Sinclair: typotheria of the santa cruz beds. 
3i 
seous ridge. Proximally, the shaft is expanded both antero-posteriorly and 
transversely, with the oval surface for the tibia terminal. Distally, the 
fibula is in lateral contact with the tibia by a broad rugose surface. In- 
ternally, the distal end articulates with the outer astragalar crest by a cres- 
centic, plane facet, while distally a broad, antero-posteriorly concave surface 
is in contact with the calcaneum. The peroneal groove is quite distinct. 
The pes (PI. V, figs. 1, 2, 5-8, 10) is tetradactyl and paraxonic, the 
median digits are of approximately the same size and the lateral digits 
reduced. The hallux is wanting. The astragalar trochlea is long, 
moderately deep, with the crests sharp and equally developed. The neck 
is long and the head globular. The ectal facet is dumb-bell shaped, wider 
proximally than distally and strongly concave in proximo-distal section. 
The sustentacular facet is a flattened oval in outline, convex in all diam- 
eters and is supported largely by the neck of the astragalus. The fibular 
and internal malleolar facets, on the lateral surfaces of the body of the 
astragalus, are vertical, and the entire body is approximately symmetrical 
to the vertical plane, differing in this respect from Hegetotherium (cf. Pis. 
11, fig. 1 9; V, fig. 1). The most striking feature of the calcaneum is 
the large fibular facet, which is almost as large as the ectal surface. Both 
are strongly convex proximo-distally and slightly convex transversely. 
The sustentaculum is heavy and deep in the dorso-plantar diameter, with 
its free margin grooved. The sustentacular facet is oval in outline and 
concave. The cuboidal facet is much less deeply concave than in Hege- 
totherium. Unlike that genus, there is no articulation between the cal- 
caneum and the navicular. The tuber is moderately elongated and rather 
heavy, supporting a large rugose area distally. The navicular is deeply 
cupped proximally for the head of the astragalus, while distally it sup- 
ports three facets for the cuneiform bones (PI. V, fig. 8). It may be 
readily distinguished from that of Hegetotherium (PI. II, fig. 16) by the 
small size of the mesocuneiform facet and the absence of an articular 
surface for the calcaneum. The external cuneiform facet is subcircular in 
outline and almost plane, that for the mesocuneiform oval and slightly 
convex in all diameters, while the facet for the internal cuneiform is cres- 
centic and convex in all diameters. Externally, the navicular is in con- 
tact with the cuboid by a large reniform facet, slightly convex in dorso- 
plantar section and concave proximo-distally. The internal plantar 
tuberosity is quite long, perhaps representing a coossified sesamoid, such 
