Fdrr.] 



166 



[May 15, 



Fig. 5. 



with its inferior border slightly convex. The upper border is broken 

 away. The tuberosity is much thicker and more mas- 

 sive than in the smaller species, where all the bones 

 are gracefully shaped. The sustentaculum is very 

 strongly developed and bears a large facet for the as- 

 tragalus, which facet is elongately oval in shape. The 

 crest formed by the superior or ectal astragalar facet 

 is broken off so that its character cannot be deter- 

 mined. There is a slight prolongation of this facet an- 

 tero-externally which is somewhat more emphasized 

 than in the smaller species. The inferior facet is 

 near the distal end, and is the smallest of all the 

 facets of calcaneum, and does not extend far back 

 from the distal end — elongate in shape. The facet for 

 the cuboid is large, occupying all the distal end of the 

 bone which is more obliquely truncated than usual. 

 The shape is triangular with the apex towards the 

 sustentaculum. 



The astragalus is merely an enlarged copy of that 

 of M. hairdi with some differences of detail. It is pro- 

 portionately broader. The trochlea is more widely 

 open and the condyles are higher and thicker. The 

 neck is of about the same relative proportions as in 

 M. bairdi. The internal condyle as usual is the 

 longer of the two and anteriorly slightly overhangs 

 the navicular facet while in the .smaller species it does 

 not quite reach it. The outer cond3'le is very much 

 shorter than the inner and is separated from the navi- 

 cular facet by quite an interval. 



The navicular is a flat bone, is wide transversely 

 and seems proportionately higher than in M. bairdi. 

 articular surface is stronglj^ concave antero-poste- 

 riorly for the corresponding surface of astragalus. Posteriorly there 

 are two elevations on the inner and outer borders respectively, be- 

 tween which is a wide and shallow depression for the projection on 

 the inferior margin of distal surface of the astragalus. The exter- 

 nal margin of this latter projects strongly downward, extending 

 around the outer edge of navicular. These two characters make 

 a very close interlocking joint so that there is scarcely any direct lateral 

 movement possible. This interlocking is not quite so complete, how- 

 ever, as in M. bairdi, as in this latter the external margin of inferior sur- 

 face of astragalus extends tarlher down on outside border of navicular. 

 This outside projecting border is in the form of a crest which is placed 

 obliquelj' on bone and limits the direction of the movement of the two 

 bones taking part in this articulation on each other to an oblique motion. 

 The distal surface of bone presents a large triangular facet for ecto-cunei- 



Left Foot of 

 M. CoPEi, %. 



The proximal 



