348 
ME. ST. G-EORGE MIVART OX THE SKELETON OE THE PRIMATES. 
exceeds that of the part of the os calcis altogether in front of that posterior articular 
surface, slightly in the Chimpanzee, greatly in Man; and in the Gorilla the first is 
more than double that of the second. The two parts are about equal in length in Pero- 
dicticus ; but in all the rest of the order the first falls short of the second, especially 
in Xndris, and immensely so, of course, in Galago and Tarsius. 
The length of that part of the os calcis which is in front of the posterior articular 
surface for the astragalus falls very short of the antero-posterior diameter of that surface 
(less than half) in' the Gorilla. It also falls short of it, though not to such an extent, 
in Man, the Chimpanzee, Simia, and Hylobates. 
Of the other forms it about equals it in the Nycticebinae ; in the rest it exceeds it, 
greatly so in Indris, and immensely so in Galago and Tarsius. 
The outer surface of the os calcis has generally one or two peroneal tubercles, but in 
the Gorilla *, and sometimes in the Chimpanzee, a very deep groove passes antero- 
posteriorly above one of them (Plate XXII. fig. 6). 
The articular surfaces for the astragalus are generally more nearly equal in size in 
other Primates than in Man, and in the Lemuroidea the anterior one is often the larger. 
The posterior one is less convex, and the two are divided by a relatively wider groove in 
the lower Anthropoidea than in Man and the Gorilla. 
The surface for the cuboides is generally much wider than the posterior articular 
surface for the astragalus ; it is not so, however, in the Gorilla and Man, in which 
forms also it is less concave than in the others. It is very concave in the Nyctice- 
binae, Galago, and Tarsius. 
Astragalus . — The head of the astragalus is generally united to the body of the bone 
by a tolerably long neck. This is very short, however, in Man, slightly more so in the 
Chimpanzee ; and the bone has the minimum of length to breadth in the Gorilla f 
(Plate XXXX. fig, 7). In other forms it is more elongated than in Man, and in the 
Orang it is exceedingly long J. 
The upper surface is always more or less convex antero-posteriorly, and concave 
transversely. This convexity is generally more marked than in Man, but decidedly 
less so (than in him) in the Orang, and still less in Ateles and the Gorilla. This 
upper surface is almost always broader behind than in front ; but the difference is very 
small in Man, and still less in Ateles, Simia, Hylobates, Lemur, and Loris. 
When in Man, the astragalus is articulated with the os calcis, and the bones are 
placed in their natural position, with the long axis of the tuberosity of the os calcis 
vertical, then the upper surface is almost quite horizontal, and the lateral surfaces for 
the malleoli are vertical. 
This condition is not so perfectly attained in any other form. In all other Primates, 
* Noticed by Professor Owen (Comp. An at. of Yetebrates, vol. ii. p. 550). 
f Professor Owen remarks tbat it is broader in proportion to its length than in Man (Comp. Anat. of Verte- 
brates, vol. ii. p. 550). 
% De Beainviele speaks of its elongation in Cheirog'aleus Milii as remarkable ( loc . cit. Lemur, i. 12). 
