THE OSTEOLOGY OF ELOTHERIUM. 307 
The metacarpus consists of four members, two functional, the third and fourth, and 
two mere rudimentary nodules, the second and fifth. 
Metacarpal IT is not preserved in any of the specimens which I have seen, though it 
is figured by Marsh (93, Pl. VIII, Fig. 4), but the facets on the neighboring bones show 
that it was carried by the trapezoid and retained a lateral connection with the magnum, 
excluding me. i from any contact with the trapezoid. The manus of Elotheriwm is thus 
-a typical example of what Kowaleysky has called the “inadaptive mode” of digital 
reduction. 
Metacarpal IT is long and massive. The head is heavy, enlarged in both dimensions, 
and has a stout prominence upon the palmar side; it bears a broad, saddle-shaped surface 
for the magnum. On the radial side is a depression for me. ii, at the proximal end of 
which are two small facets for that bone. The unciform process is very large, prominent 
and heavy, and projects far over the head of me. iy, but is, as usual, confined to the 
dorsal half of the head. On the distal side of this process and on the ulnar side of the 
shaft is a continuous, concave facet for the head of me. iv. A second facet for the same 
metacarpal is borne upon the palmar projection from the head. The shaft of mc. ii is 
broad, but much compressed and flattened antero-posteriorly ; both width and thickness 
are nearly uniform throughout, but increase slightly toward the distal end. The distal 
trochlea is broad and rather low, but is reflected well up upon the palmar face; on the 
dorsal side it is demarcated from the shaft only by an obscure ridge, with no deep 
depression aboye it. The carina is yery prominent, but is confined entirely to the palmar 
face. The lateral pit on the ulnar side is large and deep, but that on the radial side is 
faintly marked. 7 
In Kowalevsky’s specimen (’76, Taf. XX VI, Fig. 21) the third metacarpal does not 
differ in any important way from that of the American species, though the magnum 
facet is somewhat more concave transversely and the shaft is rather more slender. In 
Anthracotherium (Kowalevsky, ’73, Taf. XIII, Fig. 80) me. iii is very similar to that of 
Elotherium, but is relatively heavier; at the proximal end the tubercle for the insertion 
of the extensor carpi radialis muscle is more conspicuous, and the palmar projection of 
the head more prominent. 
Metacarpal IV is a little shorter and narrower than me. iii, with which it articulates 
by two large facets, separated by a wide and deep groove ; of these facets the dorsal one, 
which is overlapped by the unciform process of me. iii, is strongly convex, while the 
palmar facet is flat and borne upon the palmar projection. The ulnar side has a shallow 
groove, in which lies the nodular me. vy; the articulation with the latter is by means 
of a single, small, triangular facet. The shaft is somewhat narrower transversely than 
that of me. ili, but is otherwise like it, as is also the distal trochlea. 
