134 TERTIARY IXSECTS OF NORTH AMERICA. 



PODAGRION ABORTIVUM. 



PI. 6, Figs. 7, S. 

 Podagrion abortivum Scudtl., Bull. U. S. Geol. Geogr. Snrv. Terr., IV, 775-776 (1878). 



The specimen represents the apical part of a wing with fragments of 

 the middle portion. The pterostigma is a little more than twice as long as 

 broad, and, although less oblique on the inner than on the outer side, yet 

 lies at an angle of forty-five degrees with the costal edge, and is therefore 

 more oblique than usual in Podagrion ; its outer side is arcuate as well as 

 very oblique, but in its entire extent the pterostigma scarcely surmounts two 

 cellules ; the outer side is much thicker than the inner, and thickens below 

 as it passes gradually into the lower border, which, like the costal, is much 

 thickened, and appears the more so from being independent of, although in 

 conjunction with, tlie median nervure. Beyond the pterostigma the ultra- 

 nodal approaches the principal nervure very closely, so that they are only 

 half as far apart at the margin as below the pterostigma ; there are two sup- 

 plementary sectors, one between the ultranodal and the nodal, arising below 

 the outer half of the ptei'ostigma, the other between the nodal and subnodal, 

 arising slightly farther back ; both of these supplementary sectors are 

 straight, but the nodal is slightly undulated after the origin of the supple- 

 mentary sectors ; all the other veins, excepting the extreme tip of the prin- 

 cipal, are straight, and the reticulation tetragonal. The wing appears to be 

 hyaline throughout, the pterostigma very slightly infumated, the nervures 

 fusco-castaneous, those about the pterostigma deepening nearly to black. 

 Apically the wing is well rounded, its apex falling in the middle and not 

 at all produced. A species is indicated of about the size of P. raacropus Sel. 



Length of pterostigma along costal edge, 1.5™™; of same from inner 

 lower angle to outer upper angle, 2.1™™; breadth of pterostigma, 0.65™™; 

 of wing in middle of apical half, 5.5™™. 



Green River. One specimen, No. 4169. 



3. LITHAGRION gen. nov. {XWo?, Agrion). 



Subnodal sector originating from the nodus, the median a little more 

 than one cellule previous to it, the nodal at a little less than one-third the 

 distance from the nodus to the pterostigma ; the latter is stout, dilated, sur- 

 mounts about five cellules, it^ inner border a little oblique, its outer sliglitly 



