1908.| Structure and Relationships of the Labyrinth. Pout ae 
perilymph recess, 7.p., is seen behind the cochlea, c. The round window is barely 
visible. On looking through the perilymph recess to its upper and inner wall the 
narrow opening of the aqueduct of the perilymph, ¢.p., is seen. The black patches 
on the walls of the. perilymph. recess are due to hemorrhages. -No pigment is 
visible. The nipple-shaped termination to the cochlea is seen below the lagena, /, 
a.p., ampulla of posterior canal, 
PLATE 19, Fie. 5. 
Portion of the Right Membranous Labyrinth of the Emu, Dromeus nove-hollandic. 
x 10$ca. Taken by transmitted light and viewed from the outer aspect. One 
of the otoliths of the utricle is seen as a sharply defined black structure, o., at the 
top right-hand corner. The parallel venous spaces of the tegmentum vasculosum, 
t.v., are well shown. The helicotrema, /.c., is seen as an oval opening about 
three-quarters of the way along the cochlea, ¢, to the right, with a large vein 
passing through it. A saddle-shaped otolith is present in the lagena, 7. The 
dise-shaped footplate of the columella is seen in its natural position in the oval 
window, 7.0., and it is to be noted that the latter is situated in the cochlea some 
little distance from its beginning, and is in this respect different from those of the 
reptiles and mammals. The perilymph recess, the round window, and aqueduct 
of the perilymph are seen as described in Plate 4, but are more highly magnified, 
Prar 20. Fie. 6: 
Portion of the Right Membranous Labyrinth of the Rhea, Rhea americuna. x 12. 
The 
Taken by transmitted light and viewed from in front and slightly below. The 
eristee acustice in the ampulle are “simple.” The otolith of the utricle, o., is seen 
as a sharply defined black mass internal to and behind the ampulle of the superior 
and horizontal canals, and is very similar to the same structure as found in the emu. 
In the cochlea the tegmentum vasculosum, ¢.v., is shown and it will be noticed that 
the parallel venous channels are closer together and more numerous than in the emu. 
The columella has been removed from the oval window and the latter is more 
elliptical in shape than is the case in the emu. The large perilymph recess, 7.p., is 
not so definitely oval as in the emu, but is very similar to the perilymph recess in 
the monitor. The round window, f”., is large, occupying the whole of the floor of 
the perilymph recess : it is elliptical in outline and the membrane which closes it is 
richly pigmented. The walls of the perilymph recess are also pigmented. A saddle- 
shaped otolith is seen in the lagena, /, The little nipple-shaped termination to the 
cochlea has been broken off. 
PLATE 20, Fic, 7. 
Right Membranous Labyrinth of the Penguin, Spheniscus demersus. x 5. The 
organ is viewed from the inner aspect and. is rotated a little counter-clockwise. 
Numerous small air-bubbles are present in the vestibule and a portion of the canals. 
The cristz acustice in the ampulle are “simple.” It will be noticed that the lagenar 
portion, /., is relatively large. The perilymph recess is seen to the right of the 
cochlea, ¢c., and there is an oval opening, d.p., on the upper posterior surface of the cavity. 
This. opening corresponds with that found in the same position in the monitor and 
has not been found in any other bird hitherto examined. It is, however, represented 
in other birds by a short tube, the aqueduct of the perilymph, as described in the 
text. 
S., Superior canal. f., horizontal canal. 
p-, posterior canal. c.f, cartilaginous framework of cochlea. 
VOL. LXXX.—B. Pu 
