528 On Anatomical Structure and Relationships of the Labyrinth. 
The 
PuatEe 20, Fie. 8. 
Right Membranous Labyrinth of the Penguin, Spheiiscus demersus. x 5. The 
organ is viewed from the outer aspect, above and in front. As the arch of the 
horizontal canal passes under that of the posterior canal at « it comes into contact 
with the latter, but there-is no actual channel of communication between the two 
canals. 
c., cochlea. p. posterior canal. 
PLATE 20, Fic. 9. 
Portion of the Right Membranous Labyrinth of the Penguin, Spheniscus demersus. 
The 
x 10 ca. Viewed from behind and below. The lower part of the perilymph recess 
has been removed along with the round window (if present in this bird). The oval 
opening, 0.0., from the cochlea, c., into the perilymph recess is clearly seen, and is 
bounded along one border by the lower limb of the cartilaginous framework, c.f, 
in the cochlea. The bending of this cartilaginous framework is seen at the vestibular 
end of the cochlea. The tegmentum vasculosum, ¢.v., has been to a considerable 
extent destroyed, but a fragment may be seen at the vestibular end of the cochlea. 
l., lagena. 
PuatE 20, Fie. 10. 
Right Membranous Labyrinth of the Spiny Ant-eater, Echidna aculeata. X 6. 
Viewed from the outer aspect and below. The semicircular canals are well curved 
and similar to those of other mammals, while differing from those of the platypus 
(see text). The perilymph space is fairly well marked in the canals and can be 
traced easily round the whole circumference. The cone-shaped recessus utriculi, 7.u., 
is seen lying between the ampulla of the horizontal canal, 4., and the outer wall 
of the utricle ; and the nerves supplying the ampulle and recessus utriculi are also 
seen. The oval window, f.o., is almost circular in shape and looks directly into the 
saccule. Immediately to the left of the oval window the perilymph recess, 7p., 
may be seen opening out of the cochlea as an egg-shaped cavity, and the round 
window, f7., iS seen on its outer surface as an oval opening.. At its posterior 
extremity the perilymph recess again narrows down and tapers off into the aqueduct 
of the perilymph. The latter channel only occupies a portion of the irregular mass 
at the lower left-hand corner of the plate, a portion of the jugular vein, 7., being 
also present in the mass. In this mass, however, the aqueduct of the perilymph, p.c., 
is seen on the right side as a somewhat lighter band. The cochlea, ¢c., is well curved, 
and the lagena, /., may be seen as a kidney-shaped structure at the tip of the cochlea 
on the side nearest to the vestibule. The irregular slit at the tip of the cochlea is 
an artefact produced by the long immersion of the head in alcohol. The white 
deposits in the different parts of the organ are not to be looked upon as otoliths 
unless their presence in these situations is confirmed by further examinations (see 
text), 
s., Superior canal. h., horizontal canal. 
p., posterior canal. 2.8., nerve to ampulla of superior canal. 
