01 apteryx australis - University of Texas Libraries

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tures a narrow ridge is continued forwards along the middle line of the palatal surface
of the beak to its deflected extremity :a mesial groove, corresponding with the above
ridge, runs along the flattened upper surface of the elongated myxa of the lower mandible.
There is the same structure on the inner surface of the upper and lower mandible in
the Ostrich and Rhea. In these, however, the palatal surface of the upper mandible is
slightly concave ;but in the Apteryx the opposed surfaces of the upper and lower mandibles
produce, when pressed together, uniform and entire contact, and, as Mr. Yarrell
has observed, are well adapted for compressing or crushing such substances as may be
selected for food : the coadapted ridge and groove above described must add somewhat
to the power of retaining such substances. Tojudge from the feeble development of the
muscles of the jaw, and their disadvantageous place of insertion, the force of the nip of
the mandibles, however, cannot be very great ; and with this knowledge of the structure
of the bill,Iwas the less surprised to find large soft-bodied Lepidopterous larvæ
entire in the stomach ofMr.Bennett's male Apteryx.
There are two small temporal muscles, one superficial, the other deep-seated, which
cross each other obliquely : the superficial and posterior muscle is 4 lines broad and 1
inch long :itis inserted by a round tendon into the coronoid edge, and by fleshy fibres
into the external depression beneath that edge, extending as far forwards only as twothirds
of an inch from the joint of the jaw. The deep-seated temporal muscle sends its
fibres to be inserted more vertically into the coronoid margin. A masseter, which is
connected with a remarkably strong orbicularis palpebrarum, is inserted still nearer the
Joint, below the fossa for the insertion of the temporal muscle, and external to it.
There is a fourth muscle employed in closing the bill,having a similar direction of its
fibres to those of the masseter, but situated on the inside of the temporal muscles : it
extends from the pterygoid bone downwards, to be inserted fleshy into the inside of
the coronoid margin of the lower jaw. This bone admits of slight protraction and
retraction, the muscles performing which are the external and internal pterygoid, on
each side. The external pterygoid arises by a broad and flat tendon from the pterygoid
plate, external to the posterior nares, and expands as it proceeds backwards and
outwards, to be inserted into the inflected posterior angle of the lower jaw. The internal
pterygoid arises from the body of the sphenoid, behind the posterior nares, and contracts
as it proceeds more directly outwards to be inserted into the angle of the lower
jaw, above the preceding. The billis opened by the analogue of the biventer maxillæ,
which is here a stout, short, square-shaped fleshy muscle, deriving its origin from the
ex-occipital process, and descending vertically, to be attached to the broad posterior
angle of the lower jaw:from its close situation to the centre of motion this muscle can
divaricate the tips of the mandibles about two inches. The movements of the jaw are
regulated, and its joints strengthened, by several ligaments : one of these ligaments is
interarticular, and passes directly between the jaw and os quadratum, in the interspace
of the double condyle : another is external, and passes from the upper and outer angle