416 



TWO FOSSIL INSECT WINGS IN COLLECTION OF MR. ,TOIIN MITCHELL, 



half-way along the costa, where R<- ends. It is certain tliat the hindwiiig of 

 Prosbole had no division into coriura and membrane, and also had no nude, .since 

 neither of (hese specialisations has ever iK-en developed in a hindwing of the 



Te.\t-fig. 2. Prosholf hirsiita Kokeii, hemelytron, after Haudlirsch. (v 2.1). 

 Upper Permiaa, Kama River, Russia. «, node. 



Order. The general resemblance of the venational scheme in the two genera is 

 evident enough, though the number of branching's of Ks and M is ditt'ei'ent. The 

 general arrangement of the system of cross-veins is also similar, though Prosbnle 

 has more of them than Mitchelloneiira. Charactei's shared in common by tlie 

 two wings are: — the short Sc, fused with R, and ending up in a characteristic 

 manner about half-way along the wing, the nearly straight Ki, with cross-veins 

 C(mnecting it with the costa, the general arrangement of Rs, M and Cui with 

 respect to one another, and their lack of branching or cross-veins before half- 

 way along each of their lengths, the form of tlie fork of Ks, in which ^i+i, 

 arches up anteriorly, while R4_|_5runs almost straight on, the form of the fork 

 of Mi + .;and the forking of Cui.. On the other hand. R^ , , does not .ioin up 

 with Ri in Prosbole; Ri^s, has an extra branch; M2 is forked; and M.i , 4, in- 

 stead of being a simple vein, not only forks, but has aji e.xtia fork on M4. 



It seems reasonable to conclude that, if the forewing of Mitch>elloneura were 

 known, it would be sufficiently like that of Prosbole to allow tlie two genera to 

 be pla<'ed within the same family, though not in the same genus. 



MlTCHELLONElRA PKR.MIAN.i, u. sp. (Plate .xx.vv., Hg. 1 : Tc.Kt-fig. 1.) 



II ill (I wing: Total length, 17 mm; greatest breadth of specimen, 7 mm., 

 representing a total width for the (complete wing of about 7.5 mm. 



The s))ecimen is the mould or counterparl of a right wing, a.s is proved 

 by the fact that Ri, Cm and the anal veins are concave, while M is convex in 

 the fossil impression. It rests in a slightly irregular hollow of a piece of hard 

 burnt shale having a conchoidal fracture; the apex is to the left. Text-fig. 1 

 gives a diagram of the wing with the apex turned to the right, and the missing 

 parts restored by the dotted lines. The softne.ss and delicacy of the wing m(^in- 

 brane is indicated by numerous signs of stretching mid rucking present in the 

 fossil. Kxcept in some of the higher Holometabola, furewings having such a 

 delicate structure of the membrane are seldom met with; and, .as this is a wing 

 of considerable size and very strong venation, this condition of the membrane 



