ARTHROPOD A— INSECTA. 



439 



Order MEGASECOPTERA Brongniart. 



This order, with 22 known species, is represented by two species 

 in the Kittanning horizon and i species in the Lower Permic of 

 Kansas. They are especially distinguished by the tendency toward 

 degeneration shown by the specialization of the anal part of the 

 wing, as well as the reduction in number of the cross-veins, their 

 regular arrangement, and the partial coalescence of the media and 

 cubitus with the base of the radius. There is further a differentia- 

 tion of the thoracic segments by the diminution of the prothorax. 



Fig. 1744. Adiaphtharsia ferrea Handl., Mazon Creek, 111. Carbonic. 



Examples: Adiaphtharsia ferrea Handl. (Fig. 1744), from Mazon 

 Creek, 111. (Alleghany), and Opter brongniarti Sellards, from the 

 Permic of Kansas. 



Order PLECTOPTERA Packard. 



True Ephemera, or May Flies, have, until recently, been known 

 from the Palaeozoic only through examples from the Russian 

 Permic, but the recent discoveries in the Permic of Kansas have 

 added 14 new American species to this group. They are included 

 by Sellards (1907) in his new family Protereismephemeridce. The 

 prothorax and head are of medium size, the thorax as a whole 

 large and arched, the mesothorax and metathorax being of equal 

 size or nearly so ; abdomen long and slender, terminating in stream- 

 ers ; wings elongate, with rounded inner border, the two pairs equal 



