MR. ST. G. MIVAET OX THE SKELETON OF THE PRIMATES. 205 



forms. In absolute length this segment falls short of that of the Chimpanzee, and it is 

 very much shorter than the homologous part in Man and the Gorilla. 



Compared with the length of the spine, that of the tarsus is very slightly less than in 

 the Chimpanzee, but falls more short of that in Man and the Gorilla. The proportion 

 borne by it to the whole length of the pes is more characteristic, as in the Orang it 

 appears to be only as about 26-6 to 100, while in Troglodytes it is 36 or 40 to 100, and 

 in Man is as about 46 to 100. 



Calcaneum. (Plate XLIII. figs. 2-7.) 



The OS calcis of the Orang is very unlike that of Man, or that of the Gorilla, and 

 more resembles that of the Chimpanzee. The projection of the heel backwards 

 beyond the hinder margin of the posterior articular surface for the astragalus, some- 

 times about equals, sometimes falls short of the antero-posterior extent of that surface. 

 The Orang in this differs widely from Man, and still more from the Gorilla, in which 

 last the length of the os calcis behind the posterior margm above-mentioned exceeds 

 that of all the bone anterior to it. In the Chimpanzee the length of the os calcis 

 behind the posterior articular surface for the astragalus does not quite equal the 

 antero-posterior extent of that surface, which, again, exceeds that of the bone in 

 front of it. 



In the Orang the length of the os calcis anterior to the same surface (PI. XLIII. 

 fig. 6) sometimes equals, sometimes falls short of that of the bone behind it. The 

 upper surface of the last-mentioned posterior portion is more or less concave antero- 

 posteriorly (PI. XLIII. figs. 2 & 3), more so than generally in the Gorilla, though 

 not so much so as in the Chimpanzee. 



The posterior surface of the tuberosity is more narrow' transversely than in Man 

 or Troglodytes, and is prolonged both upwards and downwards, the latter making the 

 plantar surface much concave antero-posteriorly (PI. XLIII. figs. 2, 3, & 5). Although, 

 when the surfaces for the astragalus are horizontal, the tuberosity inclines strongly tibiad 

 at its plantar end, — yet this inclination is (sometimes at least) not so great as in the 

 Gorilla". The outer or peroneal face of the calcaneum has a somewhat more human 

 aspect than has that of the Gorilla, inasmuch as it is vertically less convex and more 

 extended, relatively, than in the latter ; sometimes even there is a slight vertical 

 concavity. 



The posterior articular surface for the astragalus is not so convex as in Troglodytes, 

 and it is more posteriorly placed, with respect to the anterior articular surface, than is 

 the case in that genus or in Man. As in the Chimpanzee, there is no trace of a second 

 posterior plantar tubercle ; that for the external lateral ligament is more posterior in 

 position than it is in any of the higher forms, though in this the Orang more resembles 



' Professor Huxley remarks, " The calcaneal process is narrow from side to side," ' Jlcdical Times," 1S64, 

 vol. i. p. 56.5. '" Dr. Lucae remarks this, loe. cil. p. 31.14. 



