SCOTT: ENTELONYCHIA OF THE SANTA CRUZ BEDS. 277 
genus, and, owing to the circumstances of the moment, I was unable to 
see his own specimens and compare them with the photographs. 
Assuming, then, that the La Plata femur has been correctly identified, 
it may be described as follows. The head is large, hemispherical and set 
upon a very short neck, which is directed obliquely upward and inward. 
The great trochanter, though massive and rugose, is low, not rising to 
the level of the head and there is scarcely any notch between them. The 
proximal third of the shaft is very broad, narrowing to a point below the 
third trochanter and thence broadening very gradually to the distal end. 
The shaft is much compressed antero-posteriorly and flattened, as in the 
very large ungulates generally, and the internal border describes a 
strongly concave curve, interrupted only by the second trochanter. 
This is a low, elongate ridge, with convex free border, placed very far 
down on the inner side of the shaft, so far indeed as to make it somewhat 
doubtful whether this ridge be actually homologous with the second tro- 
chanter or not. The third trochanter also has a very distal position and 
is elongate, but rather low, and, while very conspicuous, is yet not very 
prominent. The distal end of the femur is very heavy, especially in 
breadth, which exceeds the antero-posterior dimension inclusive of the 
trochlea. The latter is wide, deeply grooved, with prominent borders and 
nearly symmetrical, the internal border projecting but little in advance of 
the external ; proximally, the trochlea ends abruptly in a nearly straight 
line, and distally, the articular surface is separate from that of the inner 
condyle, connected with that of the outer. The condyles, which are sep- 
arated by a very wide intercondylar space, project but slightly behind the 
shaft, and differ considerably from each other in form and size. The 
external condyle is of nearly uniform width, with straight mesial border ; 
while the internal one is more prominent, both posteriorly and laterally, 
and more strongly convex and widens backward, having a very concave 
mesial border. 
The leg-bones, like those of the fore-arm, are entirely separate and free. 
The tibia (PI. XXX, figs. 6, 6a) is relatively short and heavy, much 
shorter than the femur and distantly resembles that of the Gravigrada, 
with which Ameghino has compared it. The proximal end is broad and 
massive, projecting far externally over the head ol the fibula, and bears a 
prominent spine. The shaft is also very heavy near the proximal end, 
where it is trihedral, and has anteriorly a massive, rugose and T-shaped 
