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articular surface is sub-reniform, convex vertically, and slightly 
encroaches upon the inferior surface. The superior surface of 
the phalanx is rough and somewhat convex transversely, and the 
inferior is concave in both directions. 
Phalanx III. 4. — This ungual phalanx, which forms an 
irregularly oval, concavo-convex plate, is broader than long, and 
does not greatly exceed in length that of its predecessor in the 
series. The plane of its proximal surface is inclined downwards 
and forwards, so that it encroaches on the under surface of the 
bone. The anterior border is broadly rounded. Two large 
vascular channels, the opening of one of which can be seen in 
fig. 6, enter just above each basal angle, and are directed for- 
wards. 
Phalanx IV. 1.—This segment has somewhat the same form 
as III. 1 on a smaller scale, the widths of the two bones at their 
middle points being as 21 mm. to 31 mm., and the lengths, as 
previously quoted, 68 mm. to74mm._ Its proximal articular sur- 
face (Pl. vi., fig. 5, TV.) is concave and subtriangular with the base 
inferior. The external angle, at the base, being more prominent 
than the internal. From each of these angles a rough, 
rounded ridge is continued forward, on the under surface, 
for a short distance. The upper surface is convex transversely, 
the inferior nearly flat, and the section at its middle nearly semi- 
circular. The distal expansion is depressed and has an articular 
surface of a form very like that of ITI. 1, except that the vertical 
depths of the two convexities of the trochlea are nearly equal. 
There is a depression on each of its lateral surfaces. 
Phalanx IV., 2,is much depressed, with a contour and form 
resembling those of III., 2, only of considerably smaller dimen- 
sions. 
Phalanx IV , 3, is similar in contour and form to III., 3, but 
much smaller. 
Phalanx IV., 4, is a slightly curved, small ungual phalanx, a 
little longer than broad; rather larger and more obtusely 
pointed than IT., 3. Just in front of the angles at the base are 
grooves which lead into vascular canals, which continue forwards 
in the substance of the bone. Smaller vascular perforations on 
both upper and under surfaces. 
The segments of IIT. can be at once distinguished by the great 
breadth and depression of all but the proximal end of the first 
phalanx. Those of IV. have a general resemblance in form to 
the corresponding elements of III., but are only about two-thirds 
the width. The great relative length, slenderness and compres- 
sion at once indicates II., 1. Ph. I1., 2, has the general contour 
characters of IV., 2, but has only about two-thirds the breadth, 
and has not the same detinite trochlea for its distal articulation 
