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PATAGONIAN EXPEDITIONS: _ PALAEONTOLOGY. 
a large tubercle for tendinal attachment. The shaft is long and slender, 
broadening but slightly to the distal end, and subcylindrical in shape, 
with nearly equal transverse and dorso-palmar diameters. The distal 
trochlea is most peculiar ; instead of projecting forward from the dorsal 
face of the shaft, or being coincident with the latter, it is displaced far 
toward the palmar side, its proximo-distal axis making an angle of nearly 
45 0 with that of the shaft. Dorsally, the articular surface is at first con- 
cave, where it is reflected upon the overhanging distal end of the shaft, 
while the trochlea proper is a low, transverse semicylinder. The carina 
is quite prominent, but so completely palmar in position as to be invisible 
in front view. 
The proximal end of me. IV is somewhat broader than that of me. Ill, 
which is due to a short, heavy process on the radial side, which carries 
the facet for articulation with me. III. The shaft, so far as it is preserved, 
is rather more slender than that of the latter and of more angular, sub- 
quadrate cross-section. The distal end has the articular surface carried 
up much higher proximally than that of me. Ill, which gives it quite a 
different appearance. The fifth metacarpal is the heaviest of them all. 
The head is made somewhat wider than the shaft by the presence on the 
radial side of a heavy, but very short projection, which articulates by a 
large facet with me. IV. The surface for the unciform is very oblique 
and concavely curved, the head of the metacarpal extending around the 
outer side of the unciform so as almost to reach the pyramidal. The 
stout shaft, the length of which cannot be determined, is trihedral in 
shape, with broad radial side, thinning to a rounded border on the ulnar 
side. As much of the shaft as has been preserved is quite straight. 
The distal articular surface is extended upward much more than in me. 
IV and receives an asymmetrical appearance from the distal production 
of the internal portion of the trochlea. 
The phalanges (PI. XXX, fig. 2) are as peculiar as the metacarpals 
would lead one to expect. Only in digit III are they all preserved, but 
apparently those of the other digits differ merely in size and relative 
width. The first phalanx is broad proximally, narrowing much to the 
distal end. The proximal facet is concave and very oblique, in conse- 
quence of which the palmar face considerably exceeds the dorsal in length. 
The distal facet is divided by a median groove into two condyles, but the 
articular surface is not carried far over upon the dorsal face and indeed is 
