70 
EOCENE BIRDS. 
at the proximal end a rough longitudinal surface, which looks as though 
adapted for squamosal union with a splint bone. The distal condyles are 
of large size, and the usual foramen is present just above the union of the 
external with the median condyle. 
The affinities of this genus are' not sufficiently indicated by the bone 
in our possession, although it is diagnostic for the principal divisions of 
recent Birds. The proximal end resembles the corresponding part in 
the Ostriches and Binornis; while the distal end, so far as preserved, is 
similar to that of the Gastornis (Hebert) of the corresponding horizon in 
France. It is probable that it will be found that the latter genus is its 
nearest known ally. Gastornis has, however, not yet been definitely 
assigned to its place. Prof. A. Milne-Edwards thinks that it is allied to 
the Natatores; while Lartet and Owen have seen in it characters of the 
Cursores. 
Diatryma gigantea, Cope. 
Plate xxxii, tigs. 23-5. 
Proceedings Academy Philadelphia, 1870, p. 11. 
This species was of large size, the proximal end of the tarsometatarse 
being nearly twice the diameter of that of the Ostrich. Its discovery 
introduced this group of Birds to the known faunae of North America, 
recent and extinct, and demonstrates that this continent has not been desti¬ 
tute of the gigantic forms of Birds now confined to the southern hemi¬ 
sphere faunm. The description is as follows: 
The hypotarsus is moderately prominent, with broad, truncate face, 
and does not inclose the ligamentous groove of its inner side. Its superior 
angle is broken away in the specimen. The two foramina which pierce the 
shaft just below the head are subround; they are well separated from each 
other, both on the posterior and anterior faces, marking nearly equal thirds 
of the transverse diameter of the bone. The cotyloid cavities for the tibio- 
tarsus are bounded by an elevated margin, and are separated mediall}" by a 
single low oblique ridge. The groove of the posterior face is particularly 
vide, and the inner part of the shaft is thinned, while the outer border is 
b.’oadly convex. The proximal part of the inner border (as far as it is 
preserved) is marked with a flat surface, which is roughened wdth ridges, 
