192 ON THE CLASSIFICATION OP BIRDS. 
although much more common on the arctic circle. 
The second (Uria) includes the guillemots, distin- 
guished from the last by the absence of the hinder 
toe ; and these again are confined to the Northern 
Ocean. The third and fourth are Podiceps and Podia, 
both of which agree in having the membrane between 
the toes divided into lobes, similar to those on the feet 
of the coot ; but in the first the hinder toe is lobated, 
wliile in the latter it is simple. The grebes are the 
most imperfect flyers, since the divers have their 
wings not much shorter than several of the ducks. 
(214.) The Alcid* form the third principal fa. 
mily, and include the penguins, the puffins, and all 
those singularly constructed groups where the wings 
are abortive, or, in other words, assume more the 
appearance, as they perform the office, of fins: the 
feet, moreover, are so little adapted for walking, diat 
even the obsolete toe, .seen in the ducks and divers, is 
here generally wanting. We thus see the power of 
swimming developed in the most perfect manner in 
birds which, in every other faculty, are the most imper- 
fect in creation. The natural series of the genera, by 
some, have been commenced with Uria/ by others, 
with some of the Aicw, or puffins. The little auk 
(Mergulug) has been detached on account of its short, 
thick, and convex bill, the base of which is covered 
with the frontal feathers : there is but one species, a 
polar bird, yet sometimes seen on the British coasts : 
this form may probably be represented in the southern 
hemisphere by the crested auks {^Phaleris Tern.) — the 
species of which are but obscurely understood : the 
arctic puffin, and two other northern species, form the 
restricted genus Mormon. The great auk and the 
razorbill are now almost the only species left in the 
original genus Alca of Linna;us : the first is nearly the 
size of a goose, and is occasionally found in the arctic 
seas : this singular and very rare bird is totally without 
the power of flight ; and the latter species can only 
raise itself on wing just above tlie surface of the sea. 
