SCOTT: ENTELONYCIIIA OF THE SANTA CRUZ BEDS. 
27I 
rugose. The sigmoid notch displays the same remarkable peculiarity as 
that of Nesodon, though with some modifications. The coronoid process 
is less prominent and the facet for the posterior part of the humeral 
trochlea is much broader and less convex transversely, not being 
reflected upward so strongly on the outer and inner sides. The anterior 
humeral surface is entirely internal, as in Nesodon , but is much broader 
than in that genus and is so extended as to project inward beyond the 
plane of the shaft in a shelf-like overhang. Thus there is the same 
strange obliquity of the articular surface, when seen from the front, as in 
the Toxodonta, inclining downward and inward. The head of the radius 
is not embraced by the ulna, but the two are merely in contact, as is 
shown by a narrow articular surface on the outer side of the internal pro- 
jection for the humerus, above described. The shaft has quite a different 
shape from that of Nesodon , being less trihedral and more compressed 
laterally ; it contracts distally but little, so that it is stout and heavy 
throughout. The interosseous crest is short, only the proximal portion 
being present and that not very prominent. The styloid process is 
formed by a sudden contraction of the distal end to hardly more than 
half its width, so that the facet for the pyramidal and that on the radius 
for the lunar are widely separated. The pyramidal facet is simply convex 
and forms an obscure angulation with the large surface for the pisiform. 
In Ameghino’s specimen there is a deep, irregular pit on the distal end, 
internal to the styloid process, but this may be merely an abnormality, 
as may indeed be the pit on the distal end of the radius of the same indi- 
vidual, as mentioned in the preceding description. 
The very remarkable and curious manus (PI. XXX, fig. 1) has been 
quite fully described and figured by Ameghino (’94“, 57, ’94^, figs. 3, 4) 
who emphasizes its many likenesses to that of the Ancylopoda. These 
likenesses are, however, less fundamental than the similarities to the 
toxodont manus, though the fore-foot of Homalodontothermm is at once 
the more primitive and the more highly specialized. The carpus is inter- 
locking or “ diplarthrous,” not serial; the bones of the proximal row are 
relatively lower and those of the distal row higher proximo-distally than 
in Nesodon. The scaphoid is not known, but evidently it was broad and 
rested chiefly upon the trapezoid and, in much less degree, upon the 
magnum ; it appears to have had no contact with the trapezium. 
The lunar resembles that of Nesodon , but is much wider transversely 
