BY R. J. TILLYARD. 721 



to argue that the present-day broad hindwing and specialised anal 

 loop of the Lihellulince was developed secondarily from a wing in 

 which the original broad Anisopterous hindwing had been reduced 

 to approximately equal width with the forewing. If not, we should 

 rather accept a theory of the development of all the present-day 

 loops from a broad-winged but very generalised archaic type, to 

 which Chlorogomphus may hold the clue, and regard all the nar- 

 row-winged forms, even if proved archaic, to be the result of asthe- 

 nogenetic convergence. The former theory is strongly held by Dr. 

 Ris, whose opinion, as without doubt that of the most accomplished 

 Odonatologist of the present day, cannot be lightly put aside. To 

 me, however, the latter seems to be by far the more probable. 



Let us first of all, therefore, compare both larval and imaginal 

 forms of NannopJilehia and Cordulepliya* : — 



A. Larvse: — 



(1) The labia. — These are very distinct, Cordulepliya showing 

 high specialisation in several points. Compare «, the long narrow 

 gulf-like incisions of the upper part of the inner margin of the 

 lateral lobe in Cordulepliya, with the normal crenations of Nanno- 

 phlebia; h, the much longer end-hook in Cordulepliya; c, the more 

 numerous and more strongly developed setas, both lateral and men- 

 tal, in Cordulepliya; d, the larger number of spines (3-4), on the 

 lower (normal) crenations of Cordulepliya; e, the finely speckled 

 or spotted surface of the lateral lobes in Cordulepliya, with the few 

 but larger and more conspicuous black spots on Nannophlehia. 

 One cannot but conclude that Nannophlehia is really more closely 

 allied, in its labium, to the main Eucordulian stock, than it is to the 

 distinctly aberrant Cordulepliya. 



(2) The antennoi. — Though both are seven-jointed, those of 

 Nannophlehia are very much shorter than those of Cordelphya. 



(3) The legs. — Those of Cordulephya are very much the longer. 

 (4:) The ahdomen. — In Cordulephya, segment 10 is fully recessed 



into 9 ; while in Nannophlehia, it is normal in position. [The ar- 



* For characters of Cordulephya, see Plates xi. and xii., pp. 421-2, These 

 Proceedings, Vol.xxxvi., Part 2, 1911. 



