AUKS. 53t 
structure should not have been independently acquired in two distinct groups. 
Moreover, the auks differ from the gulls in the absence of any projecting process 
to the lower end of the humerus. 
In this wider sense the diving-birds are characterised externally by the 
extremely backward position of their short legs, in which the front toes are either 
completely webbed or lobed, the first toe being either absent or rudimentary. In 
the skull the palate is of the cleft (schizognathous) type, the lower jaw is abruptly 
truncated behind, and there are large grooves for the reception of glands on the 
forehead, which are separated from one another merely by a narrow ridge. 
The humerus has no process at its lower end; but the tibia has an upwardly 
projecting crest, which may unite with the knee-cap or patella to form a long 
spike projecting upwards in front of the femur. The young are born covered with 
down or feathers, and are soon active. In the plumage, the spinal feather-tract is 
either forked on the upper part of the back, or not defined on the neck; while the 
oil-gland is invariably tufted. The wings are relatively short; and the beak is 
comparatively straight and often much compressed, with its horny sheath generally 
composed of but a single piece. 
Contrasted with the other ordinal groups in which the palate is of the cleft 
type, the divers are readily distinguished from the tube-nosed birds by the normal 
conformation of their nostrils, their active young, and the absence of a projecting 
process to the lower end of the humerus; the latter feature, together with the 
more marked upward extension of the crest of the tibia, and the lack of any 
perforations in the bones of the second digit of the wing, differentiating them from 
the gulls. They are not likely to be confounded with the Limicolw or any of the 
remaining orders; from all of which, except certain of the group named, they are 
distinguished by the presence of grooves on the front of the skull. The group 
may be divided into three families, of which the second and third are much more 
closely related to one another than they are to the first. 
THE AUKS. 
Family ALCIDZ. 
The auks are characterised externally by the absence of the first toe; 
while in the skeleton the crest of the tibia is relatively short, the metatarsus is 
not laterally compressed, and the vertebre of the back are articulated together 
by cup-and-ball jomts. The front toes are fully webbed and furnished with © 
sharp, claw-like nails; the tail, although short, is normal, and the beak, 
although frequently much compressed, deep, and short, is subject to great 
variation in form. The family includes the true auks, guillemots, pigmy-auks, 
and puffins; all of which are marine, and confined to the colder regions of the 
Northern Hemisphere. 
The typical members of the family are characterised by the large 
size of the compressed beak, marked in front by oblique grooves, 
and feathered at its base close up to the slit-like nostrils, which are almost 
concealed by a dense velvety feathering, completely fillmg the fossee in which 
The True Auks. 
