'344 PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



tended down the shaft and projects very little. The shaft is broad, antero- 

 posteriorly compressed, and contracts from the proximal end, expanding 

 again at the distal end. The astragalar surface is quite different from that 

 of Hapalops, being much more distinctly divided into two facets by an 

 intercondylar ridge and by a short, deep sulcus from the dorsal border ; 

 the inner facet is much more concave, the outer one very shallow ; the 

 internal malleolus is much less reduced, the deeply grooved process which 

 arises from the inner side, behind the malleolus, is decidedly less prominent. 



The fibula, which has lost the proximal end, has a stout, trihedral shaft, 

 somewhat compressed laterally, and with a rugged linea aspera along the 

 postero-internal border. The distal end forms a very massive external 

 malleolus, which is not unlike that of Megatherium, but extends much 

 farther below the level of the tibia. 



Little is known of the pes. The astragalus (Plate LX, fig. 2) differs in a 

 marked way from that of all the contemporary Megalonychidcz, and especi- 

 ally in relative shortness and width, in the deeper grooving of the trochlea, 

 and in the incipient transformation of the inner condyle into the odontoid 

 shape seen in Megatherium. 



The calcaneum has a broad, depressed, plate-like tuber, not unlike that 

 of the Megalonychidce, but the sustentaculum is much more prominent 

 and its astragalar facet presents dorsally, at right angles to the cuboid 

 facet, instead of being almost parallel with it. The facet for the cuboid is 

 remarkably narrow planto-dorsally, and below it is a thickened, callus- 

 like mass of bone. 



The ungual phalanges of the pes are less different from those of Hap- 

 alops than are the unguals of the manus ; being shorter, more curved and 

 compressed and more sharply pointed than the latter. 



MEASUREMENTS. 



Femur, length from head 298 Tibia, distal thickness 040 



" " " great trochanter .. .310 Fibula, estimated length 218 



" proximal width 131 " width of shaft 017 



" distal width 104 " thickness of shaft 02 1 



Tibia, length 230 " distal width 042 



" proximal width 104 " thickness 049 



" " thickness 071 Ilium, length 162 



" distal width 079 " greatest width 205 



