No. 463.) RESTORATION OF MEGACEROPS. 423 
ever, the thrust is a vertical one, whi'e in most titanotheres, 
notably in the one under consideration, there is evidence of 
strong lateral as well as vertical motion. 
In the genus Symborodon the horn prominences are not con- 
nected by a web or bridge of bone as in this genus, Megacerops, 
which would indicate in the former an absence of lateral stress 
against the horns as though they were used more as in Rhino- 
ceros. It would be interesting to note whether a comparative 
study of the skeletons would indicate the development or 
strengthening of special muscles in forms wherein the lateral 
stress obtained. 
The titanothere skull is one of the most unique and bizarre 



= 
Fic. 3.— Head of the Megacerops restoration showing the nasal horns. 

among mammals, due to the development of the remarkable 
nasal prominences which bore the horns and the wide expanse 
of the zygomatic arch which, in the later types, became a broad 
shelf-like expansion of bone. The development of the zygo- 
mata and the height and breadth of the occiput seem to be 
directly correlated with the development of the horns, the neces- 
sity being to provide leverage for the effective use of these 
weapons. i 
In the previous titanothere restorations the nasal prominences 
are always indicated as sheathed with horn, but a glance at the 
photograph of the skull will disclose the total absence of vascu- 
lar impressions such as the horn cores of cattle and of the great 
