77ie Extinct American Rhinoceroscs and their Allies. (December, 
state of things commences in the extinct species of Kansas, the 
Aphelops fossiger. 
Fic. 3.—Aphelops fossiger Cope, skull from below, one-sixth natural size, 
Loup Fork beds of Kansas. 
In the bones of the skeleton, modifications accompanying 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 Aceratherta 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 Rhz- 
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 
Rhinocerus it is greatly developed. 
The succession of development of the line of the R/inoceride 
is now not difficult to trace, and I give the following diagram in 
explanation of it. 
Celodonta 
x 
Rhinocerus,  Atelodus, 
\ a 
Ceratorhinus. 
| 
Aphelops. 
Zalabis, Aceratherium. Diceratherium, 
‘% | a 
It is evident that the descent diverged at a comparatively late 
period of geological time into two lines, which are represented at 
the present day by the African and Indian species resnectivelv 
