IVORY WIIALE-GULL. 509 



loith yelloxo. Young ivith the bill dusky, ^Kile yellow at the 

 end ; feet black ; plumage lohite, variegated tcith broionish- 

 black, each feather having a large round spot toward the end ; 

 forehead and loral spaces bluish-grey. 



Male in Summer. — The " Ivory Gull," so named on 

 account of the peculiar white colour of its plumage, having 

 occurred in Britain only in a very few instances, and these in 

 the winter season, I am obliged to take its description in 

 summer plumage from a specimen in my collection, procured 

 in Davis' Straits. 



This bird is apparently of a rather robust form, with the 

 neck strong, and of moderate length, the head rather large, 

 ovato-oblong, anteriorly narrowed. The bill is short, robust, 

 compressed in a less degree than in most sjjecies of this family, 

 nearly straight ; the upper mandible with the dorsal line 

 nearly straight, being very slightly concave for half its length, 

 then moderately decurved, the ridge convex, the sides con- 

 siderably so, the edges sharp, and toward the end slightly 

 arched, the tip rather obtuse ; the lower mandible with the 

 angle rather long and narrow, the prominence small, the dor- 

 sal line ascending, and slightly concave, the sides nearly flat, 

 the edges sharp and someAvhat inflected, the tip narrow, but 

 obtuse. 



The nostiils, which are linear, bvit a little wider anteriorly, 

 are five and a half twelfths in length. The eyes rather small, 

 four-twelfths across. The feet are very short, but pretty 

 stout ; the tibia bare for only a quarter of an inch ; the tarsus 

 very short, moderately compressed, with about twenty scu- 

 tella, of which the upper are extremely narrow, the scales on 

 the hind part small and prominent. The hind toe is very 

 small, with a single scutellum besides scales ; the second or 

 inner toe short, with fourteen scutella, the upper very small ; 

 the third a little longer than the fourth, with twenty-eight ; 

 the fourth, much longer than the second, with about twenty 

 scutella. The soles are flattened and rough, the margin 

 thick and prominent, the membranes with a denticulate in- 

 curved margin, that of the outer sinuous, with a sinus and 

 prominence. The skin of the whole foot is remarkably thick 



