MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 183 
Whether, however, it descends more or less than in the Gorilla, it always differs from 
Man and agrees with Zroglodytes in that the inner margin of the anterior surface of 
the trochlea (below the ulnar condyle) is vertical, and not inclined ulnad at its lower 
end as in //omo’. 
As in Man and the Chimpanzee, the surface above the capitellum, in front, is less 
concave than in the Gorilla. 
The surface above the trochlea is almost always perforated’. 
The olecranal fossa is bounded on its radial side by a more marked and extended 
ridge than exists in Man and sometimes in the Gorilla (Pl. XXXVI. fig. 2). This 
ridge is the continuation upwards and backwards of that part of the articular surface 
which projects between the radius and the ulna. 
Radius. (Plate XXXVII. figs. 5-8.) 
The radius is very elongated and sometimes slightly exceeds the humerus in length, 
in which respect, as has been already said in describing the last-named bone, the Orang 
differs from Man and Troglodytes. 
Its length as compared with that of the spine, measured as before, is much greater 
than in Troglodytes, being slightly upwards of three-fifths of that of the latter, instead 
of but little more or less than one-half. Of course the Orang differs much more still 
from Man in this respect. 
The radius is always very nearly as much as, if not a little more than, twice the 
length of the scapula—a proportion not attained in the higher forms. 
The shaft of the bone is considerably curved*, with the concavity ulnad; but though 
much more so than in Man, the curvature is somewhat less than that which appears 
generally to exist in the Gorilla. 
The radius of the Orang is so rounded a bone that it can no longer be said to have 
the three surfaces and three margins existing in that of Man. 
The anterior face, however, is pretty well defined and expands distally; the surface 
for the flexor longus pollicis, however, is very slightly marked, much less so than in 
Troglodytes, while it presents nothing like the concavity whence that muscle takes its 
origin in Man. 
The foramen for the nutrient vessels is situated towards the lower end of the upper 
third of the bone, and rather on the radial side of the anterior surface, instead of on its 
ulnar side as in Man and Troglodytes. It is, however, directed proximad, as in the 
higher forms just mentioned (Pl. XX XVII. fig. 5). 
The lower end of the anterior surface is more concave transversely than in Man, 
’ See Trans. Zool. Soc. vol. y. pl. 3. figs. 1, 5, 8. 
* It is imperforate in both humeri of No. 31 and in those of No, 3H 50. 8, 15. 1 in the British Museum. 
* W. Vrolik remarks “Il me parait que cette courbure est un produit de lage” (Recherches d’Anat. Comp. 
sur le Chimpansé, p. 13). 
