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1908.] Structure and Relationships of the Labyrinth. wis 
That is to say, it is short, and the tube is wide in proportion to its length. 
The lagena, /., is large, and at the tip the cochlea ends in a little nipple- 
shaped projection which is peculiarly characteristic of the labyrinth of the 
ostrich and rhea. The tegmentum vasculosum, ¢.v., that curious plexus of 
parallel venous spaces, is found in the emu, as it has been in all other birds 
hitherto examined, with the single exception of the ostrich. According to 
Retzius, it is found in at least some reptiles, and the present writer has found 
it in the apteryx. Its apparent absence in the ostrich is, therefore, most 
remarkable, and it may be that it is present in a modified form, though the 
writer was unable to find even a trace of it in three different specimens of the 
Masai ostrich. In the emu, as stated above, the tegmentum vasculosum is 
clearly marked, and has an appearance similar to that found in the rhea, but 
the parallel venous spaces are fewer in number, and rather wider apart than 
in the latter. 
The recessus perilymphaticus, 7.p., that large cavity which opens out of the 
scala tympani of the cochlea, is well developed in the emu as in the other 
ratite birds. It is, however, more oval in shape than in the ostrich and rhea, 
in which it bears some resemblance to a sack with corners. On the lower and 
anterior surface of the perilymph recess is the round window, which is oval 
in shape, as in other birds and in reptiles. In the emu, the round window is 
of considerable size, larger, for example, than the oval window, fo. At the 
opposite end, that is, at the upper posterior portion of the perilymph recess, 
is the aqueductus perilymphaticus, dp. The latter leaves the perilymph 
recess directly and, after a short course of 1 or 2 mm., opens into the cranial 
cavity. Its disposition, therefore, is like that found in the ostrich, the rhea, 
the common fowl, the tinamou, and some other birds. In the crow, the night- 
heron, and many of the carinate birds, the aqueductus perilymphaticus opens 
eut of the posterior wall of the perilymph recess, and instead of passing 
directly towards the cranial cavity, it curves upward in contact with the 
posterior wall of the perilymph recess for about 2 mm., and then opens into 
the cranial cavity. 
Pigment is not found in the labyrinth of the emu, at least in sufficient 
amount to be seen by the eye, even when the organ is magnified to ten times 
its natural size. In this respect, therefore, it differs from those of the ostrich, 
the rhea and the tinamou. 
Otoliths of considerable size are found in the emu; they occupy similar 
positions as do those in birds generally, and are similar to them in shape. In 
the vestibule there are two of these crystals, o., and they lie in the utricle 
immediately behind, and internal to, the openings of the superior and 
horizontal ampullze into that cavity. They are flattened from above 
28 2 
