168 TERTIARY INS KITS OF NORTH AMERICA. 



the marginal nervnles are sometimes simple and straight, sometimes broadly 

 forked, and differ on opposite wing's. The vein below the lower cubital, 

 called postcostal bv McLachlan, terminates abruptly on the hinder margin, 

 opposite the origin of the sector of the radius. 



Length of fore wings, 15.7;")' ..... : breadth, . r ).4""" : length of hind wings. 

 15 mm ; breadth, 4.2 mm . 



The four wings of this specimen are so overlaid by one another as to 

 make a medley of veins which are very difficult to disentangle and inter- 

 pret. It was kindly photographed for me by Mr. Samuel Wells, of I'mston; 

 the lines of each wing on the photograph were then traced separately, and 

 from these tracings the drawings on the plate were made; these 1 believe 

 to be true representations of the wings with the exception of the double 

 cubital cell of both wings and the cross-veins of the costal area of the hind 

 wing, which are not shown : the lower half of each wing, however, is more 

 liable to misinterpretation than the upper. 



Florissant. One specimen, Nos. 1798 and 7340. 



2. TRIBOCHRYSA gen. nov. (rp//?a>, z 



This genus, clearly allied to Palgeochrysa, and with it apparently a 

 forerunner of Hypochrysa, is represented by several species in the Amer- 

 ican Tertiaries, which are uncommonly well preserved, though the wings 

 are the only parts which are [(resent on all the specimens; and it is there- 

 fore mainly upon these that the genus is founded The head is nearly 

 twice as broad as long, the front protuberant, rounded, and entire, the basal 

 joint of the antenna 1 stout, bulbous, scarcely longer than broad, twice the 

 diameter of the stalk, the latter nearly as long as or even longer than the 

 body, slender, delicate! v tapering, composed of simple, cylindrical, appar- 

 ently naked joints twice as long as broad. The thorax is stout, the protho- 

 rax broader than long, tapering anteriorly, otherwise subquadrate. The 

 legs are slender. The wings extend far beyond the body, and are of the 

 same form as in ('hrvsopa, the tip rounded or faintly snbacuniinate ; in 

 neuration tliev resemble closely those of Paheochrysa, but differ from it in 

 one striking feature, and in this approach more modern types like Not ho 

 chrysa. In Palseochrysa the upper cubital vein runs in a slightly zigzag 

 course through the middle of the wing in a regular, gentle curve nearly 

 equidistant from the costal and inner margin, and terminates at the apex of 

 the wings, no transverse series of gradate veinlets lying between it and the 



