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flattened horizontally and supported by the anterior process of the os hyoides, which ad a ridge along
the middle of its inferior surface. At about four inches from the extremity of the horny damina the margins
become obliquely notched, and these notches, becoming deeper and closer together ute the extremity,
occasion the bristled appearance on each side of the tongue. These bristles, Mr. Vigors observes, were
generally applied to the morsels of food whilst held between the mandibles previously to ye ag swallowed.

The cornua of the os hyoides are 14 inch in length. The ¢rachea is narrow, and simple in its SPICE Eis the
rings somewhat flattened and decreasing in diameter towards the inferior extremity, from ves a single pair
of muscles pass off to the sternum. The length of the lower fourth of the tube, and the state of tension in the
bronchia, are regulated by a pair of small muscles, which, arising from the sides of the tracheal cartilages, a
snserted into the bone of divarication at the extremity of the trachea: and that this part of the tube is
subjected to variations in length is indicated by the tortuous character of the recurrent nerves attached to the
sides of the ¢rachea at this part. The lungs are small in proportion to the size of the bird, but of the usual
form and structure. The abdominal air-cells are of small size. The heart is of a more oblong form than
in general ; its apea, as it were, truncate; its length 1 inch.

The pectoral muscles, as in the Pstttacide, are but feebly developed, and the keel of the sternum is of
moderate size, not projecting more than half an inch from the plane of the bone. The sternum has four
notches at its posterior margin. The clavicles, or lateral halves of the fwrcu/a, are here, as in the Psittacide
and Struthionide, separate ; they are 1 inch in length, slender, pointed at their lower ends, and joined to each
other and to the sternum by ligament only.

The peculiar motions of the tail called for a particular examination of that part. It is difficult to state
the precise number of the caudal vertebre in consequence of the terminal ones being anchylosed, requiring
for this purpose the examination of a young specimen at a period before the anchylosis takes place. In the
skeleton of a Black-billed Toucan which I have examined, it would appear that three vertebre are thus
anchylosed, making the entire number of coccygeal vertebre nine. The Woodpecker has also nine caudal
vertebra, and this seems to be the greatest number found in birds. The first six of these vertebre in the
Toucan are articulated by ball-and-socket joints, the ball and the socket being most distinct in the last two
joints. That between the sixth and the anchylosed ver¢ebre is provided with a capsule and synovial fluid ; the
others have a yielding ligamentous mode of connexion. The spinous processes of these vertebre, both
superior and inferior, are of moderate size, but smallest in the sixth, where the greatest degree of motion
takes place. The transverse processes, on the contrary, are large and broad, so as almost wholly to prevent
lateral motion. The first of the anchylosed vertedre is broad and flat and of a rounded form, supporting the
two coccygeal glands: the last of these processes is compressed laterally, and of the ordinary ploughshare
form. The caudal vertebre can be inflected dorsad till their superior spines are brought into contact with the
sacrum ; in the opposite direction they can scarcely be bent beyond a straight line: and it is to this structure
of the bones and joints that is to be attributed the capability in the Toucan of turning its tail upon its back
(as represented in the Zoological Journal, vol. ii. pl. xv.), the muscles presenting comparatively few
peculiarities, since the motion alluded to is remarkable rather for its extent than the vigour with which it is
performed.

The principal e/evators of the tail are the sacro-coccygei superiores (sacro-sus-caudiens of Vicq d’Azyr).
They arise from two longitudinal ridges on the inferior and convex part of the sacrwm, and are inserted into
the superior spines of the first six vertebre by detached tendons, terminating broadly in the anchylosed vertebre.
The principal antagonists of these muscles, sacro-coccyge: inferiores (sacro-sous-caudiens of Vicq d’Azyr), pass
over the first five ver¢edre and terminate in the sixth and anchylosed vertebre : their origins are wider apart
than in the preceding pair of muscles, coming off from the margins of the sacro-sciatic notches. In the
interval are situated small muscles passing from the transverse processes to the inferior spines of the first six
vertebre.

From the limited nature of the lateral motions of the tail the muscles appropriate to these movements
are feeble, especially in comparison with those which are observed in the birds that spread their tail-feathers

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