S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 119 



This genus is readily separated from all the preceding by the much greater common 

 expanse of the scapular and externomedian veins, and the unimportance of the interno- 

 median area ; indeed, in these particulars it surpasses any of the ancient genera of cock- 

 roaches. From Oryctoblattina it is readily separated by the brevity of the mediastinal 

 area, and by the approximation of all the veins in the basal half of the wing. The totally 

 different character of the externomedian vein distinguishes it from Petrablattina, although 

 it approaches that genus in the abundance of the neuration. 



The two species, which differ widely from each other, are European ; one of them is a large 

 species, the other rather small. 



Progonoblattina helvetica. PI. 3, fig. 10. 



Blattina helvetica Heer, Viertelj. naturf. Gesellsch. Zurich, ix, 287, 291-93, pi., fig. 1 ; — 

 lb., Urw. Schweiz., 592, note ; — lb., Monde prim, suisse, 22, fig. 16c al> ; — Gold., Faun. 

 saraep. foss., ii, 19. 



Blatta helvetica Heer, Prim, world Switz., i, 20, fig. 16c ab . 



Fore wing. The wing is pretty regularly elongate-obovate, the costal and inner margins 

 about equally and considerably convex, the apex tapering but well rounded. The base of 

 the wing is broken, especially next the margins, so that the mediastinal vein can be traced 

 only a short distance ; here it runs near and parallel to the margin, and by a gentle curve 

 strikes it at the end of the middle fifth of the wing ; the width of the area is less than a sixth 

 that of the wing, and in the portion preserved only a couple of branches are seen, widely 

 separated at their origin, simple and arcuate, but brought near together by their unusual 

 longitudinality, so that it is doubtful if there are more than five or six branches to the vein. 

 The following areas, as Heer has pointed out, are difficult to separate, from the fact that 

 the base of the wing is lost, and they all divide so early as to exhibit at the edge of the 

 fragment, very near the base, no less than eight nervules between the mediastinal vein 

 and the anal furrow. It would, however, present a structure so abnormal were any but 

 the nervure next the anal furrow to belong to the internomedian vein, that it seems almost 

 certain that we must divide seven of them between the scapular and externomedian veins ; 

 the three lower of these have an oblique course at the base, and are separated by an 

 unusual width from the upper four, which in their turn have a longitudinal course ; and 

 these two bundles of nervules we may consider as belonging to the externomedian and 

 scapular veins respectively. On this assumption the scapular vein is longitudinal and 

 nearly straight, and terminates just above the extreme tip of the wing ; it has six longi- 

 tudinal branches, three of which originate within the basal quarter, two near the middle 

 and one next the tip of the wing ; the first and last are simple, the others simply, the 

 middle one doubly forked ; the basal branches curve very gently upward toward their 

 tip, but the others are wholly horizontal. The externomedian vein is more difficult to 

 define ; the three veins with which it starts from the base of the fragment are very similar 

 in character, and being perfectly parallel next the edge (which must lie within the basal 

 fifth or sixth of the wing) it is not clear which should be looked upon as the main stem ; 

 but the main stem may be said to break close to the base into three branches which run 

 close together toward the middle of the outer half of the inner edge of the wing ; omitting 

 the upper branch of the upper vein, each of these three stems links at or just beyond the 

 end of the basal third of the wing, and each of these forks again divides at irregular 



