132 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



teriorly and arched inward and forward ; at the distal end, these propor- 

 tions are reversed ; the cnemial crest is very prominent and is continued 

 down the whole length of the shaft, ending on the internal malleolus ; 

 two interosseous crests are present, one posterior, which is prominent 

 near the proximal end, dying away below the middle of the shaft, the 

 other anterior and, for most of its length, a mere linea aspera, but becom- 

 ing prominent distally and uniting with a corresponding crest of the fibula. 

 The astragalar surface has the external condyle larger and deeper than 

 the internal ; the intercondylar ridge is broad and low, but gives off an 

 elongate, tongue-like process from the hinder border, separated by a deep 

 sulcus from the much-reduced internal malleolus. 



The fibula is likewise much compressed and plate-like, but very thick 

 antero-posteriorly, especially near the proximal end ; the distal end is 

 massive, though not very broad, and terminates in a heavy, projecting 

 malleolus, which articulates with the astragalus but not with the calcaneum. 



The pes (Plate XXVI, fig. 8) is short and very heavy, though far from 

 being so massive as in the Pampean genera, among which it most resembles 

 that of Glyptodon. The astragalus has a short and very broad trochlea, 

 which is but moderately grooved and is made asymmetrical by the larger 

 size of the external condyle ; the neck is very wide, but much narrower 

 than the trochlea, and ends in a depressed, convex head; the navicular 

 facet is very large and is reflected far up upon the plantar side of the 

 neck ; the external calcaneal facet is large and but slightly concave, while 

 the sustentacular facet is smaller and nearly plane. 



The calcaneum has a much compressed and rather slender tuber, which 

 diminishes in dorso-plantar diameter toward the proximal or free end and 

 has a broadening of the plantar border, especially on the inner side ; the 

 tendinal sulcus at the free end is shallow and confined to the plantar 

 aspect ; the sustentaculum is prominent and very heavy ; the cuboid facet 

 is large and slightly concave, and prominent tubercles arise from its plantar 

 and fibular sides. There is no contact with the fibula. 



The large navicular is distinctly more like that of the armadillos than 

 is the corresponding bone of the Pampean genera, being low on the 

 dorsal side, but rising high proximally on the plantar, and from the 

 latter side arise two very large, hook-like processes ; of the three distal 

 facets for the cuneiforms, the external one is large and the median very 

 small. 



