SYSTEMATIC SYNOPSIS.— PYGOPOBES. 



separately, after the breed- 

 ing season, to be renewed 

 again from the soft basement membrane. 

 Tlie absence, in icinter, of the horny plate 

 at the angle of the mouth of Simorhijnclms 

 cristatellus, had been noted (Key, p. 342), as 

 well as the presence or absence of the horn of 

 Ceratorhina ; but we had no knowledge of the 

 process by which the change was eifected, prior 

 to Bureau's studies. In the Puffins there is also 

 a moult of the excrescences upon the eyelids, 

 and a shrivelling of the colored rosette at the 

 comer of the mouth. 



The Auks are confined to the Northern 

 Hemisphere. Some representatives have been 

 found as far north as explorers have penetrated. 

 The great majority live in more temperate lati- 

 tudes. A more or less complete migration takes 

 place with most species, which stray southward, 

 sometimes to a considerable distance, in the au- 

 tumn, and retuni north again to breed in the 

 spring. A few species appear nearly stationary. 

 The most southern recorded habitat of any 

 member of the family is about latitude 21° N., 

 on the Pacific coast of North America, but this 

 is rather exceptional. The species are very 

 unequally divided between the two oceans. The 

 Atlantic has but few representatives compared 

 with the Pacific. On the northern coasts of 

 the latter the family reaches its highest devel- 

 opment ; the greatest number of species, of th 

 most diversified forms, are found there, though 

 the number of individuals of any species does 

 not surpass that of several Atlantic species. 

 Comparatively few species are common to both 

 oceans. All the members of the family are ex- 

 clusively marine. They are decidedly grega- 

 rious, particularly in the breeding season, when 

 some species congregate in countless numbers. 

 Usually one, often two, rarely three eggs are 

 laid, either upon the bare rock or ground, or in crevices between or under rocks, or in burrows 



Fig. 631. — EgKing in Alaska on cliffs iuliabited by 

 Kittiwaket" (p. 748), Auks, etc. (DesigneJ by H. W. 

 Elliott. From Harper Brothers.) 



