CLASSIFICATION OF PALEOZOIC INSECTS. 339 



branch which arises before, generally far before, the middle of the wing, and runs sub-par- 

 allel to the main stem ; from this branch arise a variable number of obliquely longitudinal, 

 simple, or forked offshoots, which generally occupy the whole of the apex of the wing, and 

 sometimes infringe a little upon the lower margin. The externoinedian vein generally 

 extends nearly to the middle of the wing before branching, and then forks more or less 

 abundantly, showing considerable variation in this respect, the nervules sometimes oc- 

 cupying the larger part of the outer half of the inner margin, sometimes reduced to a sin- 

 gle branch or two. The internomedian vein resembles the preceding, although it branches 

 from the the base and is generally more important than the externoinedian vein where the 

 latter is poorly developed, though sometime-! it is simple. The anal veins generally occupy 

 the basal fourth of the inner margin, with a series of simple, or simply forked, sub-paral- 

 lel branches, generally arising close to the base of the main stem. 



This group has been twice described and named by me — once in I860 1 under the name 

 of Hemeristina, when only a single and rather aberrant form was known to me ; and again 

 in 1880 2 under the name of Cronicosialina, when discussing the affinities of one of the 

 Devonian forms. It now appears that not only these, but the series of wings discussed by 

 me in a paper on English paleozoic insects 3 (excepting one, Archaeoptilus, shown to belono- 

 in quite another place) should be brought together from possessing one important charac- 

 ter in common, characteristic of the neuration of most plannipennians to-day, — the exis- 

 tence of a main scapular branch from which a considerable number of inferior offshoots 

 arise and occupy the entire tip of the wing, or even more than that. In modern planni- 

 pennian Neuroptera it is usually more important than here, and the modern groups to 

 which this series of forms bears most resemblance — the series allied to Sialis — differ in 

 that the mediastinal vein impinges on the scapular and not on the costal margin. The 

 ancient group can, indeed, only be looked upon as a generalized plannipennian type, as we 

 have already pointed out in our discussion of the British forms (loc. cit.). 



Other ancient groups, indeed, the Palaeopterina and Xenoneuridae. agree with it in the 

 possession of a single, main scapular branch from which offshoots arise ; but in each of 

 these the offshoots are few in number and importance as compared to what is found in 

 the Hemeristina ; from them it further differs in the point of termination of the mediastinal 

 vein, and the usually far greater importance of the scapular branch ; while from the Palae- 

 opterina it may also be distinguished by the minor importance of the internomedian vein, 

 and from the Xenoneuridae by the more abundant neuration. Gerstaecker has referred 

 Hemeristina positively to the Ephemeridae with which it has no more in common than have 

 the other families here characterized, whose mediastinal vein terminates on the costa. 



Lithomantis Woodward. 



Piothorax with large, dilated, and rounded lateral lobes. Mediastinal vein of front wings 

 running in very close proximity to the border, but farther from it in the middle than at 

 the base of the wing. Internomedian area extensive, occupying the middle third of the 

 lower margin, and fully as important as the externoinedian area. 



1 Mem. Bo?t. Soc. Nat. Hist., [, 190. a Mem. Bost. Soc. Nat. Hist., m, 21.1. 



2 Devon. In?. New Brunsw. 



