EDENTATA OF THE SANTA CRUZ BEDS. 35 



distally, with nearly straight tibial, and deeply concave fibular border ; the 

 trochlea is very oblique and almost entirely distal, but the carina is promi- 

 nent, nevertheless. 



Metatarsal V is much reduced, and is a little longer, though rather more 

 slender, than metatarsal I ; the head bears a very small proximal facet for 

 the cuboid and a much larger lateral one for metatarsal IV, while on the 

 fibular side is a prominent tubercle for the lateral ligament ; the shaft is 

 short, broad and depressed and the trochlea is curiously modified, being 

 oblique and saddle-shaped, while the carina is reduced to a mere tubercle. 



Phalanges are preserved only in connection with digits I, II and III. 

 Of digit I the proximal phalanx is relatively long and narrow, especially 

 at the distal end, and much depressed. In digit II this phalanx is short, 

 depressed and very broad ; the proximal end is deeply notched on the 

 plantar side for the metatarsal carina, while the distal trochlea has a short 

 dorso-plantar diameter and a deep median notch, which is especially 

 conspicuous on the dorsal side. In digit III this phalanx is a little longer 

 and broader, but otherwise similar. 



The second phalanx of digit II is longer, narrower and thicker than 

 the proximal one, and narrows more distally ; the proximal trochlea is 

 divided into two entirely distinct facets and the dorsal border forms a 

 thick, blunt median beak, which fits into the distal notch of the proximal 

 phalanx. In digit III the second phalanx is of similar shape, but some- 

 what larger. 



No other known Santa Cruz genus has ungual phalanges at all resem- 

 bling those of Stegotherium. In digit II the ungual is shaped much as in 

 Tatu, but is somewhat larger and heavier, more convex on the dorsal side 

 and more decurved. In digit III this phalanx is remarkably large and 

 stout, far larger proportionately than in Tatu ; it is broad and thick at the 

 proximal end, tapering to a very sharp and strongly decurved point at the 

 distal end ; the lateral edges are very sharp, the dorsal side strongly 

 convex and the plantar concave, and the subungual process is a prom- 

 inent rugose, triangular area, perforated by two foramina. 



Restoration (Plate II). As a whole, the aspect of the skeleton imme- 

 diately recalls that of Tatu, although with the increased stature are asso- 

 ciated a greater thickness and massiveness of the bones. The most 

 striking difference between the two genera is in the skull, which appears 

 to be much more elongate in the fossil, but is not, when compared with 



