212 
ALCADA2, OR AUKS. 
bill black, white at the tip; the lore greyish or 
pinkish white; feet and legs blackish-green, paler 
on the insides. The plumage of one shot in the 
river Annan, in winter, is pale umber-brown, darker 
on the wings ; on the cheeks and sides of the neck 
there is a tint of rufous, and the chin and under 
parts are of a clear and silvery white. 
ALCADiE, OR AUKS. 
The birds contained in this group are entirely mari- 
time in habit. In the preceding family we saw the 
legs placed very far behind and the feet very ample ; 
in the Auks we have the former structure continued, 
with the tarsi short and the feet small, and these 
members are not so amply developed or adapted for 
so swift a passage through the water, nevertheless 
the Auks are expert divers, and procure their food 
by that means alone. They do not breed on the 
ground, but either burrow or select precipitous rocks 
for this purpose ; and they sit and move with ease 
on the shelves and ledges, keeping themselves nearly 
in an upright posture, and resting on the whole 
posterior edge of the tarsus. The wings arc short, 
but in many are capable of a swift and rapid flight ; 
while in a few these organs are totally unable to 
raise the bird from the water, and act only as power- 
