28 



FOSSIL INSECTS OF THE BRITISH COAL MEASURES. 



Horizon and Locality. — -Middle Coal Measures (below the Top Hard Coal); 

 Shipley Manor Claypit, Ilkeston, Derbyshire. 



Specific Characters. — Radial sector reaching the inner half of the wing-tip. 

 Outer branch of median four or five times divided, inner branch simpler and 

 forked. Cubitus dividing low down, the outer branch the stronger, and each 

 doubly forked. Anal veins one or two in number, alternately branched. 



Description. — The species is founded on a wing-fragment, the apex, a portion 

 of the inner margin, and the base being incomplete. The total length is 84 mm.. 

 the width 33 mm. The complete wing must have had a length of at least 100 mm., 

 and a width of 35 — 40 mm. The whole insect had in all probability a span of 

 wing measuring 25"5 cm. (10 in. or more). 



The outer third of the wing is differentiated from the rest by its uniform and 

 gentle convexity, and by the character of the costa, subcosta, radius, and median 

 veins, which pass outwards towards the wing-apex in straight lines, and show no 

 trace of divisions until well beyond the middle of the wing, contrasting strongly 





Fig. \..— Orthocosta splendens, Bolton; restoration of wing, showing portion preserved and the 

 character of the interstitial neuration, na e Middle Coal Measures (below the Top 

 Hard Coal) j Shipley Manor Claypit, Ilkeston, Derbyshire. Moysey Collection, Mus Pract. Geol. 

 30,222 and 30,223). 



with the areas occupied by the marginal divisions of the median, cubital and anal 

 veins. The inner two-thirds of the wing is marked by deep furrows, in which lie 

 the marginal branches of the median vein, and the whole of the cubital and anal 

 veins. The areas between any two veins in this region are markedly convex. 

 The differences in character of the outer and inner portions of the wing are empha- 

 sised by a line of fracture which fairly accurately separates the two. Its occur- 

 rence suggests that it has followed a uatural line of weakness, the more delicate 

 inner part of the wing breaking awaj from the outer stronger portion. 



The costa, subcosta, radius and median are all well-developed veins, .stout in 

 structure and standing out in relief. The first three retain this evidence of 

 strength over two-thirds of their length, the median vein showing signs of 

 attenuation beyond the proximal third. 



The general structure of the wing indicate- considerable powers of flight. 

 The outer margin, of which only a port ion is preserved, appears as a stout, slightly 

 elevated and well-rounded ridge. 



The subcosta agrees in general character with the costal remnant, and is 



