202 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. 



The entocuneiform has been lost from the specimen. 



The mesocuneiform is broad and extremely short proximo-distally, 

 and is much less extended in the dorso-plantar dimension than the 

 ectocuneiform. The latter is quite large, especially on the dorsal side, 

 tapering to a blunt point on the plantar ; the distal end is wedge-shaped 

 and fits into the deep groove on the head of metatarsal III. 



The cuboid is rather small, relatively narrower and more pyramidal 

 than in Megalonyx, and is so placed in the tarsus that its long axis is 

 oblique to that of the calcaneum and astragalus, and it lies partially upon 

 the plantar side of the neck of the astragalus, to which it affords consider- 

 able support. The calcaneal facet forms a prominent convexity on the 

 fibular side and that for the astragalus is large, slightly concave and 

 dorsal in position, the two surfaces meeting at the proximal end, to 

 which they give a wedge-like shape. Distally, the facet for metatarsal 

 IV is very large and that for V is very narrow, much narrower than in 

 Megalonyx. 



A large plantar sesamoid is preserved in connection with this pes ; it is 

 flattened and scale-like, but quite thick and heavy and of an irregularly 

 pentagonal shape with rounded angles, and its principal diameter is trans- 

 verse. This sesamoid is placed upon the plantar side of the cuneiforms, 

 extending under metatarsals I and II. 



The five metatarsals are strikingly like those of Megalonyx and 

 Nothrotherium, with somewhat closer resemblance to ' the latter. As 

 in both of the genera named, the three inner members (I-III) are very 

 short and the two outer ones (IV, V) much longer. 



Metatarsal I is short and slender, far more so than in Nothrotherium, 

 in which this bone is very stout ; the facet for the entocuneiform is large 

 and saddle-shaped, the shaft very short and subcylindrical and the distal 

 carina very low. 



Metatarsal II is much larger in all its dimensions than I and is rela- 

 tively shorter and heavier than in Nothrotherium, much more slender than 

 in Megalonyx ; the broad proximal end has a transversely concave surface 

 for the mesocuneiform ; the shaft is very heavy and the distal trochlea is 

 very large with heavy, prominent carina. 



Metatarsal III is much the most massive of the series and, except I, 

 the shortest ; its length slightly exceeds the breadth, while in both of the 

 Pleistocene genera the breadth exceeds the length ; the two sides of the 



