74 
NATURAL HISTORY. [NEW BUILDING. 
The family of Ducks ( Anatidce , Cases 135—151) have 
short or moderate wings,, their bill covered with a soft skin, 
and furnished on the edge with a series of plates, through 
which they filter the water, and thus separate their food. 
The Swans and Geese have beautifully formed, long necks; 
the Cereopsis has the base of the beak covered by a yellow 
skin, and the Hydrobates the hind toe large, and webbed 
beneath. The Merganser (Mergus) has a slender, serrated 
bill; and the Flamingo ( Phcenicopterus ) combines the long 
legs of the Waders with the shining velvet plumage, com¬ 
pressed legs, and serrated bill of the Ducks. 
The family of the Divers (Colymbidee , Cases 152 and 
153) have very moderately feathered short wings, and the 
legs placed so far back on the body, that they can assume 
an erect position. The bill is compressed at the tip, and 
smooth. They live constantly on the water, and dive for 
their food. The Grebes have a very silky plumage, and 
the toes separate, and fringed on the side by a membrane. 
These birds live on lakes, and are said to carry their young 
under their wings when alarmed. The Finfoot ( Podca ) 
has the feet of the Grebes, but the tail is longer, and the 
claws sharp; the Divers ( Colymbits ) have completely- 
webbed-feet, and live on the sea-coast. 
The family of Auks ( Alcidce , Cases 154 and 155) have, 
like the Divers, very short wings, and the legs placed far 
behind the centre of the body, which enables them to stand 
nearly erect, but they have the toes all unitecbby a web. 
In some the wings are covered with feathers, and have no 
hind toe, as the Guillemots (Uriel), Penguins (Spkenis- 
cus), and Puffins (Fratercnla). Others have the wings 
covered with small scale-like feathers, and all the four toes 
directed forwards. 
The remainder of the web-footed Birds have very long 
wings, which enable them to suspend themselves in the air 
for a great length of time, so that it almost appears to be 
their proper sphere, as they are seldom seen on the ground 
except in the breeding season. 
The family of Gulls (. Laridcc , Cases 156—161) have 
the hind toe free, and sometimes very short and rudi¬ 
mentary, and a compressed bill. The Petrels have the 
bill stronglv hooked at the end ; their hind claw is placed 
immediately on the tarsus, without any toe. Of all the 
