ARCELEOPTILUS INGENS. 



75 



and below the interspaces mentioned, seem rather closely crowded, and much 

 more curved, sweeping downward, while the upper veins show little tendency to 

 turn from a longitudinal course." 



The great apparent width of the costa is caused by the formation of an 

 expanded chitinous bar along its outer margin, the free edge bearing the spines 

 described \)j Scudder. The costn, with its chitinous bar, the subcosta and 

 the radius are so broad as to appear strap-like, are widely separated, and the 

 intervening areas are crossed by equally strong nervures. The costa can be 

 distinguished on the cast from the frontal bar and appears as a narrow 

 rounded vein. 



The subcosta is a very broad vein, crossed by oblique striae which are directed 

 outward from the upper edge of the vein. A broad interval (9 mm.) separates 

 it from the costa, the area being crossed by stout, slightly oblique, transverse 

 nervures. The general direction of the subcosta is such that it must have reached 

 the margin of the wing near the apex. At the base it is much enlarged, the 



Fig. 23. — Archaeoptilus ingens, Scudder; diagram of whole wing from Scudder's original restoration, one-quarter 

 ^natural size. — Upper Coal Measures ; near Chesterfield, Derbyshire. Brit. Mus. (no. I. 3997). 



enlargement probably indicating the attachment to the body of the insect. The 

 expanded inner portion of the base is fused with the equally expanded base 

 of the radius. 



The radius diverges from the subcosta in its outward course, and is even more 

 enlarged than the subcosta. It is connected with the latter by a series of thirteen 

 transverse nervures in the wing-fragment. Most of these are slightly convex, 

 and two are united by lateral branching. 



The median vein was apparently closely apposed to, or united with the base 

 of the radius, and is much less robust than the latter, the intervening area being 

 narrow, and crossed by short, thin, straight, transverse nervures which do not 

 appear to continue into the base of 'the wing. The cubitus is not so readily- 

 distinguishable, and diverges sharply inwards towards the inner margin. The 

 anal veins are 4 — 5 in number, and are strongly curved inwards, occupying 

 not more than one-fifth of the inner margin of the wing. The first three may 

 have been united at their base. The wing is marked by a series of folds along 

 the lines of the principal veins. 



Affinities. — This remarkable wing-fragment has caused considerable conjecture 

 as to its true character and relationship. Scudder in his second note (loc. cif., 



