The lower portions of the ossa quadrata are pushed somewhat
forward by this compression, assisted by two small muscles'
not exhibited ; but the situation of which may be explained
by a reference to figure 3. One of these, a small flat muscle,
arises from the septum of the orbits behind the small aperture
observed in the septum,-and passes; downward -to be
inserted upon the projecting styloid process of the qs quadra-
turn ; the second is a small pyramidal-shaped muscle arising
also from the septum, anterior to the other muscle, and passing
downwards and backwards, is inserted upon the omoi-
deum,. both muscles by their contraction pulling the* os
quadratum forwards, and thus elevating the upper mandible.
The depressors of the lower jaw, amj. th e : elevators of thé
upper jaw, therefore, act together to separate the mandibles*^
To close the mandibles, the temporal and pterygoid mus-i
cles elevate the lower jaw, assisted by two slender slip|?
marked d, d, figure which, extending forwards to the superior
maxillary bones, act- in concert by bringing them
down.
When the lateral motion is required, the great .pyramidal'
muscle on the right side pulls the extremity of the lower j aw,
to which it is attaehed backwards; the pterygoid nausClo of
the left side a t the same time powerfully assisting ^ carrying1
that side of the lower jaw inwards.
Having thus described the muscles of the mandibles, in
birds generally, and their peculiar mode of aetiom--hi the
Crossbill, I shall quote Mr. Townson’s description of the
manner in which they are made subservient to 'tbe use*öf the
bird in feeding. “ The great pine forests, such as the Hartz
in Germany, are the natural places of residence of the Cross-
beaks, and the seed of the cones of these trees-their food, and
it is to pull out the seeds from between the squamae, or scales
of the cones, that this structure is given them. Their mode
of operation is thus:—-They first fix themselves across thie cone* ’
then bring the points of the maxillae from their crossed or
lateral position, to be immediately over each other. In this
reduced compass they insinuate their beaks between the
scales, and then opening them,—not in the usual manner,
but by drawing the inferior maxilla Sideways,—force open the
scales.”:?-1
A t this stage of the proceeding the aid of the tongue becomes
necessary ; and Éhis-’orgah is-no less admirably adapted
for the service required. The os hyoïdes/ or bone of the
ton nub, has articulated to its anterior »extremity an additional
portion formed partly of bone with a homy covering, figures
6 anéî ^ letten a. In shape i t is narrow, about , three-eighths
of an inch in length, and extends fprwards and downwards,
the sidesïcufved upwards, the' distal extremity shaped-like a
stoop'/‘^rffcwliat pointed, and thin :on both ‘edges, th e proximal
extremity ending in two small ^processes? ? el ongated np-
wards and backwards above.thejartieulationJwith the.bones of
the tongue, each'process'having/ inserted upon it a slender
imiscll, b, figures 6 and 7 r extending backwards to the glofe
tis, and attached*',ti*- theses hyeides, whickmuscldsyby their
contraction, extend' and raise the!1 scoop-like »point. , Un--
derneath the articulation of this homy and grooved append-,
age is another small muscle*,’»m, figure 7 , which ùs attached a t
one éitrfirïity ta the os hyoidest, at the: other to the moveable
piece, and--by its* action as an antagonist to the upper musr
* cles, bendfe tbe cutting ipoint downwards and backwards /
while, therefore, the points'?of the.-beak press the scale from
the- bodyf êf the cbne/' thé- tbïfgue, brought forward by its
own muséjeïf1 (genio hyoMehs^y is* .enabled,* by the additional
muscles described^ to direct and-insert its-cutting sêoqp underneath
the seed, and the food thus dislodged is transferred
to the mouth ; and it will bei se®$$b^l a reference to the first
figure, that when thé mandibfesiare-separated laterally in this
operation, the bird has an uninterrupted view of the seed in