ARCHIMYLACRIS HASTATA. 105 



united with it, rapidly diverging to the distal part of the inner margin. Four 

 branches are given off on the outer side, the first forking before the broken edge 

 of the wing is reached. The remaining three probably forked also on the missing 

 part of the wing-apex. The subdivisions of the median occupy the inner half of 

 the wing-apex, and the apex itself. 



The regularity of arrangement of the minor veins is a marked feature of this 

 wing, and lends colour to our supposition. 



The cubitus gradually diverges from the median along the whole of its course. 

 Ten branches are given off on the inner side, the first only forking. 



The anal area is sharply marked off from the rest of the wing by a deep anal 

 groove, the anal area being elevated and somewhat convex in outline. Ten to 

 eleven anal veins can be distinguished, the marginal ones being very short and 

 feeble. 



The interstitial neuration consists of close, strong, transverse nervures so 

 numerous as to give the wing-surface a finely corrugated appearance. 



The tegminawere apparently of great strength, the unusual development of the 

 transverse nervures adding to the rigidity, while the presence of an oblique ridge 

 served to support and strengthen the radius, median and cubitus at their base, and 

 a similar ridge gave support to the whole of the anal area. 



Affinities. In 1911 (Joe. cit.) I gave reasons for regarding this species as an 

 Archimylacrid, comparing it with A: spectabilis, Goldfuss, and A. venusta. More 

 recently, Dr. Pruvost ('Ann. Soc. Geol. Nord,' vol. xli, p. 335, pi. ix, figs. 4 4 a, 

 1912) has expressed the opinion that it is so nearly like A. belgica,, Handlirsch, and 

 a specimen he has himself described from the roof of the Alfred Vein, Lievin, 

 Northern France, as to be referable to that species. An examination of the figures 

 published by Handlirsch and Pruvost does not support this view. Archimylacris 

 belgica was founded by Handlirsch (' Mem. Mus. Roy. Hist. Nat. Belg.,' vol. iii, 

 p. 12, pi. iv, figs. 1718, 1906) on a wing in the Brussels Museum, from the West- 

 phalian or Middle Upper Carboniferous of Jemappes, Belgium. It was afterwards 

 transferred by him to a new genus, Parelthoblatta (' Die Fossilen Insekten,' p. 184, 

 pi. xviii, fig. 54, 1906). This new genus is not accepted by Pruvost, who considers 

 that it is founded chiefly on the pectinate character of the first branch of the radius. 

 He therefore replaces the species in the genus Archimylacris, and refers his ow r n 

 specimen to the same genus and species. With this conclusion I cannot agree. 

 Handlirsch's species is characterised not only by the pectinate character of the 

 first branch of the radius, but (and much more important) by the presence of a 

 meshwork of interstitial neuration between the radius, median and cubitus. This 

 latter feature clearly separates not only the French specimen from Handlirsch's 

 genus Parelthoblatta, and therefore from P. belgica, but the British specimen also ; 

 for in both the interstitial neuration consists wholly of a close series of straight 

 cross-nervures, with not the slightest trace of the development of a network. 

 14 



