BUNOTHEEIA. 
77 
convex, the internal surface for the inner malleolus flattened, and at right 
angles with the preceding, hut the outer articular surface presents a triangu¬ 
lar flattened form, and, instead of being bent down parallel with the inner 
articular surface, slopes aAvay at a very open angle from the upj)er surface, 
receiving the articular surface of the fibula so as to sustain its vertical 
pressure. . . . This form of astragalus is also characteristic of the Koala, 
Petaurists, Dasyures, and the Pedimanous Marsupialia.” 
In one species, where the cuboid bones are preserved, it is evident 
that the distal end of the astragalus articulated with this as well as with the 
navicular bone, although tlie facet of the astragalus is single and continuous. 
As the extensive transverse distal astragalar face is characteristic of all the 
species where it is preserved, the contact of tlie cuboid and astragalus is 
probably common to all of this division. There is no elongation of tlie 
navicular; it is, on the contrary, very short, since the astragalus projects 
beyond the calcaneum (in the genera where they have been observed). The 
cuboid is, on this account, rather elongate, but not remarkably so. There 
were five toes in the hind feet of some of the species. The ungues in some 
of the genera are compressed and acute. In the genus Synoplotlierimn^ from 
the Bridger Eocene, I found one of the claws to be broad and flat, so as to 
be subungulate. I found an ungueal j^halange in Kew Mexico, probably 
belonging to a species of this group, which presented a similar, though less 
expanded, form. I have every reason for believing that there were five 
toes on the hind foot of Stypoloplius liians and a second species. 
The characters now adduced lead to the following conclusions as to 
the systematic position of these animals. 
The small size of the cerebral hemispheres and the very slight indica¬ 
tion of convolutions, refer this group to the Lissencephalous or Lyence- 
phalous Mammalia. The characters presented by our crania are borne out 
by those exhibited by tlie Arctocyon p?'ima;vus, De Blainv., from the Lower 
Eocene or Suessonian beds of Erance. Professor Gervais* has discovered 
that the olfactory lobes are large, and project far beyond the hemispheres, 
while not only the cerebellum but also probably the corpora quadrigemina 
were exposed behind. We are therefore restricted, early in the inquiry, to 
^Xouvelles Archives du IMuseum, 1870, p. 150. 
