80 



lation. In these depressions open many large vascular canals. A third 

 rough and perforated depression separates the fibular articular surface 

 from the cuboidal one : a more shallow depression marks the outer side 

 of the astragalus behind the fibular surface. The inferior and anterior 

 part, of the astragalus is occupied by one extensive elongated articular 

 surface adapted to the calcaneum, cuboides and naviculare. The navi- 

 cular surface is flat on its upper half, convex on its lower half; the 

 latter part being continued uninterruptedly into the convex cuboidal 

 surface ; the calcaneal surface, which is continued backwards from the 

 cuboidal one, is elongated, being continued to the posterior apex of the 

 bone ; it is rather narrow, and is constricted near its anterior part at its 

 posterior extremity. 



444. The os calcis. 



This bone, which equals in size the os calcis of the Elephant, is chiefly 

 remarkable for the great breadth and length of its rugged posterior por- 

 tion, for its broad, concave, triangular bases, perforated by many large 

 vascular foramina, and for the large and deep tendinous groove, some- 

 times converted into a canal at the outer side of the bone : this canal 

 or groove is nearly an inch in diameter. Above it, at the anterior part of 

 the outside of the bone, there is a wider and shallower canal with a less 

 smooth surface, bounded above by a small tuberosity and in front by a 

 depression and a second tuberosity ; the broad and deep outer surface of 

 the calcaneum behind the foregoing canals is of a rhornboidal figure and 

 is slightly concave, separated from the inferior surface by a broad, rugged, 

 elevated border, and from the superior articular surface by a well-defined 

 margin. The posterior surface of the calcaneum is high but narrow, 

 rising from the tuberous extremity of the heel obliquely upwards with a 

 gentle concave curve to the superior surface, from which it is separated 

 by a small rugged tubercle : this tubercle, and a corresponding one on 

 the extremity of the astragalus above, indicate the points of attachment 

 of a strong posterior ligament. The inner surface of the calcaneum is 

 separated from the posterior surface by a broad and rugged oblique 

 ridge : it gradually deepens to a wide concavity bounded by three large 



