B. NATURAL HISTORY. 109 
and concave superior outline posteriorly, and by the presence of a 
massive horn core on each side of the front, whose outer face is 
continuous with the inner wall of the orbit, as in the Loxolophodon 
cornutus. It stood above the eye in life, and diverged from its 
fellow so as to overhang it. In the specimen, which was fully 
adult, they were worn obtuse by use—length, about eight inches ; 
thickness, three inches. The molar teeth differ from those of Ti- 
tanotherium Proutii in having cross crests extending inward from 
the apices of the outer chevrons, each of which dilates into a T- 
shape near the cones. 
The third species is referred to the new genus Symborodon un- 
der the name of S. acer. It has overhanging eyebrows and the 
vertex little concave ; but the nasal bones are greatly strengthened, 
and support on each side near the apex a large curved horn-core 
of ten inches in length with sharply compressed apex. These 
horns diverge with an outward and backward curve, and when 
covered with their sheaths must have considerably exceeded a foot 
in length. This was a truly formidable monster, considerably ex- 
ceeding the Indian rhinoceros in size. 
The fourth species is allied to the last, and has well developed 
superciliary crests without horns. ‘The latter are situated well 
anteriorly, and are short tubercles not more than three inches in 
height. They are directed outward and have a truncate extremity. 
The type individual is of rather larger size than those of the other 
species. There are several crania referrible to the three now 
named. The present one has been named Symborodon helocerus. 
Other species based upon crania without mandibles were referred 
to the genus Symborodon. 
These animals show true characters of the Perissodactyla in 
their deeply excavated palate, solid odontoid process, third tro- 
chanter of femur, which has also a pit for the round ligament, in 
the divided superior ginglymus of the astragalus, etc. 
{Printed at the SALEM Press, March, 1874.] 
