01 apteryx australis - University of Texas Libraries

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and passes upwards and backwards to be inserted, withthe preceding ligament, into the
back part of the interspace of the condyles. The head of the tibia sends down an angular
ridge posteriorly :the shaft of the bone is rounded, slightly compressed, converging
to a ridge externally, to which ridge the fibula is attached in two places, beginning half
an inch below the head of the fibula, and continuing attached for 10 lines ; then again
becoming anchylosed, after an interspace of 9 lines. Inone specimenIfound the fibula
also anchylosed to the tibia by its expanded and thick proximal extremity :it quickly
diminishes in size as it descends, and gradually disappears towards the lower fourth of
the tibia. The distal end of the tibia presents the usual trochlea form, but the anterior
concavity above the articular surface is in great part occupied by an irregular bony
prominence.
There is a small cuneiform tarsal bone wedged into the outer and back part of the
ankle-joint. The anchylosed tarso-metatarsal is a strong bone, 2inches 3 lines inlength ;
the upper articular surface is formed by a single broad piece. The original separation
of the metatarsal bone below into three pieces is plainly indicated by two deep grooves
on the anterior and posterior part of the proximal extremity : the intermediate portion
ofbone is very narrow anteriorly, but broad and prominent on the opposite side. The
bone becomes flattened from before backwards, and expanded laterally as itdescends,
and divides at its distal extremity into three parts, with the articular pulleys for the
three principal toes.
The surface for the articulation of the fourth, or small internal toe, is about half an
inch above the distal end, on the internal and posterior aspect of the bone. A small
ossicle, attached by strong ligaments to this surface, gives support to a short phalanx,
which articulates with the longer ungueal phalanx.
The number of phalanges in the other toes follows the ordinary law, the adjoining toe
having three, the next four, and the outermost fivephalanges. The relative size and
the forms of these bones are shown in the figures of the skeleton (Pl. VIII.).
Organs of Sense.
The requisite particulars regarding the nervous system of the Apteryx will be subsequently
described. The cavity of the cranium indicates the brain to have been proportionally
larger than in the diurnal Struthionidæ.
Of the organs of special sense, the ear, as we have already seen, resembles that of the
larger Struthionidæ inthe development of the external passage :the structure of the internal
organ was conformable to the typical condition of this part inBirds.
The eye, on the contrary, presented a remarkable deviation from the construction
which characterizes the feathered class, in the total absence of the pecten or marsupium.
We may conceive that this modification relates to the nocturnal habits and restricted
locomotion of the present singular species. The eye- ball is relatively much smaller