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PATAGONIAN EXPEDITIONS : PALEONTOLOGY. 
Metacarpal II is short and stout, with moderately expanded head, which 
overlaps that of me. III. On the radial side is a small, irregular, convex 
facet for the trapezium and the proximal end is occupied by the large, 
transversely concave surface for the trapezoid. The prominence from 
the ulnar side, which overlaps the head of me. Ill, abuts against the 
magnum by a very large facet, and on its distal side is a narrow, con- 
cave, articular band for me. III. The large facet for the magnum is 
extended for nearly the whole dorso-palmar diameter of the bone ; most 
of this surface is deeply concave, but near the palmar side is a small 
convex area, which fits into a corresponding concavity on the side of the 
magnum. The shaft is quite heavy and of irregularly trihedral form, with 
rounded angles, and has large rugose tuberosities upon it, notably on the 
ulnar side below the head (see PI. XXII, fig. 5) and on the palmar face 
somewhat below the middle ; it is moderately curved, with decidedly con- 
cave radial border, and from a point a little below the head increases in 
breadth toward the distal end. The distal trochlea is narrow and not 
very strongly convex, but is extended well upward upon the dorsal face ; 
the carina is low and inconspicuous and is confined to the palmar aspect 
of the bone, being quite invisible in front-view. 
Metacarpal III is the longest and heaviest of the series, though it does 
not much exceed me. II in length. The head, which is but little wider 
than the shaft, though of great dorso-palmar thickness, carries four artic- 
ular surfaces, for me. II and III and the magnum and unciform respec- 
tively. The facet for me. II is very narrow and presents proximally; that 
for the magnum, which is obscurely demarcated from the latter, is very 
large and quite strongly convex palmo-dorsally. The unciform surface, 
which is borne on a massive projection from the ulnar side of the head, 
is large, oblique and of crescentic shape, narrowing toward the palmar 
side. The surface for me. IV is divided into two almost separate facets, 
which are large and concave and placed, one near the dorsal and the 
other near the palmar border ; they are connected proximally by a very 
narrow band of articular surface. The shaft is heavy, antero-posteriorly 
compressed and broadening toward the distal end. Near the proximal 
end, on the anterior face, is a median pit, which probably served for the 
insertion of one of the extensor tendons. Distally, the trochlea is low 
and wide and of compressed semicylindrical form ; the carina is entirely 
palmar and is even less prominent than that of me. II. (PI. XXVI, 
%■ S-) 
