HOLLAND AND PETERSON: OSTEOLOGY OF THE CHALICOTHEROIDEA. 201 
and the material available for study, it seems hazardous to suggest that any other 
family, except that of the Chalicotheriide, is represented by the material thus far 
recovered by paleontologists. 
Since the foregoing paragraphs were written, and were on the point of being 
sent to the printer, we have received from Professor H. F. Osborn separates of a 
paper extracted from the Bulletin of the American Museum of Natural History, 
Vol. XXXII, pp. 261-274 (1913), in which he unqualifiedly accepts the view that 
the Chalicotheres constitute a superfamily of the suborder Perissodactyla, and in 
which he also erects the new genus Homoropus for the reception of T'riplopus 
amarorum Cope, which he refers to the Chalicotheroidea. 
SUBFAMILIES OF THE CHALICOTHERIID2. 
A very careful and minute study of the available material has led to the 
conviction that a subdivision of the family Chalicotheriide is necessitated. The 
subfamilies proposed are the following: 
I. The Schizotheriine. 
II. The Moropodine. 
III. The Macrotheriine. 
I. The Subfamily Schizothertine.—The type of this subfamily is the genus 
Schizotherium Gervais from the Lower Oligocene of France. With the genus 
Schizothertum we have provisionally associated from purely stratigraphic consider- 
ations the genus Pernatherium from the Eocene. Coming, as it does, from a lower 
geological horizon, it seems probable, that, when we shall have recovered enough 
of its remains to reach definite conclusions as to its foot-structure, we shall find that 
the same primitive conditions which exist in Schizotherium are represented in it 
also. 
The foot of Schizotherium shows conclusively that it had a facet on the radial 
side of Metacarpal II, for the articulation of a vestigial pollex. On the outer 
surface of Metacarpal IV is a well-defined facet for the reception of the fifth digit. 
(Cf. H. Filhol, “Observations concernant Quelques Mammiferes Fossiles Nouveaux 
du Quercy,’ Ann. des Sciences Naturelles, Vol. XVI, pp. 142-144 (1894).) In 
the possession of a fifth digit Schizotherium resembles Moropus, but the latter 
genus gives no evidence whatever of the survival in the most vestigial form of a 
first digit. The Schizotheriine are differentiated from the other subfamilies of 
the Chalicotheriide by the fact that they have retained in the structure of the 
manus evidence of their descent from a primitive pentadactyl ancestry, having 
the articulating facets for the thumb and the fifth finger. 
