S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 57 



very great; the general coarse of the scapular vein is usually parallel to the costal margin, 

 but without partaking of its generally slight convexity ; beyond the immediate base of the 

 wing therefore its course is nearly straight, sometimes with a gentle sinuosity ; occasionally 

 it is conspicuously sinuous, as in E. labachensis, so that the greatest breadth of the scapular 

 area is double that of the mediastinal ; yet even here the general resemblance and trend of 

 the branches of the two veins may be perfectly kept. The externomedian vein is of 

 moderate importance, occupying always a portion, generally the whole, of the apex of the 

 wing, generally commencing to branch not far from the first divarication of the scapular 

 vein, but in this respect showing great variation ; its branches are not numerous, occasion- 

 ally reduced to two or three, and while longitudinal are yet always superior, so that the 

 equal sinuously curving space between the externomedian and internomedian veins is 

 always marked by divergent branches, very frequently arising exactly one opposite an- 

 other. The internomedian vein originates near the middle of the wing in about half of 

 the species (the first half of the species described below), somewhat above the middle in 

 the other half; usually it is pretty straight beyond the arched base, and does not terminate 

 so near the apex of the wing as does the scapular vein ; but not infrequently it reaches as 

 far as the scapular, or at any rate extends further than it otherwise would by curving 

 outward near the tip, and thus reaching to a greater distance ; there is therefore much 

 difference in the rapidity with which this area narrows, being very rapid in some (as in 

 E. russoma), very gradual in others (as in E. Lesquereuxii) ; its numerous veins are nearly 

 straight ; usually some of them are simple, and they have an obliquity about equal to those 

 of the mediastinal vein, although of course in an opposite sense. The anal furrow is 

 rather more lightly impressed than usual, arcuate and very oblique, generally terminating 

 on the inner margin at about two-fifths the distance from the base ; the veins of the anal 

 area are usually simple or forked near the base, very frequent, subparallel and subequi- 

 distant, generally less arcuate than the anal furrow; in one species, M. mantidioides, they 

 are very irregular. 



Usually the upper wings are moderately slender, from a little less than two and a half to 

 about two and three-quarter times as long as broad ; but a few of the species have wings 

 more than three times as long as broad, and the first two species differ from the others, 

 not only in their unusual breadth, being only a little more than twice as long as 

 broad, but also in other features, such as an unusual breadth (and in E. labachensis an 

 unusual length) of the mediastinal area, the narrowness of the externomedian area, and 

 the extreme longitudinality of its branches; as, however, the form of the wing often 

 appears to differ very considerably in species of the same genus in this group, there is not 

 sufficient ground for the separation of these species from the others even as a section, and 

 the more so as there are several other species, placed in the middle and at the other 

 extremity of the genus, which have quite as broad wings. The general average is scarcely 

 less than two and three-quarter times longer than broad, which is a trifle slenderer than 

 the average of the whole tribe; and it is not a little curious that this is exactly the same 

 proportion as holds in the genus next to this most prolific in species, Gerablattina. 



Besides the front wings, which constitute most of the fragments of this genus preserved, 

 there are two which show the hind wings also; one of these also has the thorax and 

 abdomen, and a third the thorax. The hind wings appear to resemble the front wings 

 closely, and not to be much larger, at least in one of the species ; the thorax in both 



MEMOIRS BOST. SOC. NAT. HIST. VOL. III. 



