NEUBOPTBBA ODONATA AGBIONINA. 



oblique in the saint- si-use. Reticulation dense, mostly tetragonal except- 

 ing in the region of the supplementary sectors of \vhirh there are two be- 

 tween each pair of sectors from the ultranodal to the short .- 

 in the interspace ! the subnodal and the median: none excepting 



the upper ones are curved, and there is also a single very brief one bet 

 the short sector and the superior sector of the triangle Postco>tal space 

 simple or nearly so, the inferior sector forming it extending beyond the mid- 

 dle of tin- \vinir but not reaching the border. Wings enlarging considerably 

 towards the middle, strongly petiolate nearly to the base of the quadrilateral; 

 this is several times longer than broad, enlarging slightly away from the 



. the lower side from a fourth to a third longer than the upper. Nodus 

 situated about one-third the distance from the ba>e to the pt stigma. 



This neims is closely allied to I'hilogenia and Podagrion, the subnodal 

 and median sector-, having a similar origin, but it is clearly distinct from 

 either; it differs from the former in the structure of the pti-ro>tigma, which 

 nowhere departs from the co>tal margin, in the straightness of the supple- 

 mentary sectors, the obliquity of the apex of the quadrilateral, the greater 

 distance of the nodus from the l>;i-e of tin- wing and the le>s petiolated '. 

 more broadly expanded form of the wing. In the number and position of 

 the supplementary sectors, ho\\e\er. it closely resembles it. From 1 

 agrion it differs in the earlier departure of the nodal from the principal 

 vein, the larger number of cellule* below the pterostigma. the much iMvater 

 number of supplementary set-tor>. and the more broadly expanded wing: it 



:ibles it rather than Philo^eiiia in the structure of the ptei-o>tii;ina, the 



lation of the wing, and the position of the nodus. It di tiers even more 

 from I'vsairrion, which 1 have placed in the same group, than from either 

 of these two recent genera. Two species have been discovered, both from 

 Florissant. 



Tulile of the iptciet of Lithagnon. 



Wings clear; postcubitaU ft-w 1 L. hyaliiium. 



Wiugs clouded cxcejit at IJUM- and a]n.-\ : pustcubitals numerous . L. umbratum 



1. LlTHAGRION HYALIXUM. 

 PI. 13, Fig. 4. 



A pair of wings, barely overlapping at the postcostal margin and with 

 the tips broken beyond the middle of the pterostigma, but otherwise in 

 admirable preservation, represent this .-pecies: they appear to be upper wings. 



