ull (Figure 2) it will be seen that
the maxilla sends in a plate to form the front part of the hard palate.
Behind, the hard palate is completed by the pair of palatine bones
(pal.), which conceal much of the pre- and orbito-sphenoid in the
ventral view, and which run back as ridges to terminate in two small
angular bones, the pterygoids (pt.) which we shall find represent much
more important structures in the lower vertebrata.

Section 90. The pre-maxillae and maxillae bound the sides of the
nasal passage, and it is completed above by a pair of splints, the
nasals. Along the floor of the nasal passage, on the middle line, lies a
splint of bone formed by the coalescence of two halves. It embraces
in a V-like groove the mesethmoid (nasal septum) above, and lies on
the palate.

{Lines from First Edition only.}
-Its position is indicated by a heavy black line in 4, and it is
called, the vomer bone (vo.).-

{Lines from Second Edition only.}
[In the frog it is represented by two laterally situated bones.
This is the vomer bone (vo.).]

The nasal passages are partially blocked by foliated bony outgrowths,
from the inner aspect of their walls, which in life are covered with
mucous membrane, and increase the surface sensitive to smell. The
ethmoid ends in the ethmo-turbinal (e.t.); the nasal, the naso-turbinal
(n.t.); and the maxilla, the maxillo-turbinal (m.t.). In the anterior
corner of the orbit there is a bone, the lachrymal (lc. Figure 1), which
is hidden by the maxilla in the side view of the skull.

Section 91. The lower jaw (mandible) is one continuous bone in the
mammal. Three incisors bite against the three of the upper jaw. Then
comes a canine, four premolars, and three molars, the first of which is
blade-like (sectorial tooth), and bites against the similar sectorial
tooth (last premolar) of the upper jaw. The third molar is small. The
arrangement of tooth is indicated in the following dental formula:--
I. 3.3/3.3, C. 1.1/1.1, P.M. 4.4/4.4, M. 2.2/3.3

Section 92. Attached just behind the bulla above, and passing round
on either side of the throat to meet at the base of the tongue, is the
hyoid apparatus (Figure 6). The stylohyal (s.h.), epihyal (e.h.), and
ceratohyal (c.h.) form the anterior cornu of the hyoid. The body of the
hyoid (b.h.) forms a basis for the tongue. The posterior coruna (t.h.) of
the hyoid are also called the thyrohyals.

Section 93. The following table present