1913.] NATURAL SCIENCES OF PHILADELPHIA. 227 



The following account is based, therefore, on six wings in seven 

 impressions. 



Throughout this paper the Comstock-Needham nomenclature 

 for the wing-veins has been emploj^ed. In the previous literature 

 on the living members of the legion Podagrion the Selysian terms 

 have been used. The equivalents of the two systems are therefore 

 appended here. 



De Selys: 



The Principal Characters of Phenacolestes (Plate XIV, figs. 1-5). 



1. Nodus at one-third of the wing-length. 



2. More than two antenodals. (Four in at least two (Nos. 2, 3, 4) 



of these specimens, five in No. 5 and in the two cited from 

 Brit. Mus.) 



3. Postnodals 17-19. 



4. Stigma having its proximal edge oblique. 



5. Cells of the wing generally, posterior to Mi, not greatly elongated 



at right angles to long axis of wing. 



6. The veins generally, posterior to Mi, have but a slight caudal 



curvature shortly before they approach the hind margin of 

 the wing. 



7. Between Mi and Mia is only one row of cells throughout to wing- 



margin. (In No. 5, increased to two rows at five cells' distance 

 from the margin.) 



8. Between Mio and M2 is one row of cells, increasing to two and 



then three rows, and so continuing to wing-margin. 



1 Throughout this paper "Rs" has been used as the equivalent of de Selj^s' 

 "*' subnodal sector. " 



