72 T. D. A. Cocker ell — Descriptions of Tertiary Insects. 



Subquadrangle without a cross-nervure ; subnodus 

 oblique. . . . 1. 



1. Nervures and stigma pale ferruginous ; ten postnodal sec- 



tors ; stigma very oblique, with the inner side as long as 

 the outer. Hesperagrion prcevolans Ckll. 



Nervures dark brown or black ; stigma ordinary. . . 2. 



2. Costa before nodus conspicuously arched ; 11 postnodal 



cross-veins ; curved basal section of M 3 very short. 



Agrion exsularis Scudd. 

 Costa before nodus hardly arched ; curved basal section of 

 M 3 longer. 3. 



3. Postnodal cross-veins 10 to 11 ; upper side of quadrangle 



longer than inner. Agrion mascescens Scudd. 



Postnoclals 14 ; upper side of quadrangle a little shorter than 

 inner. Enallagma florissantella Ckll. (probably 



upper wing). 



The postnodals in living Enallagma are from 9 to 11, at 

 least in the species examined. I find the upper side of quad- 

 rangle much longer than inner in E.fischeri and E. exsulans ; 

 but in an upper wing of E. carunculatnm the inner is longer 

 than the upper. The difference between the quadrangles of 

 A. mascescens and E. florissantella cannot be due to their rep- 

 resenting different wings, for the upper wing of mascescens is 

 known, and has the upper side of the quadrangle very long. 



The position of the base of the quadrangle seems to be 

 of some significance : 



(1) Base of quadrangle conspicuously before levei of midmost 



point between antenodal cross-veins. A. mascescens. 



(2) Base of quadrangle at or near level of midmost point. 



E. florissantella, A. exsularis, E.fischeri -y 

 E. signatum, E. hageni. 



(3) Base of quadrangle far beyond level of midmost point, not 



far from level of first cross-vein. 



E. carunculatum, E. civile. 



Trichocnemis aliena Scudder. Figure 3. 



A wing was obtained at Station 13 B ( W. P. Cockerell ). 

 The most striking character, the crossed subquadrangle, is 

 unfortunately not visible in our specimen, but there is no reason 

 to doubt that it exists, as represented in Scudder's figure. Mr. 

 Williamson writes : 



"Earaphlebia is the only Agrionine genus known to me with 

 crossed subquadrangle. It is a character that disappears with 

 reduction in the Calopterygirue ; e. g., Diphlebia has it rarely 

 crossed. Cyanocharis has quadrangle but not subquadrangle 

 crossed ; Devadatta has both quadrangle and subquadrangle 



