Page 451 - My FlipBook

TEETH OE THE VERTEBRATA. 461 ;

eating Mammalia. It includes two divisions—one in which the superior
canines are normal and without the vertical angles and inferior flanges
to tlie mandible ; and another, " sabre-tooth division," wherein the
superior canines are enormously enlarged, denticulate, and protected
by inferior flanges of the rami.
The first of these groups or sub-families is the more generalized, and
embraces all the existing cats or those animals popularly known as lions,
Fif4. 242.

Pogiinodon plaiyeopis, Skull, less than two-fifths natural size (^after Cope): 2, ", 4, second, third, and
fourth premolars, and 1, first lUoUir of lower jaw F G, post-glenoid foramen P JP, post-parietal
; ;
foramen.
tigers, leopards, panthers, etc. Five genera have been established in this
division on characters of the teeth and orbit. It is here that the domestic
cat belongs, and its dentition may be taken as a good average represen-
tation of that of the sub-family.
The dental formula in this animal is I. , C. y, Pm. |^, M. ^ =; 30.
f
The incisors are rehitively small, and are disposed almost transversely
across the front of the jaw. The first premolar above is a small, single-
rooted tooth, and is situated at a considerable distance from the canine,
which has tlie usual form and proportions of that tooth in the C'arnivora
generally. The second is larger and two-rooted, while the fourth
or upper sectorial is decidedly the largest tooth of the superior series
it has three external cusps united into a blade, and a small internal
tubercle. The single mokir is very small and functioidess, being
placed internal to the posterior part of the large sectorial. In the
lower jaw the premolars are proportionately large, having two fangs
and posterior accessory cusps. The sectorial is specialized, and con-
sists simply of two cusps forming a trenchant blade ; both the heel
and internal tubercle are absent.
The lynxes have one less premolar upon each side above than the cat,
and for this reason are ])Iaced in a distinct genus. In the flat-headed
cat and the fishing cat the orbit is completely encircled by bone—an
unusual occurrence in this familv. In both, the number of teeth is the