251 E. H. Sellards — Types of Permian Insects. 



In the left hind wing there is a slight depression not shown in 

 the illustration, continuing the snbnodal vein and running 

 toward the oblique vein, indicating possibly the position of the 

 vein or trachea. A comparison of the position of the subnodus 



Figure 6.— Same area from the 

 right hind wing of Tupus permiqnus. 

 Dotted lines indicate restored border 

 of the wing lost from the breaking of 

 the matrix. Enlargement and letter- 

 ing as in figures 4 and 5, 



Figure 7. — Same area from 

 the wing of a modern dragon fly. 

 Enlargement and lettering as in 

 former figures. 



and oblique vein as seen in Tupus with the position of the 

 trachea as seen in many modern nymphs is instructive. From 

 the nymphs it will be seen that the trachea often lies across 

 the media beyond the separation of M, and M 2 , occupying 



approximately the position of 

 8 the subnodus and oblique vein 



of Tupus. In the adult condi- 

 tion of modern dragon-ilies the 

 subnodus, as a rule, meets the 

 media just at the point of sepa- 

 ration of M, and M 2 . It is prob- 

 able that the subnodus has mi- 

 grated in modern adult dragon- 



Figure 8.-Position of trachea flieS to n ? ts P reS . en ? position from 

 of same area of modern nymph an earlier primitive position, 



dragon-fly, genus Didym ops /after sometimes beyond the forking 



Needham Lettering as above. f M sometimes perhaps 



The indistinct trachea preceding i 2 > , , . r r 



the bridge is present, although not basad Ot that point. As a re- 

 lettered, suit of its important function 



as a brace the subnodus is held 

 firmly in place, while the oblique vein, serving no such respon- 

 sible function, is much less constant in position. 



The cubitus. — Ciij continues from the strong basal origin as 

 a simple sinuous vein meeting the inner border slightly beyond 

 the middle line of the wing. It is observed that the various 

 genera of modern dragon-flies differ not a little among them- 



