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The relations of the modifications of the skull of the Apteryx to its peculiar habits 
and kind of food are well marked and very easily traced; those which concern the 
maxillary portions have already been noticed in the account of the digestive system, and 
I need only add here that the anchylosed condition of all the parts concerned in the 
formation of the upper mandible is more complete than in the larger Struthionide, and 
relates to the greater force with which the beak is used in obtaining the food. 
The nocturnal habits of the Apteryz, combined with the necessity for a highly deve- 
loped organ of smell, which chiefly compensates for the low condition of the organ of 
vision, produces the most singular modifications which the skull presents, and we may 
say that those cavities which in other birds are devoted to the lodgement of the eyes, 
are here almost exclusively occupied by the nose. 
The spinal column is relatively stronger, especially in the cervical region, than in the 
larger Struthionide : it consists of fifteen cervical, nine dorsal, and twenty-two remaining 
vertebre in the lumbar, sacral, and caudal regions. 
The dorsal vertebre are arranged in a straight line, and slightly increase in breadth 
to the seventh ; the transverse processes of the eighth and ninth suddenly diminish. The 
third, fourth, fifth and sixth dorsal vertebre are slightly anchylosed together by the con- 
tiguous edges of their spinous processes ; the seventh, eighth and ninth are overlapped 
by the iliac bones ; but notwithstanding this partial anchylosis, the synovial articula- 
tions, both between the bodies and oblique processes, are retained in all the dorsal 
vertebra, and a slight, yielding, elastic movement is permitted between those vertebre : 
the body of the last dorsal vertebra is anchylosed to the sacrum. The breadth of the 
bodies of the dorsal vertebre diminishes, and their length increases very gradually from 
the first to the fourth; thence the bodies become broader and shorter in the same 
degree to the sacrum, A short obtuse process is sent off obliquely forwards from the 
inferior surface of the body of each of the first four dorsal vertebre ; the corresponding 
surface of the succeeding ones is smooth and slightly concave from side to side, The 
articulation between the bodies is by the adaptation of a surface slightly concave in the 
vertical and convex in the transverse direction at the posterior end of one vertebra 
to opposite curves at the anterior end of the succeeding one. Close to the anterior sur- 
face on each side there is a hemispherical pit for the reception of the round head of the 
rib: this articular pit is supported on a process representing the inferior transverse 
process, except in the three middle dorsal vertebre. The transverse processes are 
broad, flat, and square-shaped, with the anterior angle obliquely cut off to receive the 
abutment of the tubercle of the rib, except in the second and third, in which a small 
process is sent down for the same purpose from the under surface of the transverse 
process: the transverse processes of the three last dorsal vertebre ubut against the 
under or inner surface of the ilia, and are probably anchylosed thereto in old birds. 
The nerves issue from the interspaces of the vertebre above the articulation of the heads 
of the ribs. The transverse processes are not connected together by extended long 
