S. H. SCUDDER ON PALAEOZOIC COCKROACHES. 47 



McDonough Co., Illinois, in the roof shales of coal No. 2 of the Illinois Survey, and by 

 him communicated to me. Lower coal measures of Illinois. 



Mylacris Mansfieldii nov. sp. PL 5, fig. 15. 



Fore winy. The base of the wing is broken, but the part preserved shows an oval 

 outline, with similarly arcuate costal and inner margins and a somewhat pointed tip, the 

 extremity of which is rounded; the tapering of the wing includes all the apical half. The 

 mediastinal area is very large, occupying fully one-half the breadth of the wing at the base 

 and covering about two-thirds of the costal margin; the veins of its outer half (the base 

 is broken in the specimen) are very long, very slightly arcuate, slightly radiate but sub- 

 parallel, simple or deeply forked and closely crowded, and the limitation of the area next 

 the scapular vein is straight. The scapular vein runs nearly parallel to the costal margin, 

 at least in the middle of its course, but in the apical third becomes longitudinal, passing 

 down the wing scarcely above its middle line ; it commences to divide near the base of the 

 fragment, and probably a little before the end of the basal third of the wing, and emits five 

 branches at unequal distances apart, one or two of which are singly or doubly forked, and 

 all run parallel to the outer mediastinal branches; the vein terminates at the tip of the 

 wing and so the area occupies on the margin the apical third of the costal border. The 

 externomedian vein has a slightly arcuate course, which, contrary to what is customary, 

 runs subparallel to the inner margin and, commencing to divide a little before the middle 

 of the wing, emits, near together, three inferior branches which are long, simple or forked 

 and longitudinal, the basal ones more or less arcuate in the same sense as the main vein; 

 as these branches are inferior, the interspace between the scapular and externomedian 

 veins (running almost exactly down the middle of the wing) is marked by the divergence 

 of the opposing nervules. The internomedian vein is broadly arcuate and terminates on 

 the inner border considerably nearer the tip than the mediastinal vein; it emits three 

 branches, the apical one compound, the others more or less deeply forked, so that this area 

 is as crowded with veins as the others. The anal furrow is lightly impressed, scarcely 

 arcuate in its apical half, and terminates at the edge of the fragment, probably at about 

 the end of the basal half of the wing. 



The species is a tolerably large one, the largest of the genus, the fragment of the wing 

 measuring 24 mm. in length and 13 mm. in breadth; probably the entire length was about 

 30 mm. and the breadth to the length as 1 : 2.3. The wing is a Left one and the upper 

 surface is exposed ; the veins are lightly impressed throughout and uniformly and rather 

 closely crowded; the surface is nearly smooth, but with care a delicate wrinkling of ob- 

 scure transverse lines can be made out. 



The wing is peculiar for its tapering oval form and the inferior origin of the externo- 

 median branches, which distinguishes it at once from every other species of this genus. 



The single specimen found was sent to me by Mr. I. F. Mansfield and by him obtained 

 at Cannelton, Beaver Co., Penn., in dark sandy shale immediately under the vein of cannel 

 coal known as vein C of Professor Lesley. Lower coal measures of Pennsylvania. 



