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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 49. 



in this species is very simple. It consists of a long chitinized proxi- 

 mal joint folded on itself, which carries at its distal end two lateral 

 fleshy lobes, which are thin dorso-ventrally. Arising between the 

 distal ends of these and curving ventrad and cephalad, then dorsad, 

 is the curved tip of the penis, which is supported by two chitinous 

 ribs. This tip, as compared with the complexly lobed tip of the 



27 



Figs. 27-28.— Argia emma, male. 27. Dorsal view. 28. Lateral view. 



vivida penis, is simple in construction. The lateral walls of the 

 genital fossa, when viewed from the side, are almost straight, when 

 compared with the abrupt ventrad development of the i)osterior half 

 of the walls in vivida. 



Segment 10 of the abdomen deeply and naiTowly indented on the 

 median dorsal line of the posterior end, and with a high keel on either 

 side of this indentation. (See figs. 39-40.) The superior appendages 



