190 



AUK GROUP 



distinct from the closed type, the sHt-likc apertures of the nostrils in 

 the skull, and the forked shape assumed by the fcather-bcarin<j tract on 

 the lower part of the back. In their peculiar bodily shape and up- 

 right position when standing, due to the backward situation of the 

 legs, and the deep and highly compressed beak, as well as by their 

 extremely close and compact plumage, auks present, however, a 

 marked contrast to the gulls and terns ; from which they also differ 

 very decidedly in their habits, more especially the great development 

 of the power of diving. Indeed, it is for the purpose of diving that 



MObNT&D ih THE ROWLAHLf AARO STuC;iOS 



KAZoKitii.i.s IN ni<i;i;i>i.N(;-i'i.LM.\(;i-: 



these birds arc so specially modified and differ so remarkably from 

 the normal type. Auks are also characterised by the fact that they 

 deposit their eggs, which are pear-like in form, on a bare ledge of 

 rock, in a cranny, or in a hole burrowed by the bird itself, without the 

 slightest attempt at a nest ; and that, as a rule, only a single egg, and 

 this of relatively large size, is laid by each female, while never more 

 than two eggs are incubated together. All the members of the group 

 are sea-birds, and are confined to the northern hemisphere, where they 

 breed in the sub-Arctic and Arctic zones, and in winter visit more 

 southern latitudes, although never reaching any part of the Intlian 

 region or crossing the equator. Two moults in the year are character- 

 istic of the group ; and it is a remarkable fact that among the puffin.s, 



