124 S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 



oblique, simple or forked cross-veins. The scapular vein, contiguous to, perhaps united 

 with, the externomedian in the basal part of the wing, is of small importance, emitting 

 in the apical half of the wing only two or three branches, which are superior, simple, or 

 furcate, and terminate on the costal margin, the whole tip (in one species at least, and 

 perhaps in both) belonging to the externomedian vein. The externomedian vein is the 

 most peculiar in the wing ; as soon as it is free from the common basal union of all the 

 veins, it curves strongly backward to about the middle of the inner margin, in close prox- 

 imity to the internomedian vein ; and from its superior, now outer, surface emits a large 

 number of parallel, forking veins, which terminate on the apex and outer half of the inner 

 margin of the wing. The combined internomedian and anal areas are very broad at base, 

 occupying fully two-thirds the breadth of the wing, and retain their breadth for some dis- 

 tance and then narrow with excessive rapidity, dividing about equally between them the 

 common space ; the branches of the internomedian vein are five or six in number, straight 

 or arcuate, simple or occasionall\ r forked. The anal furrow is very arcuate, not very prom- 

 inent, and terminates near the middle of the basal half of the wing; the anal veins are fre- 

 quent, arcuate, but not so strongly as the furrow, and simple or occasionally forked. Only 

 upper wings are known. 



The wings are stouter than usual, although they are not sufficiently well preserved to 

 give any more definite statement than that they are, on the average, stouter than any 

 other, excepting probably Hermatoblattina, and possibly Anthracoblattina. 



This genus is remarkable for the close union of the veins at the base, and for the very 

 strong curvature of the externomedian vein, by which it resembles somewhat the anal 

 furrow, and for the contrasted longitudinality of the branches which spring from it. In 

 these particulars it differs strikingly from every other genus, and can be confounded with 

 none of them. 



Only two species have been described, one of which is European, and the other, known 

 only by a very small fragment of a wing, American ; they are both of rather small size. 



Petrablattina gracilis. PI. 4, fig. 4. 



Blattina gracilis Gold., Palaeontogr., iv, 23, taf. 3, figs. 3, 3 a ; — lb., Foss. Ins. Saarbr., 7, 

 taf. 1, figs. 3, 3 a ; — lb., Faun, saraep. foss., ii, 20, 27-28, 51, taf. 2, fig. l a ; — Heer, Vier- 

 telj. naturf. Gesellsch. Zurich, ix, 288 ; — Gein., Geol. Steink. Deutschl., 150. 



Blatta gracilis Gieb., Ins. Vorw., 321. 



Fore wing. The wing is of a regular elliptical form, broadest in the middle, tapering 

 more rapidly toward the apex than toward the base, both costal and inner margin equally 

 and rather gently convex, the tip a little pointed, but well rounded. The veins all origin- 

 ate above the middle of the upper half of the base, but, excepting the anal furrow, have no 

 basal curve. The mediastinal vein runs subparallel to the costal margin, but in a straight 

 line, nearly to the middle of the wing, and then curves very gradually to the border, which 

 it reaches a little before the end of the middle third of the wing ; the area is a little less 

 than a fourth the width of the wing ; its basal half is filled with closely crowded, arcuate, 

 oblique, simple branches, the apical half with similarly crowded and arcuate, longitudinally 

 oblique, much longer, and usually forked branches. The scapular, externomedian, and in- 

 ternomedian veins evidently spring from a single stem, according to Goldenberg ; the in- 



