108 Bulletin Wisconsin Natural History Society. [Vol. 8, No. 2. 



Of these Oxyagrion and Amphiagrion are out of question, 

 differing in arrangement of cells and form of stigma. Hyponcura 

 need not be considered because of the large number of postno- 

 dals, stigma, arrangement of cells, and origin of veins, which do 

 not in the least resemble -the fossil. Antiagrion and the Hawaii- 

 an Agrions may be set aside for geographical reasons. Hence 

 only Hesperagrion and Argia need be considered as possible 

 allies. While Hesperagrion offers many points of similarity, it 

 also differs in several important respects, as : 



a) the stigma, narrow in Hesperagrion, more equal-sided in aliena. 



b) the origin of vein M 3 , gradually bent at the origin in Hesper- 

 agrion, abruptly arising in aliena (teste Scudder). 



c) vein M 4 is angulate opposite the origin of M 2 , beyond the nodus 

 in aliena. 



d) the angulation of Cu 2 formed by the first cross-vein on both 

 sides nearest the base i. e., by the cross-vein continuing the distal side 

 of the quadrangle and the postero-marginal cross-vein continuing the 

 distal side of the quadrangle and the postero-marginal cross-vein sit- 

 uated a trifle before it) is very faint and obtuse in Hesperagrion; in 

 aliena both cross-veins are so placed as to form a nearly birectangular 

 angulation, as of a straightened Z. 



e) vein M 1 arises from the junction of the arculus and the upper 

 angle of the quadrangle; in aliena Mj arises from the arculus, dis- 

 inctly separate from the quadrangle. 



The Argia supposition. — For comparison the smaller series of 

 Argia were selected, as typified by A. violacca, this species having 

 the widest known distribution among smaller Argias. Although 

 the type of the genus, A. fnmipennis is not a synthetic type in 

 the present case. Series of clear-winged Argias, as true syn- 

 thetic types, were compared also. 



