14 Dr. A. A. Gray. On the Anatomical [June 1, 
downwards. The remaining otolith is found in the lagena, X., and is, as is 
common in birds, saddle-shaped, with the concave surface facing downwards, 
Thus the otoliths of the emu are very similar in position and shape to those 
found in the rhea. 
The Membranous Labyrinth of the Rhea (Rhea Americana). 
(Plate 20, fig. 6.) 
As the labyrinth of the rhea has already been described, there is no need 
to give a general description of it here. But for the sake of comparison a 
representation of a portion of the organ is shown. 
It will be noticed that the otoliths, both in the vestibule and in the 
lagena, o. and /., are very similar to those of the emu. The cochlea is more 
bulbous at the inner portion than is that of the emu, but the nipple-shaped 
termination of the organ is present, though it has been broken in the course 
of preparation ; the place where it has been broken off is clearly seen. 
The perilymph recess, 7.p., 1s large in the rhea, and is sack-shaped as in 
the ostrich, rather than oval as in the emu. The round window, /7., is 
shown at the lower, outer, and anterior portion of the perilymph recess; it 
is large and has the form of a long ellipse. : 
Pigment is present in the form of minute granules, and is fairly abundant 
in amount, thus giving a speckled appearance to the perilymph recess. 
It is almost entirely confined to the perilymph recess, the distribution being 
similar to that found in the tinamou, whereas in the ostrich pigment is 
found over the surface of the perilymph recess and also over the adjacent 
surface of the cochlea. 
The Membranous Labyrinth of the Penguin (Spheniscus demersus). 
(Figs. 7, 8, and 9.) 
The labyrinth of the penguin is large, measuring 16°5 mm. from the vertex 
of the superior canal to the tip of the cochlea. The cochlea measures 
4-5 mm. from the anterior margin of the oval window to the tip, and the 
tube of the cochlea is 2 mm. in diameter at the level of the oval window. 
The vestibule measures 4 mm. in its greatest diameter, and the major axis 
of the oval window is 1°75 mm. in length. 
The superior canal measures 7 mm. in internal, and 10°5 mm. in external 
diameter. The height of the vertex of the canal above the vestibule is 
7-5 mm., and the diameter of the tube of the canal at the vertex is rather 
less than 155mm. The posterior canal measures 4°5 mm, in internal, and 
7 mm. in external diameter. The height of the vertex of the canal above 
