30 



TYPE : Mesochorista proavita, sp. nov. 



OBS. : A genus very closely allied to T ceniochorista (Recent, 

 Brisbane). 



MESOCHORISTA PROAVITA, sp. nov. 

 Plate 2, fig. 2. 



The specimen is clearly a fore wing. Here and there, in certain 

 lights, very faint impressions of cross-veins are observed which 

 are not shown in the drawings. Between the basal cross-vein and 

 the short distal branch of Sc, three weak cross-veins are observed 

 close together. The most interesting fact about this fossil is its close 

 resemblance to the wing of T ' ceniochorista pallida, Esben-Petersen, 

 a very rare Panorpid known only from Brisbane, where it appears 

 to have an aquatic or semi-aquatic existence. A comparison of the 

 two wings brings out the folio Aviiig points : The two short cross- 

 veins connecting C with Sc are present also in T ceniochorista, in 

 the same positions. The more distal one is also oblique, as in the 

 fossil, but the curve of Sc distad from it is not so marked. In Tcenio- 

 chorifita there are also the three other weakly formed cross-veins 

 close together, midway between the two. 



All Panorpids have a number of short cross-veins between the 

 main branches at intervals. In T ceniocliorista these are formed of 

 weak colourless chitin, little thicker than the membrane of the wing 

 itself. They are not easy to see, unless the wing be held up to the 

 light. It could scarcely be expected that these cross-veins would be 

 preserved in the fossil wing. In view of the close correspondence 

 in all other points, we may be fairly sure that they were actually 

 present. The only one that can be definitely detected is a rather 

 strong cross-vein descending upon Cu from the first dichotomy of 

 M ; only the upper half of this is preserved, T ceniochorista has this 

 cross- vein present and more strongly formed than the others. 



The radius and radial sector appear to be almost exactly alike 

 in the two forms. In the media, the only difference is that in T cenio- 

 chorista only the most posterior of the four stems formed by the 

 second brandling of the upper branch of M is again branched ; i.e., 

 the lower or posterior arm of the uppermost distal fork is absent, 

 and only one vein runs to the wing border there instead of two. 

 The correspondence between the cubital and anal regions of the wing 

 in the two genera appears to be exact. 



We may say definitely that, assuming the presence of the cross- 

 veins already discussed in Mesochorista, the latter would become 

 Teeniochorista by (1) a slight lengthening of the wing, (2) the loss of 



