DESCRIPTIONS OF AUSTRALIAN ^SCHNIN^. / 'SI 



medium or nil. Anal triangle of male right-angled, strong, 3-5-celled, 

 ending somewhat above anal angle, the latter strong, right-angled. 



Front prominent, anvil-shaped (exceptionally, more or less rounded). 

 Abdomen o£ male with prominent auricles, and strongly constricted at 

 segment 3 ; that o£ female more cylindrical, segment 9 carrying a small 

 projecting shelf armed with a set of teeth. 



Type : Telepldehia godeffroyi, Selys. 



The distinguishing character which separates this genus from all others of 

 the group is the production of the subcosta beyond the nodus. Whether the 

 apparent production of this vein in the imago is really a true production of 

 the subcosta, or only an approximation to the appearance of it, caused by the 

 arrangement of irregular postnodals into two regular rows, is a question that 

 can only be satisfactorily answered by a study of the nymphal wino-. 

 Unfortunately this is not at present available. Some interestino- evidence 

 on this point is furnished by a study of the wings of the fossil ^^schnidium 

 densum, Hagen (Atlas to Handlirsch's ' Fossilen Insecten/ plate xlvii. fio-. 16), 

 in which also an apparent prolongation of the subcosta is noticeable, to a 

 considerable distance further than in Telephlehia. But it will be seen at 

 once in this figure that the dense crowding of cross-veins in the costal spaces 

 is the real cause of this result; for, on the other side of the nodus, there 

 appears an exactly similar thin straight vein lying parallel to and between the 

 casta and subcosta, which from its very position cannot be claimed as any 

 portion of a main longitudinal vein. It is well known that closely-set cells 

 tend to straighten out in rows, after the manner shown by Needham in a 

 well-known diagram *. The most advantageous position for this straio-hten- 

 ing to take place would be, of course, in a continuous line with the subcosta • 

 and, if only two rows of cells existed beyond the nodus, that is also the 

 natural (one might ahnost say, the only possible) position of straightenin o-. 



Further evidence on this interesting point may be obtained by comparing 

 the nodal area of Telephlebia (Plate 8. figs. 21-24) with some variations 

 found in the nodal area of Austrophlebia (Plate 9. figs. 17-20). Are these 

 latter variations from the normal the last remnants of a denser habit of 

 venation which Austrophlebia has eliminated — just as it has eliminated the 

 cross- veins from its basilar space, — but which Telephlebia has weakly 

 perpetuated ? Or are they the beginnings of an attempt towards denser 

 venation which has been successfully carried out in the case of Telephlebia in 

 connection with the development of the pigment-band ? The evicJence is 

 not conclusive, but the former alternative is supported by the consideration 

 'that Telephlebia appears to be the more archaic of the two formSj by reason 

 of the retention of cross-veins in its basilar space. 



It is, of course, possible that the subcostal vein in Odonata was orio-inally 

 branched of bifurcated near its extremity, and that the strengthening of the 

 * Needham in Proc. U.S. Nat. Mus. xxvi. ("190.3) p. 727. 



