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XIII. On the Anatomy of the concave Hornbill, Buceros cavatus, Lath. By Ricuarp 
Owen, Esq., F.Z.8., Assistant Conservator of the Museum of the Royal College of 
Surgeons in London. 
Communicated August 27, 1833. 
THE bird on which the following observations were made had been exhibited at the 
Society’s Gardens for about eight weeks, and died on the 15th of August last. It had 
attained nearly its full size, but had neither the plumage nor the configuration of the 
bill which characterize the adult ; the large quill-feathers of the wing and tail were in 
progress of development, while the warm and downy covering which defends the young 
bird had been in great measure lost by moulting: its death may therefore be attributed 
to the exhaustion consequent on the unfavourable circumstances, as to climate and 
captivity, in which it was placed, while undergoing a process so extensive and im- 
portant in its economy as the acquisition of the adult plumage. 
It measured from the end of the bill to the vent 2 feet 2 inches; the length of the 
bill was 7 inches. 
On the mandibles being separated the tongue is seen at the back part of the mouth ; 
its tip being 6 inches distant from the extremity of the jaws. It is of a triangular 
form, with the posterior angles produced backwards on either side of the laryngeal 
aperture ; measuring in length 1 inch, and in breadth at the base 8 lines. Its apex 
and surface are smooth. In texture, in configuration and in size, it consequently 
differs considerably from that of the Toucan, in which bird the tongue can be pro- 
truded from the mouth, and from its peculiar structure is evidently adapted for more 
extensive and varied actions than in the Hornbill. 
The air-cells are remarkably developed in the Hornbill. They may be observed ex- 
tending along the under side to the extreme point of the bones of the wings. The en- 
tire neck is occupied by a large cell, in which the esophagus and trachea are contained. 
The air-tube is connected throughout its whole length with the esophagus by a dupli- 
cature of the membrane of the air-cell, resembling a mesentery. This duplicature 
varies in breadth from 1 to 2 inches, allowing a free motion of the trachea from side to 
side. The nervi vagi, the cervical arteries and veins, and the esophagus, are as clearly 
exposed by the simple opening of this air-cell, as if they had been displayed by an ela- 
borate dissection. At the upper part of the neck the cervical air-cell communicates 
with others, partly surrounding the joint of the lower jaw and continued into the in- 
terior of that bone, and extending also to the back of the occiput to communicate 
with the cranium and cellular structure of the superior mandible. 
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