The =lips= are thin and mobile; the upper one is marked by a very
distinct philtrum, and otherwise is not bare.
The anterior part of the =hard palate= is prominent and smooth; on the
posterior part of this area there are two narrow depressions in the form
of a =V=, at the deep anterior ends of which the naso-palatine ducts
open. The ridges of the palate are irregular and their edges are smooth.
The posterior third or rather more of the palate is not ridged and
presents numerous orifices of ducts of the palatine glands. The mucous
membrane is often more or less pigmented.
The mucous membrane of the =cheeks= is covered with large papillæ, many
of which are long and sharp-pointed, while others are short and blunt.
There is also a series of conical papillæ on the floor of the mouth
under the lateral part of the tongue.
The =tongue= resembles that of the ox in form, but the tip is
comparatively smooth; the papillæ here are very numerous, but short and
blunt. This difference is in conformity with the dissimilarity in the
mode of prehension. The prominence of the dorsum is commonly not so
pronounced nor so sharply marked off in front as in the ox. The root is
smooth. The mucous membrane of the dorsum is often pigmented in spots.
The dental formula is the same as that of the ox. The =incisor teeth=
form a narrow and strongly curved arch. The crowns are long and narrow;
their labial surfaces are strongly convex and end at a sharp edge which
is used in cropping the grass. The roots are more firmly embedded than
in the ox.
The =cheek teeth= resemble those of the ox. There is a thinner layer of
cement, which is usually black.
The average periods of eruption of the teeth are indicated in the
subjoined table.
TEETH TEMPORARY PERMANENT
I_{1}. At birth or first 1 to 1½ years
week
I_{2} First or second week 1½ to 2 years
I_{3} Second or third week 2½ to 3 years
I_{4} Third or fourth week 3½ to 4 years
──────────────────────────────────────────────────────────────
P_{1} 2 to 6 weeks. 1½ to 2 years
P_{2} „ „
P_{3} „ „
──────────────────────────────────────────────────────────────
M_{1} 3 months (lower), 5 months (upper)
M_{2} 9 to 12 months
M_{3} 1½ to 2 years
[Illustration: