180 S. II. SCUDDER ON THE WINGS OF SOME FOSSIL NEUROPTERA 



stem, which runs equidistant from it to the outer border, or reunites with the main stem, 

 sending off continually branches parallel to the first-mentioned branch. These latter 

 branches are either united by frequent or infrequent cross-liars, or they may fork to an in- 

 definite extent, or only near the border, or the space between the first branch and its 

 branchlet, parallel to the main nervure, may be filled with a net-work of veins. The main 

 stem and the branch parallel to it may be united by few or many cross-veins. The v. ex- 

 terno-media may be either perfectly simple (Nemoptera, Acanthaclisis), or it may fork once 

 from near where it leaves its close conjunction with the previous nervure, generally diverg- 

 ing narrowly, and have its forks continually united by cross-veins, while the spaces on either 

 side are differently characterized, or in some other way show more or less distinction from 

 the surrounding spaces, or it may so fork without such distinction (Drepanopteryx, Chrys- 

 opa, Polystoechotes), or it may fork farther from the base, and refork once or twice (Sis- 

 yra) ; at all events, it occupies quite an unimportant part, Chrysopa alone excepted. The 

 v. interno-media extends generally some little distance from the base before forking, though 

 sometimes it forks quite near to it, and generally occupies considerable space, in which the 

 character of venation is similar in nearly every case to that seen in the space occupied 

 by the v. scapularis. In Drepanopteryx, Nemoptera, Ascalaphus, and Acanthaclisis, they 

 are especially prominent, while in Chrysopa the large extent of the v. externo-media seems 

 to be balanced by the slight development of this vein, for it simply forks once, curving 

 downwards and meeting the border. The branches proceed downwards toward the border 

 mainly parallel to one another, and thrown off from the upper branch of the original 

 fork, which itself runs in close proximity to the v. externo-media. The v. analis generally 

 occupies but a small space, forking at least once, sometimes its forks uniting and from their 

 union sending forth new forks. In one instance at least (Polystoechotes) it occupies a 

 larger space, and forks indefinitely. 



In that abnormal genus of Hemerobina, Nemoptera, where the hind wing is reduced to 

 a long, ribbon-like appendage, the v. externo-media alone is wanting ; all the rest are per- 

 fectly simple and parallel. 



CoNIOPTERYGIDjE. 



In this family the venation is very simple. The v. marginalia (if it exists) is continuous. 

 The v. mediastina is simple, parallel to v. marginalia, and extends to the tip of the wing. The v. 

 scaptdaris forks near the middle of the basal half of the wing, the lower branch forking widely 

 shortly before it reaches the lower angle, the upper continuing parallel to the v. mediastina, 

 sending out a branch sub-parallel to the lower branch, which forks widely before reaching 

 the border. The v. externo-media is simple, runs sub-parallel to the r. scapularis, and is united 

 to it by the only cross-vein that exists in the wing, just anterior to the branching of the 

 former. The v. interno-media forks at its origin, the forks continuing sub-parallel to the for- 

 mer. The v. analis exists only on the border, if at all. 



PiHArHIDIIDJE. 



The v. marginalis is continuous. The v. mediastina runs parallel to the former and strikes 

 it in the apical half of the wing. The v. scapularis runs parallel also to the v. marginalis, and 

 terminates at the tip of the wing. It sends off a widely diverging branch near the middle 

 of the wing, which forks widely before it has passed half way to the margin, the upper fork 



