ALCIDiE. 
293 
tliem to swim under the water. The body is clothed with 
a particularly compact plumage ; the legs are placed very 
far behind^ — a position which aids the birds much in swim- 
mings but renders them particularly bad walkers. These legs 
are flattened so as to present a sharpish edge before and 
behind^ which gives them the action of an oar. The family 
is a limited one in species^ but they are widely distributed. 
The Loons^ or Divers (Colymliis), are longer winged than 
the others, and have the feet webbed as in the dacks ; their 
tail is short, and when standing they rest upon it and the 
feet. The species are exclusively marine, and destroy great 
quantities of fish ; they lay two or three large spotted eggs. 
In the Grebes [Podiceps) the toes are separated nearly to 
the base and they are margined with a wide membrane; 
they have no vestige of a tail ; unlike the loons, they fre- 
quent fresh-water lakes, and form their nests among the 
reeds, raising them on a superstructure above water-mark ; 
they lay several eggs. The birds of the tribe Heliorninm 
have the feet lobed as in the grebes, but the tail is con- 
siderably developed, and the claws are sharper. 
The family Alcid^ is distinguished from the last family 
by the birds composing it being destitute of a hind toe; 
in some of the genera the beak is much compressed, in 
