346 SAMUEL II. SC'UDDER ON THE 



Megathentomum Scudder. 



This genus has certain relations to the preceding, since most of the branches, which are 

 apically formed, must, in most instances, to judge of their direction by the only fragments 

 which are known, have originally parted from the main stem very near the base. The 

 branches are, however, very few in number, and the wing remarkably broad, rounded and 

 large, the main scapular vein branching only near the tip, and the vein there bent 

 upward as if it were a superior branch and the first branch the main vein. Two species are 

 known, one from this country and one from Germany. 



Megathentomum pustulatum. PI. 32. figs. 1, 9, 10. 



Megathentomum pustulatum Scudd., Proc. Bost. Soc. Nat. Hist., xi, 401-402 ; 1b., Geol. 

 Surv. 111., in, 570, fig. 7. 



The original specimen (fig. 1) is the best that has been found, so far as I know, but sev- 

 eral others have been discovered, one of wbich is figured here. Tlie wing was exceedingly 

 broad, indeed, probably more than half as broad as long. It was broadest beyond the mid- 

 dle and subtriangular in shape, though the outer margin was fully rounded. The medias- 

 tinal vein was long, terminating shortly before the declivent termination of the straight 

 costa, and emitting several very oblique and nearly straight branches to it. The scapular 

 vein, parallel to the latter, first branches near the tip of the latter, sending out one or two 

 simple or forked branches which support the upper tip of the wing. The externomedian 

 vein occupies the middle third of the wing, and occupies the largest area, dividing into 

 three branches near the base of the wing, each of which forks singly and rather widely near 

 the border, and at varving distances from it. The internomedian vein divides more than 

 once and supports the lower outer angle of the wing. 



In this specimen there are six larger, round or squarish, discolored spots, the surfaces 

 irregularly elevated or blistered ; four of them form a bent row in the middle of the outer 

 half of the wing, the upper three spots being nearly straight and the lower one turned 

 inward at a little more than a right angle ; the uppermost spot occurs in the scapular-exter- 

 nomedian interspace; the others follow in succeeding interspaces. The two other large 

 spots are found in the same interspace with the upper two of the inner row and are situ- 

 ated about half way between them and the border. There are also many smaller spots, often 

 deeper in tint and not elevated, which appear to be less regularly distributed ; they arc 

 usually round but sometimes oval or transversely elongated ; there are three at equal dis- 

 tances from one another in the lower interspaces formed by the branches of the scapular 

 vein, another occurs just within and above the inner of the^e three, and one in the angle of 

 the last branch of the scapular vein; there are'two between the forks of each of the upper 

 branches of the externomedian vein, and one near the margin between these two forks ; 

 two larger and elongated spots occur in the same interspace with the lowest of the larger 

 spots, at equal distances on either side of it, and the outer close to the margin of the wing: 

 three equidistant ones are seen in the fork of the upper internomedian branch, one near 

 the middle of the hind border, and finally two faint one-: in the middle of the wing situated 

 beneath and against the upper branches of the externomedian vein. 



