688 MESOZOIC INSECTS Of QUEENSLAND, ii., 



and shows a slight curving close to its origin. This Rs crosses 

 from R to M obliquely, reaching the latter jiist after it has 

 divided into Mj and Mo, and crosses over both these branches. 

 It then becomes a very weakly-formed vein, which drops less 

 obliquely towards Ms, but fails to reach it, being caught up at 

 the upper proximal angle of a small, but clearly-marked, trape- 

 zoidal cellule standing upon Ms itself. 



This formation certainly supports the theory, advanced by me 

 in a previous paper, concerning the true nature of the Bridge in 

 .\nisoptera(3) — written before I had seen this fossil — except in 

 one particular. I suggested that, in the Anisoptera, trachea Ms 

 "becomes hitched on to Rs," so that the bridge itself represents, 

 in the imaginal venation, the original course of Ms, while its 

 distal prolongation beyond the oblique vein (this latter repre- 

 sented in our fossil by the piece oi Rs lying below M ) represented 

 Rs {I.e., pp. 883-4). Now, in our fossil wing, Rs practically fails 

 to reach Ms, so that the natural interpretation of the venation 

 is that not only the bridge itself, but also its continuation right 

 to the wing-border, belongs altogether to Ms, while Rs only 

 forms the subnodal vein between R and Mj, the minute crossing 

 between Mj and M.^, and the incomplete oblique vein (O) descend- 

 ing towards Ms, but failing to reach it. A very little advance 

 in specialisation in this latter region would straighten out the 

 lower end of Rs, so that the oblique vein would appear completed, 

 as in all recent Anisoptera."* 



Woodward's figure correctly shows the point of crossing of Rs 

 (jver M, and its failure to reach Ms, but quite fails to give the 

 peculiar and distinctive features of the nodus itself, and the 

 dense structure of the cellular meshwork in that rearion. 



* It is possible that Rs actually continues along the zigzag between 

 M._, and Ms for three cellules" distance, so that, if further evolution sini. 

 plilied this part to single cross-veins, the slanting vein marked O' in the 

 figure might appear as an "oblique vein." This process might account 

 for the carrying on of the oblique vein far beyond the level of the nodus 

 in ^Eschuidnun, and in many recent Anisoptera. 



