this subject, will demonstrate. When holding the head of
this bird in my fingers, I found that I could bring the point
of the under mandible in a line underneath, and touching the
point of the upper, but not beyond it, towards the left side ;
while on its own side; the-point passed with ease to the distance
of three-eighths of an inch. The upper mandible has
a limited degree of vertical motion .on the cranium, the su-*
perior maxillary and nasal bones being united to the‘frontal
bones by flexible bony laminae. The form, also, as well as
the magnitude of the processes of the bones of the head are
also peculiar to this bird.
The- pterygoid processes of the palatal bones are considerably
elongated downwards, as shown, at figure 8, letter a,
to afford space- for the insertion of large pterygoid muscles!
The' os omóidèum ón each side, figure '8, letter b, is strongly
articulated to the os quadratum,. rfigure 8, letter c, affording
firm support -to the moveable portion of the upper mandible*’
Létters d, d, refer to thé jugal"bone, which,' united-to the
superior maxillary bone' in front, is firmly attached by%S
posterior extremity to . the outer side-of the os quadratum $
when, therefore, the os quadratum is‘pulled’upwards and forwards
by its own peculiar muscles, to be hereafter mentioned*
the jugal-bone' on èach’ side by its pressure forwards elevates
the upper mandible.
• The inferior projecting process • of the;; os quadratum, to
which the lower jaw is articulated, in most other birds is
somewhat linear from before backwards, and compressed at
the sides, admitting vertical motion -only upwards and downwards
; the same processes in the Crossbill are spherical* as
shown at figure 8, letter c ƒ jil# iiatity in* -thëtiower jaw de~
stined to,receive this process is a hollow circular cup, figure
5, letter a the union of these two portions, therefore, forms
an articulation possessing much of the universal motion and
flexibility of the mechanical ball-and socket joint.
* The lower jaw is of great strength, the sides or plates ele-
yated, with prominent coronoid processes, figure 5, b, b, to
which, a® well as to the wholf puter surface of the plates, the
temporal muscle is attached; a n d , in a head of this bird,
which-had been,..divested’ of-all the soft parts, I,found, on
sliding the ).low<er jaw laterally upon the upper, Las performed
by the bird, that before the,coronoid process is brought into
contact with, the pterygoid on its own side* the extreme
jpoints; of the maprijbles were separated laterally to thé ex*
tent I have already mentioned,—namely, three-eighths of an’
inch.-
^ |T h e temporal and pyramidal muscle^» on the right side of
the head,,that,being, theysidet,o which the lower jaw inclined,
were .con,siderably|larger than -those! on the. left side, -as re-
presentedi in figures, .4,;|^ttersfa -and|èv and ihdife
cated by {their bulktthe great, lateral power this bird is capar
big; of ^exerting, t# fag^hereafter -..noticed.. The unusually;
la,me».sj^e^of the-.pterygoid m^Sjclhs ,on each.side was.very
*conspicubps*,figure i 2, betters Gf|| ; the fspaice-' for them being*
qbtajngd Lhy the »-gjeat. distance^to which' the^articulated extremities
of th%l°w-er jaw were removed, and th^food .of ,the-
bijd ,htei-ng small -seeds, - rendered a narrow pharynx .sufficiënte
for the. purpose of swallowing.
The muscles which depress th e viewer mandible arethre.lt
number, only one °f which, the great pyramidal, is visible,
figures ', 1 and 4, letter IÉ) This latgef and .-strong muscle'
coyers. twQs^Éher small ou$%> $hg. triangular and- square mus-J
cleS,"i;so called;; from their, peculiar- shaped' ?$ljrh@se- three*
mjisqles, ,alhpf whichjhay|£ th$ir<$ origin .$n» the*.océipltal.Lpor-
tion o f, the^..cranium, are inserted, by strong-tendons oh the!
Under and back part of-each extremity qf the lower jaw,;
behind *$,th© - cejntijq of,motion, and *$$n$equ£nfly by their sh:
multan^OjiSfc contraction ;^aisë the point'.to which they are
attached, and depress the - anterior part of th e mandible.