MR. R. OWEN ON THE ANATOMY OF THE CONCAVE HORNBILL. 119 
close together at the end of the fold between the insertions of the hepatic ducts. On 
referring to the table of the insertions of these ducts in Cuvier’s ‘ Anatomie Com- 
parée’', the arrangement in the Hornbill will be found to correspond with that in the 
Heron there given, and may be expressed thus: Ist p. — H.— 2nd and 3rd p. — C. H: 
The spleen is situated at the right side of the upper end of the gizzard. 
The trachea has a single pair of muscles. 
The heart and kidneys present the usual peculiarities of the class. 
The ureters emerge from the inner side of the lower end of the third lobe. Where 
they emerge, a large vein from the tail enters a deep groove, which continues along the 
inner sides of each lobe, receiving the renal veins by large orifices. A vein from the 
posterior extremity enters the third lobe on its outer aspect, and ramifies in the gland. 
This I conclude to be the vein from which, as Jacobson has shown, the urine is in part 
secreted. 
The supra-renal glands, of the usual bright yellow colour, are closely attached to the 
coats of the inferior vena cava. The testes are situated anterior to the above glands, 
and were of minute size, not exceeding that of a grain of rice. 
On laying open the cloaca anteriorly, the division into which the ureters open, or 
rudimentary bladder, is seen to be formed by two transverse semilunar folds about a 
line in breadth, and gradually lost on the anterior part of the rectum. The space 
between these ridges is little more than a line. The bursa Fabricii (which I regard as 
analogous to the anal glandular scent organs of the Mammalia,) opens into the back part 
of the outer vestibule. It is of a triangular form, two thirds of an inch in length, and 
is surrounded by a capsule of muscular fibres. The common vestibule is half an inch 
in length ; and closed as usual by a strong sphincter. 
The mechanism by which the movements of the immense mandibles of this singular 
bird are effected, was next examined. The os quadratum and the other bones forming 
the articulation of the jaws, are accurately described by Cuvier?. The digastricus, or 
its analogue, which in Birds has no middle tendon, arises from the whole occipital de- 
pression, and descends vertically to be inserted into the angle of the lower jaw, which 
projects posteriorly to the articulation. We occasionally find a similar simple dispo- 
sition in the Mammalia, even in the Orang Utan. 
The temporal muscle does not exceed half an inch in breadth ; it arises from the 
temporal fossa, passes within the zygoma, and is inserted into the slightly developed 
coronoid process immediately anterior to the articulation. The pterygoider externt and 
interni are proportionately more developed than the temporalis: they assist that muscle 
in closing the bill, whilst they draw the inferior mandible forwards, and perform the 
lateral motions: these and the muscles of the os quadratum have the usual attach- 
ments. A strong ligament occupies the place of the masseter; it passes from the 
sygoma to the outer side of the condyle of the lower jaw, immediately in front of the 
1 Tom. iv. p.55. * Anat. Comp., tom. iii. pp. 63, 64. 
