30 PATAGONIAN EXPEDITIONS I PALEONTOLOGY. 



plantar direction, with the plantar border raised much higher than the 

 dorsal. The distal end is almost entirely occupied by the very large facet 

 for the ectocuneiform, which surface is also slightly concave planto-dorsally : 

 the facet for the middle cuneiform is extremely small and that for the 

 internal one is entirely lateral, or postero-lateral in position. 



The entocuneiform is a large, flattened, scale-like bone, which is so far 

 displaced to the plantar side as hardly to be visible when the pes is seen 

 from the front, and its connections are entirely lateral, with the navicular, 

 mesocuneiform and second metatarsal respectively. The mesocuneiform 

 is extremely small, with nearly square dorsal face ; it likewise is much dis- 

 placed toward the plantar side and articulates only with mt. II, not touching 

 mt. Ill at all. The ectocuneiform is very large, much the largest bone of 

 the distal row, and nearly equals the navicular in size ; it has, as compared 

 with that of the horses, considerable proximo-distal diameter, and thus 

 helps materially in making up the great length of the tarsus, which is so 

 striking a feature of this pes. Transversely, the proximal border is concave 

 and the distal convex. 



The cuboid is quite small, especially in width, the length on the plantar 

 side being considerable and the thickness planto-dorsally being much the 

 greatest of its diameters, which is due to the large and massive, though 

 not elongate, hook-like process from the plantar side : the proximal surface 

 for the calcaneum is saddle-shaped, concave and very oblique transversly, 

 convex planto-dorsally ; the distal end has a small, plane facet for mt. IV 

 and, internal to this, a small oblique surface for mt. III. 



The metatarsals resemble the metacarpals in size and proportions and 

 in their inadaptive method of reduction. Metatarsal II is very much like 

 mc. II ; the proximal end bears a small facet for the mesocuneiform and 

 on the plantar side another for the entocuneiform ; it does not overlap the 

 head of mt. Ill and apparently has no contact with the ectocuneiform, 

 though I cannot satisfy myself entirely on this point. Metatarsal III bears 

 the whole weight of the limb and is supported only by the ectocuneiform, 

 the limited contact with the cuboid being obliquely lateral, and there is no 

 articulation with the mesocuneiform. As a whole, the bone closely 

 resembles mc. Ill, but is somewhat thicker planto-dorsally, and the process 

 from the plantar side of the proximal end is much longer and more slender. 

 In all of the specimens which I have examined mc. Ill is of nearly the same 

 length as mt. III. Ameghino's figures ('94<5, pp. 266-7, ^gs. 8-9) make 



