114 FOSSIL INSECTS OF THE BRITISH COAL MEASURES. 



times as long as wide. The structure is well preserved, and the principal veins 

 and their subdivisions are in relief. 



The costal margin is thickened, strongly convex, and well rounded at the base. 

 The costal area is unusually broad and strap-shaped, extending over two-thirds of 

 the costal margin. The basal portion of the costal area is smooth, and not crossed 

 by branches of the subcosta. 



The subcosta is thin, elevated basally, and somewhat crenulated, doubtless 

 owing to post-mortem change or pressure. The subcosta is parallel with the 

 costal margin over more than one-half the length of the wing, and gives off six- 

 oblique branches to the margin. Three of these branches are forked. 



The radius passes out to the apex of the wing, giving off six outer branches, 

 the first forking once, and the second twice before reaching the margin. The 



Fio. 36. — Phyloblatta sulcata (Bolton) ; diagram of the venation, and restored outline of fore-wing, two- 

 and-a-half times natural size. — Upper Coal Measures (Gwernau Level of the Mynyddislwyn Vein) ; 

 near Maes-y-cwmmer, Monmouthshire. Mus. Ptact. Geol. (nos. 24504, 24505), Numbering of 

 veins as in Text-figure 33, p. 104. 



remaining branches are undivided. The radius and subcosta together occupy a 

 little less than half the total wing-area. 



The median vein is convex outwards in its basal half, and then bends inwards 

 to the junction of the inner and apical margins. It gives off three long, outward, 

 undivided branches, all of which are parallel with the main stem of the radius. 

 Basally, the median curves sharply inwards and unites with the cubitus, the two 

 veins having a very short common stem. 



The cubitus is the largest and most important vein in the wing, although but 

 faintly outlined at the base, where its union with the median is nevertheless quite 

 clear. It gives off seven inwardly directed branches, the third only forking. On 

 its outward side two branches are given off. 



The anal furrow is represented by a strong ridge, and is therefore a well- 

 marked groove on the dorsal surface of the wing. The anal area is laro-e 

 extending at least one-third the length of the inner margin, and crossed bv five 



