flattened horizontally and supported by the anterior process of the os A//aides, which forms a ridge along 
the middle of its inferior surface. At about four inches from the extremity of the horny lamina the margins 
become obliquely notched, and these notches, becoming deeper and closer together towards 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 being swallowed. 
The cornua of the os hyoides are 1.1 inch in length. The trachea is narrow, and simple in its structure, the 
rings somewhat flattened and decreasing in diameter towards the inferior extremity, from which 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, are 
inserted 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 trachea 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 apex, as it were, truncate; its length 1 inch. 
The pectoral muscles, as in the Psittacidae, 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 furcula, are here, as in the Psittacidce 
and Struthionidce, 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 vertebrae 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 vertebrae are thus 
anchylosed, making the entire number of coccygeal vertebrae nine. The Woodpecker has also nine caudal 
vertebrae, and this seems to be the greatest number found in birds. The first six of these vertebrae 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 vertebrae is provided with a capsule and synovial fluid; the 
others have a yielding ligamentous mode of connexion. The spinous processes of these vertebrae, 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 vertebrae 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 vertebrae 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. pi. 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 elevators 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 sacrum, and are inserted into 
the superior spines of the first six vertebrae by detached tendons, terminating broadly in the anchylosed vertebrae. 
The principal antagonists of these muscles, sacro-coccygei inferiores ( sacro-sous-caudiens of Vicq d’Azyr), pass 
over the first five vertebrae and terminate in the sixth and anchylosed vertebrae : 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 
vertebrae. 
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 
