BOLTONITES RADSTOCKENSIS. 143 



agreeing exactly with what obtains in the same part of the wing in Meganeura 

 niont/i. It is an indication of the rapid inward curvature which takes place a little 

 further out, and of the presence in the complete wing of the wide distal area 

 occupied by the many branches of the radius and the median. 



Close to the basal broken end of the cubitus a strong oblique inward vein is 

 given off, which reaches the anal vein, and fuses Avith it. At the time when I first 

 described this wing I wrote as follows : " It has the appearance of an important 

 commissure between the cubitus and the anal, or of a posterior branch of the 

 former which has fused with the latter." Since then, Dr. R. J. Tillyard has 

 published the results of his studies on recent dragon-flies (' The Biology of 

 Dragon-flies,' Cambridge University Press, 1917), in which he notes our discovery 

 of this oblique vein. He recognises it as an anal-cubital vein which he had 

 previously (' Proc. Linn. Soc., N.S.W.,' vol. xxxix, pp. 163 216,' 1914) 

 described as indicating the point where the true anal vein diverges from the 

 cubitus. He concludes (op. cit., p. 305) : " Hence it would appear that Cu (cubitus) 

 and A (anal) were fused basally as in all recent forms. Thus the gap between 

 Protodonata and Odonata is being gradually lessened until to-day we may almost 

 certainly see in the Meganeuridaa the giant relatives of the direct ancestors of 

 some at least of our recent families." 



Beyond this anal-cubitus vein the cubitus is joined to the anal by a system of 

 parallel slightly curved branches, similar in character to those which unite the 

 sub-costa and the costa. No fewer than twenty-five of these branches can be 

 distinguished. Basally to the anal-cubital vein are two transverse branches, a little 

 more curved than the rest. As in the costa and sub-costa, a median line of 

 tubercular ornament is present. 



The anal vein is strongly marked, and its course is much similar to that of the 

 cubitus, but the second inward flexure is less marked, so that the two veins are 

 closer together in the middle of their length, and more widely separated basally. 

 The anal gives origin, along the whole length of its hinder margin, to a series of 

 branches, which arise at slightly increasing intervals, being closest basally, and 

 most widely separated between the twelfth and thirteenth branches, beyond which 

 the interspaces narrow again to the fifteenth branch. The basal branches pass in 

 straight or slightly oblique lines inwards to the wing-margin. Further out they 

 become curved, with the convexity outwards. The twelfth branch is a strong and 

 important vein, sweeping in a powerful double curve distally, and inwardly to the 

 wing-margin. It corresponds in position to Brongniart's " vein X." Beyond it 

 are the remains of three feebler branches, which bend in simple curves to the 

 margin. 



The spaces between the anal branches are divided up into a series of quad- 

 rangular areas or cellules, by a great series of secondary branches, arising at 

 right-angles. The twelfth dorsal branch stands out from the rest by reason of its 



