1908.] Structure and Relationships of the Labyrinth ‘511 
of one comparatively large crystal and not of a collection of minute granules 
as does the large otolith in the saccule. 
The Membranous Labyrinth of the Emu (Dromeeus novee-hollandie). 
(Figs. 4 and 5.) 
The labyrinth of the emu is, as might be expected, a large one, larger 
indeed, than that of any bird that has been examined, except the ostrich. 
It measures 17°5 mm, in its greatest length from the uppermost point on 
the superior canal to the tip of the cochlea. The cochlea measures 4 mm, 
from the anterior margin of the oval window to the tip of the organ. The 
diameter of the tube of the cochlea immediately in front of the oval window 
is rather more than 2°5 mm. 
The longest diameter of the vestibule is 4 mm. and the length of the major 
axis of the oval window is 2 mm. 
The superior canal measures rather more than 8°5 mm. in internal, and 
11°5 mm. in external diameter. The height of the vertex of the canal above 
the vestibule is 9°5 mm. and the diameter of the canal at the vertex is 1:25 mm. 
The posterior canal measures 5 mm, in internal, and 7°5 mm, in external 
diameter. The height of the vertex of the canal above the vestibule is 
4-5 mm., and the diameter of the tube of the canal itself is 1:25 mm. The 
horizontal canal has internal and external diameters of 5 mm. and 7°5 mm. 
respectively. The height of the vertex of the canal above the vestibule is 
rather more than 3°5 mm, and the diameter of the tube of the canal itself at 
the vertex is 1:25 mm. 
The labyrinth of the emu presents considerable similarity to those of the 
other ratite birds which have been examined by the writer, viz., the ostrich, 
the rhea and the apteryx. The similarity is much more pronounced between 
the emu, ostrich and rhea, than between any of these and the apteryx. 
The semicircular canals in the emu are well curved, there being none of 
the angularity which is found to a certain extent in the apteryx alone among 
birds. The superior, s., is the largest of the three canals and is of the 
“drooping” type. The perilymph space is well marked in all the canals and 
the criste acustice of the ampulle are “simple” in character. There is no 
approximation to a channel of communication between the horizontal and 
superior canals such as is found in some of the carinate birds. In these 
respects the labyrinth of the emu agrees with those of the other ratite birds. 
In the labyrinth of the emu, as in those of the ostrich and apteryx, there is 
no communication between the posterior, y., and horizontal canals, h., at 
the point at which they cross one another. This arrangement is different 
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