CARBONIFEROUS ARTHROPOD FAUNA 1 95 



The three species just described show a marked agreement in 

 the resting position of the hind legs. In each case the femur 

 is twisted in such a manner that the tibia is directed forward and 

 away from the body. This primitive attitude is retained by a 

 few insects of today, such as stone-flies, earwigs, the P^mbiidae, 

 Gryllotalpa, etc., and by the nymphs of many neuropterous insects. 



Carboniferous, Mazon creek. 



Type. Pal. Coll. No. 9244. 



20. Propteticus infernus Scudder. 



Mem. Boston Soc. Nat. Hist., Vol. Ill, pp. 334-6, Plate XXXI, Figs. 3, 4. 



Type. Pal. Coll. No. 6391. 



The following dichotomy will serve to assist in the assign- 

 ment of the genera of this group : 



Internomedian vein ending in the middle of the lower margin, with numer- 

 ous branches arising from its upper side - - - Strephocladus 



Branches of internomedian springing from below ; if from above not end- 

 ing in the hind margin --------- 2 



2. Internomedian with an adventitious vein running across the externo- 



median into the scapular ----- Aethophlebia 



Internomedian of regular formation ----- . ^ 



3. Externomedian unforked, following the course of the internomedian 



Dieconeura 

 Externomedian forked --------- 4 



4. Scapular vein close to the mediastinal, straight, its principal branch 



arising near the middle of the wing and nowhere far removed from 

 the stem .----.--- Miamia 

 Scapular vein bent, separated from both the mediastinal and its prin- 

 cipal branch -------- Propteticus 



Family Hemeristina Scudder. 



Protodictyon gen. novj' 



Body short, very robust. Pro-, meso-, and metathorax quad- 

 rate, broad. Abdomen robust, the last segments provided 

 with a median keel. Wings, large, broad, mediastinal vein 

 ending in the costa beyond the middle; scapular vein strong, 

 parallel with the mediastinal, emitting a distant under-branch 

 near the base of the wing, which dichotomizes several times in 

 an irregular manner. Externomedian vein contiguous with the 

 scapular stem on its basal portion and then suddenly deflected. 



'TT/jwros, "earliest;" SIktvov "net." 



