58 MATTHEW ON OEGANISMS 



Tte marginal vein is distinct but not prominent, and runs along the front margin. 



Tlie mediastinal vein for most of its course runs close to the scapular, but curves 

 outward at the extremity ; its length is more than one-third of that of the costal edge. 



The scapular vein and its branches cover a triangular area terminating at the apical 

 end of the v?ing. The main scapular hardly reaches the apical extremity, but terminates 

 near the end of the costal edge. 



The main scapular branch parts from the main vein not far from the origin of the 

 latter, and at one-third from the same point throws off a branch from the lower side, 

 which without branching goes directly to the lower -part of the apical edge. About half- 

 way from the base of the scapular branch another vein is thrown off from the lower side, 

 and forks at a short distance from the apical edge opposite the tip of the wing. The 

 scapular branch itself forks close to the apical edge near its iipper part. 



The area covered by the median veins is elougately rhombic. The externo-median 

 vein throws oflF two branches, of which the first is stronger than the main vein at and 

 some distance from its origin, but fades away and becomes indistinct long before reaching 

 the margin of the wing. 



About one-quarter of its length from source the externo-median vein throws off a 

 second branch, which goes with a sinuosity toward the base of the apical margin, and 

 nearly touches it. At nearly two-thirds from its extremity this branch throws off a faintly 

 marked vein on the lower side. The rest of the exterus-mediau vein is straight. 



The three remaining veins are simple, short and straight, and are directed toward 

 the internal margin of the wing. The subexterno-median originates near the externo- 

 median, and is about two-fifths of the length of the latter. The interno-median is about 

 two-thirds of the length of the subexterno-median. The anal vein is about half of the 

 length of the interno-median, and the anal area is quite small. 



The nerves in this wing are remarkably regular and simple, those in front of the 

 scapular vein and between the scapular and the main scapular branch are obliquely 

 directed forward and outward, but the remainder of the nerves are transverse. The 

 nerves between the two main branches of the externo-median vein show a tendency to 

 throw off branches backward and outward, and there is a faint tendency to a reticulate 

 arrangement on the smooth space near the inferior margin, below the second branch of 

 the externo-median vein. Biit oA^er the greater part of the wing the nerves are directly 

 transverse between the veins. 



The importance of the scapular vein and its proximity to the costal margin appears 

 to indicate that this is an anterior wing ; and the elevation of the scapular vein marks it 

 as a right wing. 



The remarkable simplicity of the venation in this wing distingu.ishes it from aH the 

 other Devonian insect wings, which are sufficiently perfect to exhibit clearly the character 

 of the venation. Of these wings it seems to be most nearly related to Xenoneura anti- 

 quorum, but it is more simple in the plan of its venation. 



Among Carboniferous insects there is one, Hemeristia occidentalis, which in the plan of 

 the venation is similar to this species {G. Wilsoni), but in the carboniferous species the 

 veins are more numerous and more frequently forked. If, however, the plan of venation 

 be considered, our species may be referred to the Hemeristinse rather than to any other 

 Palaeozoic family of insects ; and of the four sections into which Dr. S. H. Scudder 



