52 



THE AUKS 



the surface in winter. With these plates disappears the horny, 

 whitish, curiously indented fillet along the base of the upper mandible 

 (Fig. 1, F), while at the same time the yellow rosette (Fig. 1, Y) at 



Fig. 1. PUFFIN IN SUMMER. 



the gape becomes shrivelled and discoloured, and the appendages 

 above and below the eye disappear. The front half of the beak, con- 

 sisting of the red triangular end, the red ridges and three furrows, 



Fig. 2. PUFFIN IN WINTER. 



remains unaltered (Figs. 1, 2, R). On examining skins of razorbills 

 at the Natural History Museum, South Kensington, I found that this 

 species also showed in winter a distinct diminution in the size of 

 the posterior half of the bill, the part, that is, behind the median 



