738 



PERMIAN AND TRIASSIC INSECTS FROM N.S.W., 



P. australica. This irregularity takes the form of a very weak 

 zigzagging of the main veins as they pass from one cross- vein 

 below to another above, alternately It is a specialisation from 

 an originally regular condition, and is the direct result of the 

 cross-veins becoming arranged in the most advantageous position 

 as supports, i.e., alternately above and below each main vein. 

 The same line of evolution can be seen in the Odonata, where it 

 affects alternate main veins only {e.g., M4 and Cug in many 

 Agrionidcn), and in the radial sector of Planipennia. On these 

 grounds, therefore, we are justified in considering P. australica 

 to be represented by a hindiving. 



Rx...-P^ 



Text-fig.7. 

 Tivniochorista paU (da Esh.-'Pet.; wings. Recent; Brisbane. For com- 

 parison with Permochorixta. The dotted cross- veins are obsolescent; 

 //•, frenulum; jh, jugal bristle; jl, jugal lobe; jp, jugal process; pf, 

 pterostigmatic furrow; pt, pterostigma. 



Turning now to the less complete P. mitchelli, we see at once 

 that it more closely resembles the forewing of T. pallida, not 

 only because of its greater breadth towards the base, but also 



I 



