SCOTT: TOXODONTA OF THE SANTA CRUZ BEDS. 
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femoral trochlea is less unequally divided into outer and inner facets and 
the dividing ridge is even less distinct. 
As in Nesodon , the leg-bones (PI. XXVII, figs. 6, 7) are ankylosed at 
the proximal, but not at the distal end. Except in size, there is hardly 
any tangible difference between these bones and those of Nesodon , at 
least so far as the damaged specimens at my disposal admit of a com- 
parison. The tibia has a somewhat less prominent and less rugose 
cnemial crest, which ends rather more abruptly below. A more important, 
though not at all striking, difference between the two genera is in the 
character of the surface for the astragalus, which in Adinotherium has a 
better defined intercondylar ridge, covers the distal end of the bone 
more completely and is more broadly continuous with the facet on the 
internal malleolus. This latter facet is also larger and extends over the 
entire fibular side of the process. The fibula lacks the interosseous crest, 
which is so conspicuous on the distal half of the bone in Nesodon , and 
the distal end is relatively narrower, especially on the posterior side. 
There is a close resemblance to Nesodon in the character of the hind- 
foot (PI. XXI, figs. 3, 5, 6, 8, 9), though accompanied with more differ- 
ence of detail than is the case in most of the other skeletal structures. 
A full comparison of the two genera in regard to the pes is not, however, 
practicable, as I have seen no quite perfect example of the hind-foot of 
Adinotherium. The astragalus is proportionately longer and narrower 
than in Nesodon and, on the tibial side, is considerably depressed planto- 
dorsally ; the trochlea is somewhat, though not very much, more deeply 
and narrowly grooved ; the external condyle is relatively larger and rises 
higher above the level of the internal one, and the whole trochlea is 
more convexly arched proximo-distally, while the facet for the fibula is 
broader planto-dorsally. The rugose tuberosity on the tibial side of the 
trochlea, near the proximal end, which is so conspicuous in Nesodon , is 
much reduced and hardly perceptible in Adinotherium. In the latter 
genus the neck of the astragalus is considerably longer and more oblique, 
projecting more strongly toward the tibial side. On the plantar side, the 
two calcaneal facets are more widely separated and the pit between them 
is much shallower, and the sustentacular facet, indeed the whole tibial 
side of the bone, projects much more strongly plantarwards. The ex- 
ternal calcaneal facet is of more uniform width and the sustentacular 
facet is much smaller, more oval in shape, and partly or completely sepa- 
