30 
CENTRAL HALL. 
tions, covered during growth with soft vascular hairy skin, and 
shed and renewed annually. 
On the wall at the back of the bay is placed a series of 
antlers of the Common Stag or Eed Deer [Cervus elaphus), grown 
and shed in six successive years, showing the changes which 
took place in their size and form, and the development of the 
branches or tynes in each year. 
The other systems of organs of the class will occupy the 
remainder of tliis bay. 
Bay III. Bay ISTo. III. is devoted to the class of Birds. An Albatross 
Sructure (Diomedea exulans) mounted with the wings expanded, shows 
of Birds. the most important characters by which a bird is externally 
distinguished from other animals. The surface of the body is 
clothed with feathers, which (in the majority of birds), by their 
great size and special arrangement upon the fore-limbs, enable 
these to act as organs of flight. The mouth is in the form of 
a horny beak. An Emu and Apteryx show the exceptional 
condition, found only in a comparatively few members of 
the class, of birds with wings so small as to be concealed 
beneath the general feathery covering of the body, and quite 
functionless. In the Penguin, the wings are reduced to the 
condition of fins, and are only serviceable for progression 
through the water. 
In the first wall-case the principal facts in the osteology of the 
class are shown. Sections of bones exhibit the large air cavities 
within ; a complete skeleton of an Eagle, with the bones sepa- 
rated and named, and mounted skeletons of the Ostrich, Penguin, 
Pelican, Vulture, Eowl, &c., show the chief modifications of the 
skeleton. The Apteryx shows the smallest, and the Erigate 
bird the largest bones of the wing, the correspondence of which 
can be readily traced by means of the labels attached to them. 
The under surfaces of the skulls of various birds are shown 
with the different bones coloured to indicate their limits and 
relations, followed by a series of the different types of sternum 
or breast-bone. 
The table-case in the middle of the bay contains illustrations 
of the external characters, the beak, the feathers and the tail, as 
well as of the fore and hind limbs, or wings and feet. By the 
aid of the explanatory labels, the essential characters and the 
