262 PROCEEDINGS OF THE ACADEMY OF [May, 



G. — Ms separating from M1+2 proximad to the 



subnodus, Rs at the subnodus 



Rhinagrion, Mesopodagrion, Megapodagrion, 



Allopodagrion, Podolestes. 



GG. — Ms separating from Mi +2 at the subnodus, R« 



distad to the subnodus Heteragrion. 



FF. — A separating from the hind margin at, or distad to, 

 the level of the arculus (or not developed as a vein 

 distinct from the hind margin in Perilestes). 

 H. — Ms separating from M1+2 proximad to the 

 subnodus. 



J. — Rs beginning proximad to subnodus 



Rhipidolestes. 



JJ. — Rs beginning at the subnodus 



Neurolestes (3 antenodals), Lithagrion, 

 Philogenia, Nesolestes, Podolestes, Synlestes. 



JJJ. — Rs beginning distad to the subnodus 



Neuragrion (3 antenodals on hind wings), 



Philogenia terraha, Allolestes, Dimeragrion, 



Heteropodagrion, Protolestes. 



HH. — Ms separating from M1+2 at the subnodus 



Chlorolestes, Heteragrion. 



HHH. — Ms separating from M1+2 distad to the 



subnodus Mesagrion, Perilestes. 



The preceding Synopsis, pp. 256-261, will enable one using this 

 Alternative Grouping to distinguish from each other the genera 

 listed under each final rubric. 



A comparison of Synopsis and Alternative Grouping will show 

 that, in spite of a number of differences in the order in which the 

 genera appear in the two schemes, both begin with and both end 

 with nearly the same forms, which may therefore be regarded as, 

 respectively, the oldest and the youngest members, phylogenetically, 

 of the legion Podagrion. 



The Relationships of Phenacolestes. 



// the conclusions reached on pp. 255-256 he correct, 

 Dysagrion of the Eocene of Wyoming, the oldest member of the 

 legion Podagrion now known, cannot have been an ancestor of any 

 of the three known Miocene genera from Colorado, Phenacolestes, 

 Lithagrion, and Melanagrion, because it lacked supplementary sectors 

 between Mi and Cui. Melanagrion indeed possesses one more 

 primitive feature than is found in any of the other three of these 

 extinct genera, viz., Rs begins proximad to the subnodus. 



Phenacolestes has preserved more primitive characters than has 



