771e Extinct American Rhinoceroses and their Allies. [December, 
state of things commences in the extinct species of Kansas, the 
Aphelops fossiger. 
Fic. 3.—Aphelops weer Cope, skull from hi one-sixth natural size. 
oup Fork beds of Kans 
In the bones of the skeleton, modifications o iecteccinc those 
of the cranium and dentition may be observed. The femur of the 
species of the earlier formations may be readily distinguished 
from that of those of the later Tertiaries by the forms of both 
the extremities. In the Aceratheria this bone resembles that of 
the tapirs in the form of the great trochanter, This process is 
` produced at its external border, has a recurved apex, and encloses 
a deep trochanteric fossa. In Aphelops it is precisely as in Rhi- 
nocerus, obliquely truncate externally, without prominent apex or 
well marked fossa. In the Aceratheria the inner crest of the 
rotular groove is but moderately prominent; in Aphelops and 
Khinocerus it is greatly developed. 
The succession of development of the line of the Rhinoceride 
is now not difficult to trace, and I give the following diagram in 
explanation of it. 
Celodonta 
/ 
Rhinocerus. Atelodus. ə 
i 7 
Ceratorhinus. 
Aphelops. 
| 
Zalabis, Aceratherium. Diceratherium. 
| Iti is evident that the descent diverged at a comparatively late _ 
d of geological time into two lines, which are represented at 
rese it day by th he > African and Indian species reapepsinely 
