SCOTT : TOXODONTIA OF THE SANTA CRUZ BEDS. 
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at the distal, and the fore and hind limbs are of approximately equal 
length. In Toxodon, probably also in its contemporary genera, whose 
limb-bones have not yet been found, the hind-limbs are very much 
longer than the fore, a disproportion due chiefly to the great elongation 
of the femur, which has lost the third trochanter and in other ways has 
acquired a resemblance to the femur of the Proboscidea. The other limb- 
bones are extremely heavy and relatively short. 
In the Entelonychia the limb-bones, though of the same general type 
as in the other suborders, are much modified in accordance with the very 
curiously specialized feet. The humerus has remarkably prominent del- 
toid and supinator crests and epicondyles and in one genus ( Diorothe - 
riuni) there is an epicondylar foramen. The fore-arm is much elongated 
and the ulna is, for most of its length, heavier than the radius, which 
probably had considerable freedom of rotation. The femur is also long, 
and antero-posteriorly flattened and has a reduced third trochanter. The 
bones of the lower leg are relatively short, so that the fore-limb is longer 
than the hind, somewhat as in the European Macrotheriwn. The tibia 
and fibula are separate and the former has a distal end of peculiar shape, 
being broad transversely and much compressed antero-posteriorly. The 
fibula is very stout, especially the distal end, which forms a massive 
external malleolus. 
The Feet differ more among the three suborders than does any other 
part of the skeleton, though the unity of plan is made evident by the uni- 
formity of the carpus and tarsus. Throughout the order, at least in all 
the genera of which the feet are known, the carpus is arranged in alter- 
nating series and there is no free central, that element being probably 
ankylosed with the scaphoid. Otherwise, there is no coossification 
among the carpals and the trapezium is always present, except probably 
in the Pampean toxodonts. In the tarsus the astragalus is grooved in 
varying degree, but never deeply, and always has a rounded, convex 
head, which rests only on the navicular and is widely removed from the 
short cuboid. In the known toxodonts the meso- and entocuneiforms are 
coossified, but in the other suborders all of the tarsals are free and none 
is lost. Except in a few of the Typotheria, the calcaneum has a large and 
prominent facet for articulation with the fibula. 
While the fundamental character of carpus and tarsus is thus uniform, 
there are many varieties in details; thus, in the Toxodonta the astragalus 
