37 
and passes upwards and backwards to be inserted, with the preceding ligament, into the 
back part of the interspace of the condyles. The head of the tibia sends down an an- 
cular 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. In one specimen I found the fibula 
also anchylosed to the “bia 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, 2 inches 3 lines in length ; 
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 
of bone is very narrow anteriorly, but broad and prominent on the opposite side. The 
bone becomes flattened from before backwards, and expanded laterally as it descends, 
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 adjoming toe 
having three, the next four, and the outermost five phalanges. 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 Apterya will be subse- 
quently described. The cavity of the cranium indicates the brain to have been pro- 
portionally larger than in the diurnal Struthionde. 
Of the organs of special sense, the ear, as we have already seen, resembles that of the 
larger Struthionide in the development of the external passage: the structure of the in- 
ternal organ was conformable to the typical condition of this part in Birds. 
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 
