scott: toxodonta OF THE SANTA CRUZ beds. 
!77 
The thoracic region of the vertebral column is long and, anteriorly, its 
spines are very high, descending rapidly backward, so as to form a prom- 
inent hump at the withers, while the lumbar region is rather short and 
not very stout. The sacral and caudal vertebrae are not known, but the 
former may be restored from those of Adinoiherium, in which the sacrum 
is long and composed of no less than six vertebrae. The thorax is long, 
deep and very capacious. 
The limbs are short and moderately stout and the anterior pair are 
somewhat shorter than the posterior, though the difference in length is, to 
a great degree, compensated by the very large scapula, which has a highly 
characteristic form, with broad blade and prominent spine, which termi- 
nates in a distinct acromion and bears two very large and conspicuous 
metacromia. The humerus, which is short and heavy, is not especially 
characteristic, but the fore-arm is remarkable for the great size of the ulna, 
which, for most of its length, is heavier than the radius. In contrast with 
this, the tridactyl manus is extremely small in proportion to the size of 
the animal and the unguals of the lateral digits are almost claw-like. 
The pelvis is rather short and heavy, but the iliac plate is only moder- 
ately expanded and everted. The femur is relatively long and stout and 
has a small though very distinct third trochanter, and the patella is very 
thick and massive. Tibia and fibula are ankylosed at the proximal, but 
not at the distal end, and the fibula, though much compressed laterally, is 
still very thick antero-posteriorly. The pes is even smaller and weaker than 
the manus ; the calcaneum has a short and very heavy tuber and articu- 
lates in the normal manner with the cuboid. In one of his latest papers, 
Gaudry figures and describes the pes of Nesodon as thoroughly plantigrade 
and he gives certain reasons, the force of which must be admitted, for 
this conclusion (’o6, 28, fig. 53). A study of all the articulations in- 
volved, however, together with the shape of the ungual phalanges, ren- 
ders the digitigrade attitude more probable, in my judgment. The 
question is a notoriously difficult one in the case of animals which have 
no near analogues in the modern world. In size, N. imbricatus , which is 
the abundant Santa Cruz species, does not greatly exceed the American 
tapirs, though it is decidedly a heavier and stouter animal, with pro- 
portions not unlike those of the early rhinoceroses. 
A comparison of the skeletons of Nesodon and Toxodon (cf. PI. XII, fig. 
2, with Lydekker’s plate, ’93) reveals many differences between the Santa 
