THE AUKS 



2305 



times deposited so far in that it is no easy matter to get at them; at other times 

 they lay their eggs on the broader shelves along -with the guillemots, but not so 

 closely together." 



Closely allied, both as regards structure, the color, and seasonal 

 change of their plumage, and habits, to the razorbills, the guillemots 

 differ by their more slender and straighter beak, in which there are no oblique trans- 

 verse grooves, while the upper mandible is slightly curved near the point, and has 

 a small notch on the side. The basal nostrils are partially closed by a membrane, 



Guillemots 



COMMON GUILLEMOTS. 



(One-fourth natural size.) 



which is itself partly feathered. There is still some degree of uncertainty as to the 

 number of species of the typical guillemots, some writers, like Mr. Seebohm, 

 recognizing but one, while others, like Dr. Sharpe, admit several. Whether, how- 

 ever, we regard them as species or varieties, all the forms are characterized by the 

 white plumage of the under parts; this white area in the summer dress stopping 

 short at the base of the throat, but in winter extending upward, as in the razorbill, 

 to the throat, chin, and sides of the head. In the typical form of the common 

 guillemot ( Uria troile) which inhabits both sides of the North Atlantic, the beak is 

 I4S 



