798 SYSTEMATIC SYNOPSIS. —PYGOPODES. 
— 
separately, after the breed- 
ing season, to be renewed 
again from the soft basement nembrane. 
The absence, in winter, of the horny plate 
at the angle of the mouth of Simorhynchus 
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 effected, prior 
to Bureaw’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 
corner 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. Amore or less complete migration takes 
place with most species, which stray southward, 
sometimes to a considerable distance, in the au- 
tumn, and return 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 the 
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- a 
rious, particularly in the breeding season, when _— Fig. 531, — Egging in Alaska on cliffs inhabited by 
some species congregate in countless numbers. .Kittiwakes (p. 748), Auks, etc. (Designed by H. W. 
Elliott. From Harper Brothers.) 
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 
