206 MR. ST. G. MIVART ON THE SKELETON OF THE PRIMATES. 
the Chimpanzee than it does Man or the Gorilla. Sometimes, in the Orang, there is a 
marked antero-posteriorly directed groove above this peroneal tubercle (Pl. XLII. 
fig. 2¢), but it is never bounded inferiorly by such a strongly projecting ridge as 
exists in the Gorilla. 
The tubercle for the calcaneo-cuboid ligament is distinct (Pl. XLIII. fig. 7), but 
not prominent as it is generally in Man. 
The articular surface for the cuboid is nearly vertical; but the depression at the lowest 
part of the tibial side is extraordinarily deep, forming a funnel-shaped cavity (Pl. XLII. 
fig. 4c) for the reception of the very long conical and pivot-like prominence on the 
posterior surface of the cuboid’. 
Astragalus. (Plate XLIII. figs. 8-13.) 
This bone, in Simia, has a very different appearance from that of any higher form, 
owing to the great length and strong tibiad inclination of its neck (Pl. XLIII. fig. 8 a). 
The superior articular surface (for the shaft of the tibia) is sometimes rather more 
concave transversely than in Man or Troglodytes, and it extends backward somewhat 
less. The head of the bone (for articulation with the naviculare) is also more compressed 
from above downwards than in them (Pl. XLIIL. fig. 12 3). 
The difference in size between the articular surfaces for the two malleoli is greater 
than in Troglodytes or Man. That for the peroneal malleolus forms rather a slightly 
acute than a right angle, with the upper surface of the astragalus. That for the tibial 
malleolus forms, in the Orang, a very obtuse angle with the same, but yet not so obtuse 
a one as it does in the Gorilla. It encroaches more on the neck of the bone than in the 
higher forms. That part of the tibial face of the astragalus which is posterior to the 
surface for the malleolus, is much smaller than in Man or Troglodytes, but, as in the 
Gorilla, is separated from the latter by a deep groove (Pl. XLIIL. fig. 10 @), behind which 
the surface is very smooth and rounded. On the other hand, that part of the peroneal 
face which is behind the surface for the outer malleolus (Pl. XLIII. fig. 11) is larger 
than in Man or Troglodytes, is more depressed, and has one or more small openings. 
The groove for the flexor tendon is wider than in Man or Troglodytes, and while more 
sharply limited on its peroneal side than in them, is less so on its tibial side (Pl. XLIII. 
figs. 9 & 13 q). 
The posterior articular surface for the calcaneum has, as in the Gorilla, its anterior 
and inner margin more convex (Pl. XLIII. fig. 97), and its posterior and outer one more 
concave than in Man, its crescentic form being very marked. It is separated from the 
' This is doubtless connected with the great mobility, in the Orang, of the joint between the anterior and 
posterior tarsals, which has been noticed by previous observers. Professor Owen speaks of this, Trans. Zool. 
Soc. vol. i. p. 867; and Professor Huxley remarks, ‘The mobility between the distal and proximal divisions 
of the tarsus is exceedingly great, and is the chief cause of the habitual turning inwards of the sole of the foot,” 
* Medical Times,’ 1864, vol. i. p. 565, 
ee 
