scott: toxodonta OF THE SANTA CRUZ beds. 
1 7 1 
The calcaneum is short and massive. The tuber, which is very heavy, 
broadens gradually to the free end, which is roughened and has on the 
plantar surface a shallow tendinal sulcus, somewhat as in the Artiodac- 
tyla, though the groove is not median, as it is in the latter, but near the 
internal side. The fibular facet is very large and forms a broad, heavy 
prominence, on the tibial side of which is an oblique, convex facet for the 
astragalus ; this latter surface is produced proximally considerably beyond 
that for the fibula. While of only moderate size, the sustentaculum is 
very thick and prominent ; its astragalar facet is of irregularly oval shape 
and nearly plane. The distal end of the calcaneum is also very heavy 
and bears a broad, slightly saddle-shaped surface for the cuboid, which 
is concave planto-dorsally and convex transversely ; internal to this is a 
small facet for the navicular. 
The navicular is low proximo-distally and of subcircular shape ; its 
greatest proximo-distal height is through the facet for the large ectocunei- 
form, while the internal portion is hardly half as high. From the plantar 
side is given off a very low tuberosity, which appears to be the remnant 
of the usual navicular hook. On the proximal end, the astragalar surface 
is simply concave in both directions, narrowing toward the plantar side, 
and on the fibular side is a small, articular projection, formed by the con- 
joined surfaces for the calcaneum and cuboid, the former presenting later- 
ally and the latter obliquely distally. The distal end is occupied chiefly 
by the large facet for the ectocuneiform, which is oblique, sloping down 
toward the tibial side and contracting much toward the plantar side. The 
facet for the mesocuneiform, which is much smaller, is also oblique, slop- 
ing in the opposite direction and forming an obtuse angle with the ecto- 
cuneiform facet. 
The meso- and entocuneiforms are fused together, though the limits of 
each element may still be made out. The entocuneiform is a small, irreg- 
ular, nodular bone, which has no contact with the navicular and carries 
only one facet, a small, oblique surface on the distal end for the head of 
the second metatarsal. The mesocuneiform is much larger and bears a 
large, slightly convex surface for the navicular and interlocks with the 
ectocuneiform in a curiously intimate and complicated manner. Dorsally, 
there is a large concavity, into which fits a convexity on the tibial side of 
the ectocuneiform and on the plantar side the mesocuneiform sends a 
small shelf-like projection underneath the ectocuneiform and this shelf has 
a small, concave, obliquely proximal facet for the latter. 
