SCOTT: TOXODONTA OF THE SANTA CRUZ BEDS. 1 69 
prominent of the two ; the internal malleolus is long, heavy and bluntly 
pointed and bears on its fibular side a facet for the inner side and neck 
of the astragalus. 
The proximal end of the fibula, which is indistinguishably fused with 
the tibia, is heavy, especially in the antero-posterior direction. The shaft 
is stout, of roughly trihedral shape, and strongly arched outward and 
forward, which gives it a very irregular appearance ; on the distal half of 
the shaft there is a prominent interosseous crest. The distal end is very 
large, both broad and thick, and forms a massive external malleolus, 
which bears two facets, one internal and slightly oblique for the astrag- 
alus, the other for the calcaneum, entirely distal in position, large and 
concave. 
Fig. 31. Fig. 32. 
Toxodon burmeisteri: Left tibia and fibula, Nesodon imbricatus: Left tibia and fibula, 
dorsum, X |. La Plata Museum. dorsum, X i- 
The leg-bones of Toxodon are very similar in type to those of Nesodon , 
but relatively much shorter and far more massive ; they are ankylosed in 
the same peculiar manner, that is, at the proximal end, but not at the distal. 
The tibia has an enormous proximal end and its condyles are very closely 
approximated, but the spine is formed only by the internal one ; the 
cnemial crest also is much more prominent and massive than in the 
