364 MEMOIRS OF THE CARNEGIE MUSEUM. 
The Fibula. 
9 
(Plate LX XI.) 
The fibula is complete, but reduced to a slender and somewhat twisted rod- 
like bone, with the greater portion of its shaft lying close to the side of the tibia. 
The proximal attachment for the tibia is not extensive, and distally the bone 
extends well below the tibia, articulating with the fibular face of the astragalus by 
a broad facet. It does not always touch the caleaneum. 
Tue Hinp Foot. 
The Tarsal Elements. 
(Plate LX XII.) 
A great many specimens of the bones of the hind feet were found scattered 
through the different quarries. We mainly utilize those of the articulated skeleton 
for purposes of description. 
The tarsus of Moropus is quite low and broad, but is not completely diplarth- 
rous, the cuboid only supporting the caleaneum, and not sharing its proximal 
articulation with the astragalus, as in Macrotherium grande and other Perissodac- 
tyla. ‘The conditions are more like those found in some of the early Tertiary 
forms, like Phenacodus,” or revealed in the Litopterna of the Miocene formations of 
Patagonia.“ The metatarsals are more uniform in size than the metacarpals, 
and also shorter. They are quite heavy with the proximal ends much expanded, 
having cylindrical shafts, showing, as in the manus, at their distal ends rounded 
surfaces for the reception of the phalanges, succeeded on the plantar side by large 
facets for the sesamoids. The phalanges are short and heavy, but more uniform 
in size than those of the manus. 
MEASUREMENTS OF TARSUS. 
No. 1706a No. 1701 No. 1424 
(M. elatus), (M. petersoni), (M. holland), 
mm. mm. mm. 
Greatest vertical diameter including tuber of caleaneum......... 186 140 1308 
Vertical diameter top of astragalus to distal face of ectocuneiform. 128 88 an 
‘Lransverse diameters: va. jock Cee ee eae tae en ocr 110 82 79 
The Astragalus (Fig. 98)—The most characteristic feature of the astragalus is 
its single distal facet, that for the navicular (Fig. 98, 4), while in the true Perisso- 
% Peterson, O. A., American Naturalist, Vol. XLI, 1907, p. 749. 
° Scott, W. B., ‘“Litopterna of the Santa Cruz Beds,” Vol. VII, 1910, p. 7. 
® Approximate measurement. 
