1913.] ■ NATURAL SCIENCES OF PHILADELPHIA. 225 



the fossil odonate phenacolestes, with a discussion of the 

 venation of the legion podagrion selys. 



by philip p. calvert. 

 Contents. 



Phenacolestes Material Studied, p. 225. 



The Principal Characters of Phenacolestes, p. 227. 



Comparisons of the fossils Dysagrion (p. 230), Melanagrion (p. 231) and Lithagrion 

 (p. 232) with Phenacolestes. 



Comparison of Thaumatoneura with Phenacolestes, p. 233. 



Relationships of Thaumatoneura, p. 233. 



Comparisons of Philogenia (p. 23.5), Megapodagrion [Allopodagrion] (p. 236), 

 Paraphlebia (p. 237), Dimeragrion (p. 238), Heteragrion (p. 239), Mesagrion, 

 Heteropodagrion and Neuragrion (p. 240), Rhipidolestes (p. 241), Podopteryx 

 (p. 242), Argiolestes (p. 243), Chlorolestes (p. 244) and Various Old World 

 Genera (p. 244) with Phenacolestes. 



General Discussion of the Value of the Venational Characters compared in the 

 preceding Genera for the Determination of Relationships, p. 245. 



Synopsis of Venational Characters of Genera of the Legion Podagrion, p. 256. 



Outline of an Alternative Groui)ing of the Genera of the Legion Podagrion, p. 261. 



The Relationships of Phenacolestes, p. 262. 



On the Subfamily Dysagi'ionina? Cockerell, p. 264. 



Additional Data on Dimeragrion, n. gen., p. 265. 



Bibliography, p. 270. 



Explanation of Plate XIV, p. 272. 



Phenacolestes Material Studied. 



In 1908, Profe.ssor T. D. A. Cockerell described (1908a) two species 

 of fossil Odonata from Station 14, Florissant, Colo., as Phena- 

 colestes mirandus and P/!.(?) parallelus. A little later (19086) he 

 added a note based on an additional fragment which he referred to 

 the latter species, and in another place (1908c) he gave a figure 

 showing the body as well as the wings, the previous accounts having 

 referred to the wings only. In connection with the original descrip- 

 tion he quotes from a letter from Professor Needham who almost 

 implies that Ph. mirandus is to be placed in de Selys' legion Podagrion 

 of the Agrioninffi (1908a, p. 63). 



In the latter part of 1910, Professor Cockerell wrote to me that 

 he had found more wings of Phenacolestes, and requested me to study 

 them, in view of some differences of opinion as to its relationship to 

 modern dragonflies. 



When I accepted this offer, Professor Cockerell sent me four 



