THE STRUCTURE AND RELATIONSHIPS OF ANCODUS. 
485 
posterior, whUe in Oreodon this is exceeded by the transverse width. The plantar 
hook, which in the latter genus is long and well developed, is small, hardly more 
than a rudiment. On the fibular side the facets for the cuboid correspond in size, 
shape, and position to the navicular surfaces on that bone, already described. The 
distal side displays separate facets for the cuneiforms. That for the ectocuneiform 
is very large and occupies the whole dorsal half of the distal surface. There is a 
second isolated hicet for the same bone, almost circular in shape, which stands be- 
hind the principal surface and at a somewhat higher level. The mesocuneiform 
facet is very narrow, and is confined to the tibial margin of the navicular, while 
that for the entocuneiform is considerably larger, more concave and more oblique, 
being continued down upon the tibial side of the rudimentary beak. This facet is 
almost entirely plantar in position, and concealed w'hen the bone is seen from the 
front. 
The entocuneiform is of very remarkable shape, quite unlike that of any artio- 
dactyl with which I have been able to compare it, though most resembling that of 
the hippopotamus. It forms a high and very broad plate, not unlike a pisiform in 
appearance, and had it been found isolated, would have been very puzzling. Antero- 
posteriorly it is compressed and thin, but has a rugose surface. The proximal end 
is contracted to form the navicular facet, which is transversely convex. Laterally 
it articulates with the cuboid and anteriorly with the mesocuneiform, and extends 
down behind the second metatarsal, with which it has an unusually long contact. 
Distally it bears a facet for the rudimentary first metatarsal. In Oreodon the ento- 
cuneiform has an entirely different shape, being high and narrow, articulating more 
extensively with the navicular hook, but without facets for the cuboid or first meta- 
tarsal. The latter occurs in Protoreodon [fide Marsh). This element has not yet 
been identified for any of the European species of Ancodus. 
The mesocuneiform is small and stands at a somewhat higher level than the 
ectocuneiform. Though the specimen here described is of a young animal, m which 
the epijihyses are still separate, an incipient cocissification of the meso- and ectocu- 
neiforins is very plainly marked, and in the adult the two bones are doubtless as 
indistinguishabiy ankylosed as in Oreodon. In the European species the ankylosis 
of these elements is, according to Kowalevsky, subject to individual variation; m 
some specimens the two have coalesced, while in others they are separate. n e 
spcciine.i of A. mierUanus from tlie Metoiovnodoil-Ws the ect.> and mesocunei- 
forms remain separiitc. How far this difference is characteristic of the species, and 
how far subject to individual vari.ation. cannot be definitclj deeded at present 
The ectccuHdform is liigher, aamnver, and deeper than in 
that nenus tliere is a small lateral surface for the second metatarsal The proximal 
side I'iears iwo facet, for the navicular, a large one in front „f snbtriangular shape, 
and behind this a small circular and isolated facet. available the 
It is somewhat difficult to 
which this description is for the most part founded has no metatarsals 
