230 PROCEEDINGS OF THE ACADEMY OF [May, 



inferior proximal angle of the stigma and the point where Cu2 meets 

 the hind wing-margin, the following formulae for the present material 

 were obtained: 



No. 1: 1, 1, 2, 1, 2, 2, 3, 2. 



No. 2: (too imperfect). 



No. 3: 1, 1, 2, I, 2, 2, 3, 2. 



No. 4: 1, 1, 2, 1, 2, 2, 3, 2. 



No. 5: 1, 1, 2, 2, 2, 2, 3, 2. 



No. I 15,049: 1, 1, 2, 2, 2, 2, 3, 2. 



We have here two different formulae, neither of which agree with 

 either of Prof. Cockerell's formulae. 



Guided b}^ the amount of variation in venational details of one 

 and the same living species of Agrioninae, I am of the opinion that 

 the differences shown by the present material, inter se and from 

 Prof. Cockerell's data, do not justify the specific separation of the 

 specimens before me from Ph. mirandus. 



All of the present material show more or less distinctly the dark 

 band across the wing, described by Prof. Cockerell; it is best illus- 

 trated in our figure 5. 



Phenacolestes agrees with the venational characters of the legion 

 Podagrion, as stated by de Selys in 1886,^ with the one exception 

 that the wings are not "petiolees beaucoup plus loin que la nervule 

 basale postcostale." I think that there can be no doubt that its 

 nearest living aUies are to be found in this group. I have therefore 

 made comparisons with a number of genera of this legion, especially 

 American, with the results set forth below. As I have had only 

 five of the fossil wings and photographs of one other before me and 

 am unable to determine whether all of them are of the fore or hind 

 pairs, I have not thought it necessary to employ any great number 

 of specimens of the living species for these comparisons. 



Comparison of th£; fossil Dysagrion (packardii, fredericii) 

 WITH Phenacolestes. 



According to the figures and descriptions of this Eocene genus, 

 from the Green River shales of Wyoming, given by Scudder,^ Dysa- 

 grion and Phenacolestes agree in the characters above numbered 

 2, 3, 4, 5, 7,'^ 10, 11,^ 14, 156, 16a and b, 20, 21a and b, and 22, and 



5 Mem. Couron. Acad. Belg., XXXVIII, p. 30. 



6 Tertiary Insects of North America, 1890, pi. 6, figs. 3, 9, 14 and pp. 128-133. 

 ' In D. packardii, but not in D. fredericii. 



8 As Scudder has pointed out, p. 129, however, the subnodus is bent proximad 

 (instead of distad as is the case in Phenacolestes). 



