292 PATAGONIAN EXPEDITIONS I PALAEONTOLOGY. 



navicular facet. The cuboid is smaller than in H. longiceps and has a 

 smaller surface for the astragalus ; the calcaneal facet is oblique and con- 

 vex; the distal end is divided into a larger facet for the fifth metatarsal, 

 and a smaller one for the fourth (a very unusual arrangement), the two 

 separated by a distinct groove. A large plantar sesamoid is present. 



The most peculiar part of the hind-foot and that which differs most from 

 Hapalops, is the metatarsus, which, as in all other known contemporary 

 Gravigrada, consists of five members. Metatarsal I is much stouter than 

 in H. longiceps ; it is considerably longer on the plantar than on the 

 dorsal side, where it is cut away by the long, sloping facet for the ento- 

 cuneiform ; the shaft is short, broad and thick, and the distal trochlea has 

 an unusually prominent carina, which is greatly extended planto-dorsally. 



Metatarsal II, though short and stout, is somewhat longer and more 

 slender than in H. longiceps ; the proximal end is broader, overlapping I 

 and III more extensively ; the distal end is remarkable for the immense 

 carina, which projects far in front of and behind the shaft. 



Metatarsal III is the heaviest and, except I, the shortest of the series ; 

 the proximal end is somewhat broader than in the last named species and 

 the extremely short shaft is much more constricted below this proximal 

 expansion, broadening again almost immediately to form the distal end ; 

 the carina has an even more exaggerated development than that of II. 



Metatarsal IV is heavier and much shorter than in Hapalops, not 

 greatly exceeding II in length, and diverges less from III toward the fibular 

 side ; the proximal end has a less oblique and much narrower facet for 

 the cuboid ; the shaft is longer and more slender than in any of the pre- 

 ceding metatarsals and the distal carina, though very large, is less prom- 

 inent than in II or III. 



Metatarsal V is considerably damaged, but is obviously shorter and 

 heavier than in Hapalops ; the proximal end has a broader cuboid facet, 

 but, apparently, no such great wing-like process from the fibular side as 

 characterizes Hapalops, Megalonyx and Nothrotherium, while the distal 

 trochlea is much better developed and has a more prominent carina. 



Comparing the pes of the present species with that -of Hapalops, H. 

 longiceps for example, one is immediately struck by the fact that in the 

 former the foot is more isodactyl, there being no such great difference in 

 the length of the various metatarsals as in the latter, and, owing to the 

 arrangement of the tarsal bones, all five of the metatarsals have their 



