nv R. j. TILLYARt). 58l 



We can now complete this part of the wing in Dunstania. 

 The descending vein from M3 must be the homologue of the 

 corresponding vein in Dunstaniopsis ; the only difference is in 

 the angle of departure from M3. On this difference, as well as 

 upon its more numerous and slightly more divergent veins, we 

 see at once that D unsiania had a broader and shorter membrane 

 than Dunstaniopsis. 



Following the main stem of Cu, which I call Cun,, across the 

 dividing line in Dunstaniopsis, we see that it continues in a 

 gentle curve, until it ends up on the dorsum of the wing, not far 

 from the tornus. Below Cu^,, another branch of Cu, Cu„, arises 

 on the dividing line, and passes into the membrane as a curved 

 vein running to the dorsum below Cuj. 



The dividing line hereabouts is not well preserved, but its 

 ending up on the dorsum can be just made out. The division 

 between corium and membrane is clearly noticeable in the fossil 

 on account of the difference between the colour of the rock and 

 the fossil itself. The former is a dark grey; the latter a pale 

 brown, 'i'he vvhole of the corium is coloured pale brown, and is 

 Hat and smooth. The membrane, on the other hand, is vari- 

 coloured, showing pale veins bordered by narrow bands of dark 

 brown pigment, and, between these, areas of the darker rock- 

 colour on those parts where no veins are present. Also, the 

 membrane is lightly pitted all over, whereas the corium is quite 

 smooth in this genus. 



Sufficient will now have been said to make it abundantly clear 

 that we have, in Dunstania and its allied genera, a primitive 

 type of Heteropteron, of large size, and very probably of amphi- 

 biotic habits. From recent Heteroptera, such as the Lyyceidce 

 and PyrrJiocorid(e^ in which some of the venation is still pre- 

 served upon the corium, the DunstaniidcB differ in the incom- 

 pleteness and tortuosity of the dividing line between corium and 

 membrane: and they show us how the anterior portion of this 

 dividing line has been evolved, apparently in a most complicated 

 manner, from a series of cross-veins and branches of main-veins 

 linking up at different angles. Tiie process by which the straight 

 division between corium and membrane, found in most recent 



