94 



THE PALEONTOLOGICAL DATA 



the fact that the oldest of the Dictyoneuridae known are from the Middle 

 Upper Carboniferous, and that at that period winged insects had existed 



Fig. 83. — Hadentomum americannm (After Handlirsch) . 



for a long time. The stem form of the wing-insect series evidently existed 

 either very early in the Lower Upper Carboniferous or, which is more 

 probable, in the Subcarboniferous. 



In the order Hadentomoidea, represented by a single species, Haden- 

 tomum americanum, from the Middle Upper Carboniferous, and conse- 

 quently contemporaneous with the most generalized of the Palaeodictyop- 

 tera, there is what appears to be a division of the subcosta into two branches 

 (Fig. 83). In the fore wing of this insect the subcosta has two tips: one 

 tip ends in the margin of the wing, the other extends to vein Ri. It may 

 be, however, that the latter is merely the last of the series of cross-veins 

 between veins Sc and Ri. 



In the order Mixotermitoidea, which is represented by only two known 

 genera, we find in Mixotermes lugauensis a forked subcosta (Fig. 84) ; and, 

 among the "Palseodictyoptera incertae sedis" of Handlirsch, Xenoneura 



antiquorum, as figured by 

 ' Scudder (Fig. 73), has a 



forked subcosta. Both 

 of these species are from 

 the Middle Upper Car- 

 boniferous and were, 

 therefore, like Hadento- 

 mum, contemporaneous 

 with the most generalized 

 of the known Pala^odicty- 

 optera. 



In the order Megasecoptera we find a distinctly branched subcosta in 

 Diaphanoptera Munieri (Fig. 85). But in the closely allied Corydaloides 

 and Aspidothorax the subcosta is simple. These are all from the Upper 

 Upper Carboniferous. 



-Sc 



Fig. 84. — Mixotermes lugauensis (After Handlirsch). 



