THE DIVING BIRDS 2301 



remarks, when seen from a distance, either on the wing, or diving and swimming, 

 it would undoubtedly be mistaken for one of these birds. Nevertheless, both in 

 structure and plumage, it is essentially a petrel; and we must accordingly regard 

 its auk-li'ke appearance and habits as special modifications for a peculiar mode of 

 life. These birds, according to Moseley, may be seen in calm weather in Royal 

 Sound floating in immense numbers on the ,water, the flocks sometimes extending 

 over acres, and causing the sea to appear literally black. They dive with extreme 

 rapidity, and when disturbed, rise and flutter a short distance along the surface, 

 after which they again drop and dive. 



THE DIVING BIRDS 

 Order PYGOPODES 



This group admits of much less concise definition than the preceding, unless 

 indeed we follow the example of many modern ornithologists in removing from it 

 the auks. It has been proposed to transfer the latter to the gulls, with which they 

 agree in having cup and ball articulations to the vertebrae of the back; but since it 

 is certain that all the primitive birds had cup-like articular surfaces to their verte- 

 brae, there seems no reason why the cup and ball 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 characterized 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 kneecap or patella to form a long spike projecting 

 upward 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 inva- 

 riably 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 

 confirmation 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 Limicolce or any of the remaining 

 orders; from all of which, except certain of the group named, they are distinguished 



