84 S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 



urea is insignificant; the vein runs parallel to the preceding, forks a little way beyond it, 

 the branches again bifurcating once or twice, all in a longitudinal way and closely approx- 

 imated, so that at the extremity of the inner margin the area only covers a very limited 

 space. The anal and internomedian areas together cover almost the entire inner margin, 

 are very broad opposite the middle of the former, where they occupy considerably more 

 than half the breadth of the wing, and rapidly and regularly diminish in width ; the anal 

 furrow is very strongly arcuate, rather distinctly impressed, and terminates at or a little 

 beyond the end of the first third of the inner margin ; there are six or seven simple or 

 forked branches of the internomedian vein, nearly all of which curve a little outward as 

 they approach the margin, and are more longitudinal toward the apex than toward the 

 base. The veins of the anal area are five or six in number, more frequent toward the anal 

 angle, nearly straight and oblique, and simple ; excepting that next the anal furrow, which 

 is arcuate, and emits two or three inferior branches, nearly parallel to the other veins. 



The wings are peculiar for the backward sweep of the scapular vein, so that the entire 

 apex is included in the area of this vein ; the two species differ very much in the proportion 

 of the length to the breadth, one being remarkably stout, the other a little more than 

 usually slender. 



Besides front wings, one of the species referred to this genus, preserves a fragment of 

 the hind wing, and a pronotal shield ; the former consists of the extremity of the costal 

 margin, and simply shows a collection of closely crowded, forked veins, having a somewhat 

 oblique direction, so nearly resembling those of the corresponding portion of the upper 

 wing, by the broken tip of which they lie, as to appear at first sight as a continuation of 

 them ; the pronotal shield is attached to the wing, and is very regularly rounded, scarcely 

 exhibiting the least angulation, somewhat broader than long, with a central circular de- 

 pression. 



This genus differs from Etoblattina in the character of the scapular vein and area, 

 and in the narrow limits of the externomedian area; from Anthracoblattina, Gerablattina, 

 Hermatoblattina, in the brevity of the mediastinal area, and the much greater development 

 of the scapular area; from Progonoblattina in the very different distribution of the 

 branches of the scapular vein, and the far greater extent of the internomedian area ; from 

 Oryctoblattina in the character or position of every area in the wing ; and from Petroblat- 

 tina in the distribution of the veins of the internomedian area and its slight importance. 



The genus is confined to America, and is the only one of this group which has no Euro- 

 pean representatives. 



Archimylacris acadicum. PI. G, figs. 8, 14. 



Archimulacris acadicus Scudd., Daws. Acad. Geol., 2d ed., 388, fig. 153 ; — lb., Amer. Nat., 



i, 630, pi. 16, fig. 2 ; — lb., Geol. Mag., v, 177. 



Fore wing. The shape of the wing cannot be definitely determined from its imperfec- 

 tion ; the costal margin, however, is very regularly and strongly convex, and all the veins 

 are arcuate, arising apparently from about the middle of the wing. The mediastinal vein 

 is subparallel to the costal margin, but a little less arcuate than it, probably occupies about 

 one-fourth its width, and terminates at about the end of the middle fifth of the wing; it 



