212 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
of Man. The external proximal process, or tuberosity (Pl. XLIII. figs. 52 & 53 a) 
is smaller in the Orang than in the higher forms; and in this the fifth metatarsal 
differs less from the fifth metacarpal than in them. 
As in the Gorilla, the tibial articular surface is less antero-posteriorly extended than 
in Man. 
The proximal surface of this metatarsal is very much more concaye and less convex 
than is the corresponding surface of the fifth metacarpal. 
Digits. 
The proximal phalanges of the four outer digits are very much curved", with the con- 
cavity downwards (Pl. XLI. fig. 12), much more so than are their homotypes of the 
manus. ‘They are also narrower transversely, less flattened below and rather shorter, 
than are the latter. In these last three points, however, they differ less from their 
homotypes than do the same proximal phalanges of Troglodytes from their serial homo- 
logues, and of course very much less than do those of Man. The proximal phalanx of 
the hallux is much shorter than is the homotypal segment in the Orang’, a circumstance 
in which it differs from all the higher forms. ‘The second phalanges of the four outer 
digits are shorter and narrower than are their homotypes; but again the difference is 
less than in 7roglodytes, and greatly less than in Man. 
The second phalanx of the hallux is often absent®, but when present is much shorter 
than is its homotype of the pollex*, in which respect the Orang again differs from the 
superior forms. ‘The third or distal phalanges scarcely differ in length from those of 
the manus, and at the most they are but a trifle shorter, thus agreeing with Troglodytes 
and differing much from Man. 
The hallux with its metatarsal, when compared in length with the spine, I have found 
to be only as about 13°6 to 100, instead of from about 17 or 18 to 100 as in Man and 
Troglodytes ; compared with the length of the entire pes, it barely exceeds a quarter, 
instead of approaching one-half as in them. ‘The index with its metatarsal, as compared 
with the length of the spine, is very much longer than in the higher forms, as also is the 
third digit. Without their metatarsals, these digits, when compared with the length of 
the entire pes, are not so very much longer than in the Chimpanzee (39 and 42 to 100, 
instead of 32 and 34), but they of course greatly exceed those of Man. 
The proportion borne by the whole hallux to the whole pollex is strikingly different 
" Professor Huxley, ‘ Medical Times,’ 1864, yol. i. p. 565. 
? See Lucae, loc. cit. plate iii. figs. 5 & 9. * See Lucae. /oc, cit. plate iii. tigs. 5 & 9, 
* Camper found this to be the case in seven out of eight Orangs (Cluvres, tom. i. p. 54). Two phalanges, 
however, are recorded in two cases by Professor Owen, Trans. Zool. Soe. vol. i. p. 867. W. Vrolik, Joc. cit. 
pp. 15 & 16, says, “ One or two phalanges are present,” and appears inclined to think that the distal one may 
disappear with age. De Blainville, loc. cit. p. 32, records five cases, in cach of which the hallux had two 
phalanges, 
