The =third tarsal= bone (Os tarsale tertium, third or great cuneiform)
resembles the central, but is smaller and triangular in outline. It is
situated between the central above and the large metatarsal bone below.
It possesses two surfaces and three borders.
The =superior surface= is concave, and is crossed by a non-articular
depression which divides it into two unequal facets; it articulates with
the central tarsal. The =inferior surface= is slightly convex, and rests
on the large metatarsal bone; it has an extensive central rough
excavation. The =anterior= or =dorsal border= is convex and bears a
rounded ridge on its inner part. The =internal border= is deeply notched
and has a small facet for the second tarsal on its anterior part. The
=external border= is also divided by a notch into two parts, and bears
two diagonally opposite facets for articulation with the fourth tarsal.
In some cases there is a facet for the inner small metatarsal bone.
[Illustration:
FIG. 85.—CROSS-SECTIONS OF METACARPAL AND METATARSAL BONES OF HORSE.
(After Schmaltz, Atlas d. Anat. d. Pferdes.)
]