directed outwards. The second is nearly vertically placed, with its convexity directed backwards: it
terminates in a narrow point below. The third or superior spongy bone makes a small projection towards
the mesial plane, about the size of a pea. These spongy bones are formed by inward projections of the inner
and posterior osseous parietes of the nasal passage ; they are cellular, and air is continued into them from the
cranial diploé ; but the parietes of the nasal passage are entire and smooth, and lined by a delicate pituitary
membrane. — The inner table of the skull is continuous with the parietes of the nasal cavity, by means of the
bony canal which accompanies and protects the olfactory nerves, and which represents, as it were, a single
foramen of the cribriform plate of the mammalia. The communication of the cavity of the cranium with
that of the nose is thus similarly formed, and is only obstructed in the recent state by the pituitary membrane,
on the posterior cul de sac of which the olfactory nerve distributes its branches in a radiated manner. These
branches were confined, as Scarpa has observed in other birds, to the pituitary membrane covering the
septum narium and the superior spongy bone.

The external orifice of the meatus auditorius is situated about half an inch behind the lower boundary of the
orbit. The membrana tympani closes it so obliquely that its plane is directed almost backwards ; its anterior
edge is consequently about three lines from the external orifice, while its posterior margin is at least six
lines from the same point. It is convex outwardly as in birds generally. The apparatus of the internal ear
is easily exposed, the semicircular canals being lodged in a delicate reticulation of the diploé of the cranium.
These parts, with the ossiculum of communication and the cochlea, do not present any deviations from the
ordinary structure worthy of notice.—R. O.

DESCRIPTION OF THE PLATE.

Fig. 1. Section of the cranium and upper mandible of the | oo. Cornua of the os hyoides (cerato-hyal bones of Geof-
Ramphastos Toco. | froy).
a. The cancellated structure of the beak. | p. The trachea, or windpipe.
b. The cavity at the base. | q. The gullet.
c. Branches of the fifth pair of nerves. | Fig. 3. Vertical longitudinal section of the head.
dd. The external orifices of the nostrils. | The same letters indicate the same parts as in the pre-
e. The osseous parietes of the nasal passages. | vious figures. —
f. The osseous tubes protecting the olfactory nerves. | d. Shows the internal aperture of the nostrils.
g. The pituitary membrane exposed, and branches of the | r. The beginning of the spinal chord.
olfactory nerve radiating upon it. I s. The articulating surface of the occipital bone.
h. The superior semicircular canals of the internal ear. t. The nasal septum or partition.
21. Hemispheres of the cerebrum. u. The air-cell anterior to the orbit from which the air
k. Cerebellum. | passes into the mandible.
Fig. 2, The upper surface of the tongue. | v. The cancellated structure of the lower jaw.
1. The fringed or feathered portion of the tongue. | Fig. 4. Side view of the foot of Ramphastos Toco.
m. The orifice of the larynx. || Fig. 5. Under surface of the same.

. The orifice of the pharynx. I