 
series having merely an internal, median swelling to indicate its re- 
lationships. 
Acanthagrion temporale Selys., figs. 1-2. A thin septum as in ken- 
nedu. 
Acanthagrion truncatum Selys., figs. 24-25. A median internal hook 
formed by the turning in of the edges of segment 3. 
In conclusion, certain venational characters divide this 
genus, as it has been understood in the past, but the penis, be- 
cause of its evident great variety of forms, is of little assist- 
ance in defining groups among this series of species. How- 
ever the study of the penis has shown very definitely that we 
are dealing with structurally, well defined species rather than 
with subspecies and varieties based, as hitherto, largely on 
color. 
In addition I might say that I shall treat in another paper 
of a series of species in which a condition exists just opposite 
to this which occurs in Acanthagrion. In this other series 
what are apparently generically distinct species have almost 
identical penes. 
