28

8

of the os quadratum obliquely forwards to the lower and posterior margin of the external
coronoid depression : a strong posterior ligament descends from the ex-occipital process
to the posterior angle of the jaw. These strong ligaments are an essential part of the
mechanism of a beak which is destined to be forcibly thrust into the ground, and used
in a variety of ways, to overcome considerable resistance.

The posterior expanded surface of the palate is quite smooth in the Apteryx, as in
the larger Struthionidae, in which the ridges and papillae, commonly present in other
birds, are altogether absent.

The tongue¹, as was conjectured by Mr. Yarrell, is short much shorter indeed than the
interspace of the united rami of the lower jaw ; it nevertheless presents a greater rela-
tive development than in other Struthious birds. It presents a compressed, narrow,
elongated, triangular form, with the apex truncate and slightly notched ; the lateral and
posterior margins entire : it is 8 lines in length, 4 lines broad at the base, 1 line across the
apex. The anterior half consists of a simple plate of a white, elastic, semitransparent,
horny substance, gently concave above ; behind this part, the exterior covering, which is
lost in, or blended with, the horny plate, gradually becomes distinct, and assumes the
character of a mucous membrane, and is pitted with several very minute glandular fora-
mina : this membrane is reflected over the posterior margin of the tongue, forming a
crescentic fold, with the concavity towards the glottis ; but here, as well as on every
other part of the tongue, it is devoid of spines or papillae. This fold can be brought
back by the retractors of the os hyoides, so as to cover the glottis ; in which movement the
uro-hyal process plays in a cellular sheath beneath the larynx, and its office seems to be
to give steadiness to the protractile and retractile movements of the tongue. The su-
perficial and principal protractor of the tongue represents the genio-hyoideus, its two
lateral halves being separated and removed from the symphysis to within an inch of the
angle of the jaw, whence its fibres pass almost directly backwards, and converge, to be
inserted into the extremity of the bony cornu of the os hyoides. The mylo-hyoideus arises
from the inner side of the lower jaw, commencing posteriorly about an inch from the
angle, and extending forwards to within the same distance of the symphysis ; the fibres
become gradually fewer as they are placed more forwards ; they meet to be inserted at
a middle tendinous line posteriorly, and are separated anteriorly by a tendon about a
line in breadth : these tendons are attached to the body of the os hyoides, and retract it :
a few tendinous threads connect also the posterior margin of the muscle with the ante-
rior part of the upper larynx. On the removal of this muscle two deeper-seated pro-
tractors of the tongue are brought into view ; they arise by a very thin aponeurosis from
near the angle of the jaw, and pass directly backwards, to be inserted into the base of
the cornua. These muscles adhere closely to the membrane, filling up the interspace of
the rami of the lower jaw. The cartilaginous extremities of the cornua of the os hyoides
curve upwards, and terminate about a line behind the angles of the jaw.

¹ Pl. III. Figg. 1 c & 2.