Paleontology. 167 
restricted to the Ruminants, and appear under three 
different forms or types — namely. solid, as in antelopes ; 
hollow, as in sheep ; and deciduous, as in deer. Now, 
in each of these divisions we have a tolerably complete 
paleontological history of the evolution of horns. 
The early ruminants weie altogether hornless (Fig. 60). 
Fig. 60.—Skull of Oveodon Culbertsoni. (After Leidy.) 
Then, in the middle Miocene, the first antelopes ap- 
peared with tiny horns which progressively increased in 
size among the ever-multiplying species of antelopes 
until the present day. But it is in the deer tribe that we 
meet with even better evidence touching the pro- 
gressive evolution of horns; because here not only 
size, but shape, is concerned. For deers horns, or 
antlers, are arborescent ; and hence in their case we 
have an opportunity of reading the history, not only 
of a progressive growth in size, but also of an increasing 
development of form. Among the older members of 
the tribe, in the lower Miocene, there are no horns at 
