BY R. J. TILLYARD. 



705 



:genera. While, on the other hand, the development of the anal 

 area of the hind wing in Petalia^ with its anal loop, is distinctly 

 of an jEschnine form, that of Cordulegaster is more Petalurine in 

 form. Hence, from a study of the imago only, we should be in 

 doubt as to whether Petalia and allies were, or were not, after 

 all, true jEschnine forms. 



(2) As regards larval characters, I shall endeavour to show 

 that, although the nymph of Phyllopetalia above described does 

 possess one similarity to that of Cordulegaster, it is on the 

 whole distinctly jEschnine. 



As far as I can see, it is similar to Cordulegaster in one respect 

 only, viz., that it is apparently a liver amongst debris and trash 

 on the bottom of the swift mountain-creeks. It possesses a 

 curiously wrinkled body-surface, rough legs, and flattish abdomen, 

 which go to prove this to be its habit of life. Against this we 

 must set the following considerations : — 



(a) The shape of its head, with its large rounded eyes and 

 narrower curved postocular lobes, is distinctly ^Eschnine. 



(b) A study of the labium is of the greatest importance in 

 systematic classification, and the evidence it affords should go far 

 to outweigh any argument based on less certain characters. 



l^. 



I pu.j.^^ 



A^^cMt.^ tU,. 



n 



a^.i^'U. 





In the text-figures I give outline sketches of the labia of six 



genera which bear on the point at issue. Fig.l represents that 



of Cordidegaster diastatops Selys; fig. 2 of Austrogomplius hetero- 



clitus Selys; fig. 3 of Petalura gigantea Leach; fig. 4 of uEschna 



70 



