190 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
small and less marked than in Man. The surface which joins the unciforme (Pl. XL. 
fig. 11 a) is strongly concavo-convex, and thus differs much from that in Man, and more 
resembles the corresponding surface in Troglodytes. 
Pisiforme. (Plate XLII. figs. 12-14.) 
The pisiforme of the Orang is much smaller, both absolutely and relatively, than 
that of the Gorilla, and rather so than that of the Chimpanzee. It is always shorter 
than in the last-named form, but yet, sometimes at least, differs from the pisiforme of 
Man in being rather longer than broad. Its palmar surface (Pl. XLII. fig. 13) is slightly 
concave, and the bone projects downwards and ulnad near the unciforme process. 
Trapezium. (Plate XLII. figs. 15-20.) 
A striking difference exists between this bone in the Orang and the homologous one 
of the Gorilla, inasmuch as the two large tuberous processes which exist in the latter 
form! are here wanting. It differs in the same way, though to a less degree, from the 
Chimpanzee’s; and even as compared with Man’s, the tubercle and groove of its palmar 
aspect are somewhat less marked (Pl. XLII. fig. 17). 
The saddle-shaped surface for the metacarpal of the pollex is always (as also in 
Troglodytes) much inferior in relative size to that of Man; indeed, even in absolute 
size, it is much inferior to his. There seems, however, to be considerable variation as 
to the development of this part, as sometimes (Pl. XLII. figs. 15 & 17, a) there is a very 
distinct, though small, saddle (the surface being strongly concavo-convex), while in 
other instances (Pl. XLII. figs. 16 & 18, a) both concavity and convexity are very slight. 
This variation is not confined to the Orang, but exists also in T’roglodytes’. 
The surface for articulation with the metacarpal of the index (Pl. XLII. fig. 174) is 
generally very close to that for the metacarpal of the pollex—a circumstance in which 
the Orang differs from Troglodytes, and resembles Man. ‘The surface for the index 
looks more palmad than in Man or Troglodytes, but, as in them, it is continuous with 
the articular surfaces for the trapezoides and scaphoides. ‘The distal pair of these three 
surfaces form a more marked angle with each other than in Man and Troglodytes ; 
while the proximal pair (for trapezoides and scaphoides) generally meet together at a 
rather more open angle than in those genera. A sesamoid® bone is interposed between 
the trapezium and the scaphoides on the radial side of those bones. 
‘ Owen, Trans. Zool. Soe. vol. v. p. 10. 
2 The saddle is unusually little marked in the skeleton of a Gorilla, No. 5779 A, in the Museum of the Royal 
College of Surgeons; and in the detached and articulated manus of a Chimpanzee, No. 744, in the same collec- 
tion, it is absolutely wanting. Professor Huxley has noticed the absence of a saddle-shaped surface in this 
species. See ‘ Medical Times,’ 1864, vol. i. p. 428. 
3 Figured by Prof. Vrolik in Todd’s Cyclopedia of Anat. and Phys. vol. iv. p. 204, fig. 1247. Mr. W. H. 
Flower also informs me he observed its existence in the wrist of an adult male Orang in the Leyden Museum. 
