136 TERTIARY INSECTS OF NORTH AMERICA. 



The wings are hyaline and are petiolated up to the base of the quad- 

 rilateral or some distance beyond the first postcostal nervule. intranodal 

 sector originating from a cross vein midway between the nodus and the 

 pterostigma, its course regular and not zigzag throughout its extent ; inferior 

 sector of the triangle straight to near its tip, where it bends a little upward, 

 running parallel to the margin and terminating in a cross vein, a little 

 irregular near the tip. Pterostigma dark chocolate brown,' the bordering 

 veins thickened and black ; being broken its form can not be positively 

 stated, but it appears to be nearly four times as long as its median width and 

 considerably expanded on the under surface, probably surmounting four or 

 five cellules ; quadrilateral more than four times its breadth at base, its 

 lower side half as long again as the upper, the outer side very oblique. 

 Nodus rather more than one-third the distance from the base to the ptero- 

 stigma ; sixteen postcubitals. Wings rather slenderer than in L. umbratum. 



Probable length of wing, 33°"" ; breadth, 6.G"" ; distance from nodus to 

 pterostigma, 17°""; from nodus to base. 11.5°""; breadth of wing in middle 

 of petiolated portion, 1.3°'™. 



Florissant. One specimen. No. 8619. 



2. LiTHAGRION UMBRATUM. 

 PI. 13, Figs. 12, 14. 



Two specimens, one a complete wing, the other lacking only the 

 extreme base and an insignificant fraction of the apical margin, represent 

 this species. Both appear to be upper wings. 



The wings are hyaline at base and tip, faintly or distinctly clouded on 

 the disk, the clouded portion having distinct lines of separation from the 

 hyaline area ; the inner line is straight and transverse, crossing the wing 

 from the second postcubital veinlet ; the outer line is bent or curved some- 

 what, subparallel to the apical margin, and runs from the middle of the 

 pterostigma to a little beyond the apex of the short sector, bending on the 

 nodal sector. The wings are petiolated very nearly up to the first postcostal 

 nervule, which is placed shortly before the base of the quadrilateral. Ultra- 

 nodal sector originating from a cross vein a little distance beyond the nodal 

 and shortly before a point midway between the nodus and pterostigma ; 

 its course is more or less zigzag at its origin and again in the middle, but is 

 mostly simple ; inferior sector of the triangle straight in its basal half. 



