194 PATAGONIAN EXPEDITIONS! PALAEONTOLOGY. 



The trapezoid is shorter than the trapezium, but otherwise quite large, 

 and on the dorsal side is broad, contracting to a blunt edge on the pal- 

 mar ; the proximal end articulates with the scaphoid by a saddle-shaped 

 facet, while the distal end is modelled to fit the curiously complex end 

 of metacarpal II. 



The magnum 'is rather small and narrow and but slightly longer than 

 the trapezoid ; proximally it is covered by the lunar, but the thin and 

 elevated radial border is wedged in between the lunar and the scaphoid ; 

 distally the magnum articulates only with metacarpal III. 



The unciform is large ; on the dorsal side it is both broad and long, 

 but on the palmar side contracts to a blunt point, though without forming a 

 distinct palmar hook ; the contact with the lunar, if present, must be very 

 small and entirely lateral ; the distal end articulates with metacarpal III, 

 which notches it in a curious way, and with metacarpals IV and V, the facet 

 for the latter rising on the ulnar side almost to the proximal end. 



The metacarpus consists of five members, which are straight and have 

 no such appearance of torsion as those of the Pleistocene Gravigrada and 

 the recent ant-bear, the manus having the appearance of a plantigrade 

 unguiculate. 



Metacarpal I has been lost from this specimen, but in other species of 

 Hapalops it has much the shape and relative size of that of Nothro- 

 therium. 



Metacarpal II is proportionately shorter and heavier than in the latter, 

 longer and more slender than in Megalonyx ; the proximal end, which 

 is slightly wider than the shaft, has a large facet on each side for the ad- 

 joining metacarpals, but is connected only with the trapezoid, the facet 

 for which is very complex, forming a deep groove on the radial and a plane 

 surface on the ulnar side ; the shaft is short, stout, slightly curved and of 

 irregularly quadrate section, broadening and thickening slightly to the 

 distal end ; the carina is exceedingly prominent and the rest of the trochlea 

 consists of a narrow surface on each side of it. 



Metacarpal III has much the same shape as in Megalonyx, while in 

 Nothrotherium it is longer and much more slender ; the proximal end is 

 very broad and has five different facets, for metacarpal II, the magnum, 

 two for the unciform and one for metacarpal IV ; the magnum surface is 

 a narrow groove ; the shaft is short and stout, much broader than any of 

 the other metacarpals, and in its proportions is intermediate between meta- 



