870 SKULL 



size of a common Gull, Larus canus, and presenting, irrespective of sex, 

 two very distinct phases of plumage, one almost wholly sooty-brown, 

 the other particoloured — dark above and white on the breast, the 

 sides of the neck being of a glossy straw-colour, and the lower part 

 of the neck and the sides of the body barred with brown ; but a 

 singular feature in the adults of this species is that the two median 

 tail-feathers, which are elongated, have their shaft twisted towards 

 the tip, so that in flight the lower surfaces of their webs are pressed 

 together vertically, giving the bird the appearance of having a disk 

 attached to its tail. The second and third species so closely 

 resemble each other, except in size, that their distinctness was for 

 many years unperceived, and in consequence their nomenclature is 

 an almost bewildering puzzle. Mr. Saunders (torn. cii. p. 322) thinks 

 that the larger of them, which is about the size of a Black-headed 

 Gull, should stand as »S'. crepidatus, and the smaller as »S'. parasiticus, 

 though the latter name has been generally used for the larger when 

 that is not termed, as it often is, S. richardsoni — a name that 

 correctly applies only to whole-coloured examples, for this species 

 too is dimorphic. Even its proper English name ^ is disputable, 

 but it has been frequently called the Arctic Gull or Arctic Skua, 

 and it is b}^ far the commonest of the genus in Britain, and perhaps 

 throughout the northern hemisphere. It breeds abundantly on 

 many of the Scottish Islands,^ and in most countries lying to the 

 northward. The nest is generally in long heather, and contains 

 two eggs of a dark olive colour, suffused Avith still darker brown 

 patches. Birds of either phase of plumage pair indiscriminately, 

 and the young shew by their earliest feathers whether they will 

 prove Avhole or particoloured ; but in the immature dress of the last 

 the upper surface is barred with pale reddish-brown. The smallest 

 species, commonly known in English as the Long-tailed or Buffon's 

 Skua, rarely exhibits the remarkable DIMORPHISM (p. 149) to which 

 the two preceding are subject, but one instance (Ibis, 1865, p. 217) 

 apparently being on record. It breeds abundantly in some seasons 

 on the fells of Lapland, its appearance depending chiefly on the 

 presence of Lemmings, on which it mainly preys. All these three 

 species occasionally visit the southern coasts of Europe in large 

 flocks, but their visitations are highly irregular. 



SKULL, the comprehensive word for all the bones of the head, 

 which may be conveniently gi'ouped as those forming the CRANIUM 



1 It is the Fasceddar or Fasgadair of the Hebrides, the Shooi of the Shet- 

 lands, and the Scouti-allen of the fishermen of Orkney and on the east coast 

 of Scotland. 



- Pennant was the first to discover that it bred in the British Islands, by 

 finding it on the 1st of July 1772 on .Jura, which, thanks to the protection 

 accorded to it, it still inhabits, and this must be the most southerly point in its 

 breeding-range. 



