Chapter M

Length ·178
Width of proximal surfaces (transverse) ·032
Width of proximal surfaces (antero-posterior) ·019
Transverse diameter of shaft ·022
Antero-posterior diameter of distal articulation ·018
Transverse diameter of distal articulation ·018

_The _tarsus_._--The _astragalus_ (Plate IX., Fig. 5) has the condyles asymmetrical and divided by a deep groove; the head is narrow, with the neck elongate. The face for the cuboid is small, and confined to the external border.

The _calcaneum_ (Plate IX., Fig. 4) is long and compressed, with its upper and lower margins straight and nearly parallel; its tuberosity is large. The face for the cuboid is small.

The _navicular_ (Plate IX., Fig. 6) is proportionately longer and narrower than it is in the modern horse. The internal and middle cuneiforms were probably separate.

_Metatarsals_ (Plate IX., Fig. 7).--Three in number. Are very much shorter proportionately than in the modern horse. In shape they are compressed and arched forward. The distal ends are flattened vertically, arched forward, and deeply grooved in the middle.

The _phalanges_ (Plate IX., Fig. 7) are very short, rather stout, and very smooth and convex above.

The ungual phalanges are very thin and crescent shaped.

_Measurements._

ASTRAGALUS.

M.
Greatest width ·029
Greatest length ·022
Length of navicular facet ·017
Width of navicular facet ·012
Length of tibial trochleæ externally ·016

CALCANEUM.

M.
Total length ·058
Total width ·019
Depth in front ·022
Length of heel ·035
Depth of heel ·018
Length of cuboid facet ·014

NAVICULAR.

M.
Width ·009
Length ·010

PHALANGES.