418 NATATORES. ALCADAL, 
comprising the Guillemots (Genus Uria), Auks (Genus Al- 
ca), Penguins (Genus Aptenodytes), and other nearly allied 
groups, forms a second typical division of the Order Nata- 
tores. 'The greater part of the Alcade@ are distinguished by 
having only three palmated toes, and where a fourth or hind 
toe does exist, it is very small, and without a membrane ; 
and also directed forwards, as in Pe/ecanide, thus leading the 
way to the connexion of the present with that aberrant fa- 
mily. We also find in them the shortness of wing, and con- 
sequent deficiency in power of flight (which seems in general 
most prevalent as aquatic habits become most decided), car- 
ried to the greatest extreme ; the wings of the Penguins, and 
other nearly allied genera, being so short and imperfectly de- 
veloped, as to be totally unfit for the purpose of flight, and 
adapted to act merely as fins, in aiding their progress be- 
neath the water. As in the Colymbida, the legs of the birds 
of this family are placed far backwards, but at scarcely so 
great an angle with the body as in the former, in consequence 
of which they are enabled to sit in an upright attitude, rest- 
ing equally on the foot and the whole length of the tarsus. 
They are all attached to the ocean, never resorting to fresh 
water, like the Colymbi. Many of the species that are able 
to fly, nestle on rocks and precipices, where they lay a single 
ege, of a conical form, a shape which prevents it from rolling 
away or moving (except within a circle of the diameter of its 
own length), on the bare rock where it is deposited. Some 
burrow in the light sandy soils of the small islands they fre- 
quent ; and the Penguins, and other species, that have not 
the power of flight, incubate upon the shore immediately 
above high-water mark. The bill has a variety of form in 
the different genera, but commonly much compressed, and 
often grooved on its sides ; exhibiting through all its modi- 
fications a beautiful illustration of the progressive series of 
affinities that unite the members with each other. The food 
of this family consists of fish, crustaceae, and other marine 
animal productions. 
