POSTERIOR EXTREMITY. 49 



the elephant. It presents a superior rounded convex articulating surface, 

 which is received into a corresponding excavation of the tibia. Its inferior 

 face is divided into two articulating surfaces, by the anterior part of which 

 it is connected with the naviculare, and by the posterior with the os calcis ; 

 the latter being divided into two surfaces by a deep fossa, which serves for 

 ligamentary attachment. The anterior edge of the astragalus forms a part 

 of the superior face of the foot : it is quite rough, and presents numerous 

 orifices for ligamentary attachment. The posterior edge is compressed and 

 sharp ; being imbedded, as it were, between the tibia and os calcis. The 

 internal edge is rough, and presents a remarkable tuberosity. The external 

 edge is articulated anteriorly with the malleolus of the fibula, and has 

 posteriorly a deep extensive excavation for the accommodation of that bone 

 and its connecting ligaments. 



The astragalus is articulated superiorly with the tibia, inferiorly with 

 the os calcis and naviculare, exteriorly with the fibula. It measures eight 

 inches and a half transversely. 



The os calcis (Plates XIII. and XIV. D) is a very rough, irregular bone, 0s 



Calcis. 



composed of a large posterior rough tuberosity for the attachment of the 

 great tendon, a short thick neck, and an irregular anterior body, articulating 

 with the fibula above, the cuboides below and before, superiorly and inter- 

 nally with the astragalus, anteriorly with the naviculare. This bone is ten 

 inches in length. 



The naviculare (Plates XIII. and XIV. E) is a flattened bone, with a Naviculare. 

 rough superior edge and an irregular inferior. It articulates with the 

 astragalus above, below with the three cuneiform bones, and also with 

 the cuboides, behind with the os calcis. The anterior face of this bone 

 measures nine inches. 



7 



