346 



E. II. Sellards — Types of Permian Insects. 



somewhat in front of the middle line of the wing. The two 

 lower branches resulting from this division are simple ; the 

 upper division, after continuing simple a distance of four or 

 five millimeters, breaks into a second set of three veins, of 

 which the two upper are simple ; the lower, continuing simple 

 a variable distance, ultimately breaks into a third set of three 

 veins. The middle vein of these sets of three lies on the fold, 

 is usually weaker, and has the appearance of an interpolated 

 vein. Its attachment is variable, sometimes with the upper 



Fig. 2. The radial sector (Es) and the media (M), as typically developed 

 in the family Protereismephemeridas. The attachment of the middle vein 

 of the sets of three is variable. 



division, sometimes with the lower, or, rarely, directly between 

 the two. In all genera and species thus far made known the 

 radius conforms to this general type. The attachment of the 

 sector is usually with the media. The media is equally con- 

 stant and characteristic. This vein continues simple to or 

 beyond the middle of the wing, where it breaks into a set of 

 three veins, all of which remain simple. The interpolated vein 

 lies in the furrow, the outer branches and the media itself 

 lying on a fold. The attachment of the interpolated vein is 

 variable with the different genera. The media, usually carrying 

 the sector, is fused at the base with the radius. CubituSj and 

 cubitus,, separate just at their basal origin. Each is typically 

 three branches, but in some species additional branches appear 

 at the border. The first anal is a strong, simple, deeply 

 impressed vein, with an abrupt characteristic downward curve 

 at the base. 



A strong brace occurs at the base of the wing. The vein 

 forming the brace is without doubt the costa combined with 

 a strong cross vein. This vein arises at the base of the wing 



