420 TWO FOSSIL INSECT WINGS IN OOLLECTXON OF MR. JOHN MITCHELL, 



tion leading- to the Aphiidae must show a continuous tendency towards the nar- 

 rowing of tiie ■ wing-base, together with a steady movement of the points of 

 origin of Rs, M and Cm distad along tlie iirimary vein. Rs appears to be 

 generally a simple vein in tlie Aphiidae, as in the Psi/Uida?. But, if we use the 

 position of the thickened stigraatic area as a guide, it would seem that, in the 

 Aphiidae, this simplicity has been attained by the suppression of R|)_|.3. The 

 fact that the distal iiurtion of Rs in the Aphiidae is concavely curved to the 

 costa would also suppoif this contention. Corrclaied with the narrowing of the 

 wing basally, the prinurry vein in the Aphiidae becomes perfectly straight, and 

 npiiroaches near to the costa in position. Cu2 -(- 1^., on the other hand, becomes 

 fused with tlie primary vein, and moves upward, following the distal movement 

 of Rs, M and Cui. In some forms an extra fork appeai-s on Mi^j, but has not 

 yet become fixed in every case. (I have seen this extra fork on one forewing 

 onlii, not only in Aphiidae, but also occasionally in Psifllidae) . Text-fig. 5 shows 

 ihe typical veiiiition of the forewiug of an .\phid, for comparison with Text- 

 figs. 3 and 4. 



Text-fig. 5. DijiLjnun of the venatioual scheme in the forewiug of the Kaiiiiiy Aphiidae, 

 showing M with the extra branch present. 

 For venational notation, see Text-fig. 1 above. 



II would seem, then, reasonable to recognise in Lophioneura a liighly archaic 

 Sternorrliynchous type, (probably standing quite close to the arciictype of the 

 group), from which, through the long ]ieriod of geological time between the 

 Upper Permian and tlie first appearance of tiie true PsyUidae and Aphiidae, 

 changes along two different evolutionary lines have led to tlie venational types 

 of these two families. 



lx>P]ii()NKLi!A irsTii,.\TA, u.sp. (Plate XXXV., fig. 2; Text-fig. 3.) 



Ko re wing: Length, 5.7 iimi; breadth, 1.9 mm. 



The sjiecinien is the east of a complete right wing, lying longitudinally 

 upon Ihe midrib of a small frond of Glossopteris sp., the base of the wing being 

 towards the apex of tlie frond, and 10 mm. from il. (See Plate xxxv., lig. 2). 

 The impi-ession is perfect, but for slight indistinctness (d" the ))iusal portion of 

 the co.sta and (d' a portion of Mj ,21 whei'e the rock appears to have been scraped. 

 The costal niargin is delicately foimed from base uj) to end of Ki, but from 

 there on almost to apex it is strongly formed, and appears to be made up of 

 the true costa fused with Ri, which, in that case, must be afisumed to run on 

 ■well bey(md its apparent terniinati<in on the costa. At the point where R2+3 

 ends up, this stnmg costal vein broadi ns out a little to meet it, and then runs 

 strongly on for aboul Iwo-thirds of the distance between the two branches of 

 Rs, where it ends. 



