AUKS. 45 
Order X. ALCIFORMES. 
Family Aucrpe. AUKs. (Plates IV., V.) 
The Auks, Guillemots, Razor-bills and Puffins, included in this family, 
form a group of exceptional interest on account of the modifications of 
structure which they have undergone to adapt them to a purely pelagic 
life. Though allied to the Gulls and more distantly to the Plovers, they 
are now superficially very different, and as in the Grebes and Divers the 
shape and carriage of the body are specially suited to their peculiar 
habits. Their distribution is confined to the coasts of the North 
Circumpolar region, none being found either in the tropical zone or in 
the Southern Hemisphere. Black and white are the predominating 
colours in the plumage of these birds. They breed generally on rocky 
cliffs and islands in enormous colonies, make no nest, and the female lays 
her one or, in some species, two eggs on the bare rock or, as in the case of 
the Puffins, in a rabbit-burrow or hole tunnelled by the birds themselves. 
The young are covered with down when hatched, and in their first 
plumage differ but little from the adult. 
The smallest members of the group are the little Auks, represented 
on the top shelf of this case by several diminutive species. Least of 
these is the Minute Auk (Simorhynchus pusillus) (390), remarkable on 
account of its extremely small bill, while the Pigmy Auk (S. pygmaeus) 
(391) and the Crested Auk (S. cristatellus) (892) have an elongate frontal 
crest of narrow feathers curving forward over the bill. In these species, 
as in their allies the Puffins, the supplementary ornamental sIields on 
the bill are cast after the breeding-season, and the bill then appears much 
smaller and of a dull brown colour. The Perroquet-Auk (Phaleris 
psittaculus) (398) from the North Pacific is another curious little form, 
and the Unicorn Puffin (Cerorhyncha monocerata) (894), from the North 
Pacific and Bering Sea, has a peculiar horny excrescence at the base of 
the bill during the breeding-season. 
The Common Puffin or Sea-Parrot (Fratercula arctica) (897) [PI.IV.], 
a common British Species, the Horned Puffin (F. corniculata) (396), and 
their ally the Tufted Puffin (Lunda cirrhata) (395), differ from all the 
species already mentioned in having the claw on the inner toe very 
strongly curved. During the breeding-season these birds have the bill 
brilliantly ornamented, but m autumn a remarkable moult takes place, 
and the coloured shields fall off, leaving the bill about half its former 
size. This is clearly illustrated on the tablet exhibited in the Case, 
where the head of the Common Puffin is shown with the recently cast 
shields alongside the bill. 
From the coasts end islands of the North Pacific and Bering Sea 
[Case 24. ] 
