240 



FOSSIL INSECT WING, OHDER PARAMECOPTERA, 



sometimes increases in length, and may be seen traversing the 

 cubitus in the imaginal wing. Again, in most species of Rhya- 

 cophila (rightly regarded as being one of the most archaic of 

 existing Trichopterous genera), the posterior arculus is well 

 developed; but other species exist in which it is reduced to a 

 short cross-vein, or even obliterated by complete fusion of M 

 with Cu,. Which of these conditions is the most archaic 1 



Text-fig. 3. 

 Belmontia mitchelli, n.g. et sp., to show the preserved portion of base of 

 forewing, enlai'ged, ( x 17). Upper Permian of Belmont, N.S.W. 

 For lettering, see Text-fig. 2, p. 238. 



In our new fossil, as can be seen from Plate xiii. and Text-fig. 

 3, the posterior arculus appears as a very strongly formed convex 

 vein. If it is a cross-vein, then it is very different from any 

 other cross-vein in the wing, since all the others are much more 

 weakly chitinised. Now I have already shown, in a previous 

 paper (5), that, in all archaic Panorpoid types, macrotrichia are 

 present upon the main veins and their branches, but are absent 



