AS COMPARED WITH THOSE OF LIVING TYPES. 191 



The v. mediastina and v. scapulctris run nearly parallel to each other throughout their 

 course. The v. scapularis, at about one third the distance from its origin to the apex, 

 sends out a branch, which curves outwards and considerably downwards, again curving 

 upwards, so that when about two thirds the distance from the base it is as far from the 

 main stem as that is from the front margin ; beyond this, it keeps apparently parallel with 

 the main stem; at the deepest part of its curve it sends out a branch about as divergent 

 from it as it was from its parent stem, which continues directly to the margin, and again, 

 but a short distance further on, it sends forth another, which runs parallel to the former. 

 The v. extcrno-media is found a short distance from the base in close contiguity with the 

 v. scapidaris, but forking as it separates from the former, the upper branch continues a short 

 distance in close contiguity to it, and then passes unchanged to the border of the wing 

 parallel to the lowermost branch of the v. scapularis ; the lower branch runs in a direction 

 parallel to the general course of the upper, and forks once a little more than half way to 

 the border. The v. interno-media forks at its origin, both forks running very nearly parallel 

 and in quite close contiguity to one another, and parallel to, but rather distant from, the 

 lower branch of the v. externo-media. The upper fork again forks at a little distance from 

 the origin, the forks keeping in close contiguity. The lower fork sends off from its lower 

 side one or two slightly curving, rather divergent branches. Of the origin and branching 

 of the v. analis little can be said ; the branches are rather numerous and distant, and sub- 

 parallel to the lower fork of the v. interno-media as continued in its first branch, and the area 

 covered by it is large and well developed. All of these veins and branches are connected 

 together by numerous cross-veins, which are quite prominent, equidistant, and equally dis- 

 tributed throughout the wing, much as in most Ephemerina. 



The lower wing differs from the upper, so far as can be determined, in that the branch of 

 the v. scapularis does not curve towards the main stem, and that there are other branches to 

 the v. scapidaris beyond the first, parallel to that. The veins below this were not easily 

 distinguishable. 



Genus Hemeristia Dana. 



Prothorax equally wide throughout ; the sides straight ; the anterior and posterior bor- 

 ders slightly if at all convex ; (fore ?) femora as in Miamia, but proportionally broader, 

 though with the same flat surface on each side of a slightly swollen middle ridge. 



Wings of large size, probably extending considerably beyond the body, the costal border 

 probably quite straight during the first part of its course, curving broadly towards the ex- 

 tremity, probably with the extremities rounded and without a pointed apex, and with a full 

 anal area and angle. The second branchlet of the principal branch of the v. scapularis in 

 the upper wing, previous to the origin of the third, is connected with the principal branch 

 by sinuate cross- veins as frequent as the cross-veins in other parts of the wing. 



Hemeristia occidentalis Dana. 

 The prothorax here is so indistinct and poorly defined as to be incapable of specific de- 

 scription, or of measurements. Mesothorax, .25 in. broad ; the fragment of the (fore?) 

 femur is .10 in. broad. The wings, too, being but partially preserved, it is impossible to 

 give accurate measurements, save of parts within a wing. The probable expanse is 5.15 

 in. ; the distance, when the wings are at rest, between the first branching of the v. scapu- 

 laris on one wing and that on the other upper wing, is .50 in. The estimated breadth of 



MKMOIRS BOST. SOC. MAT. BUT. VOL. I. Pt. 2. 49 



