IN THE GUBF OF OMAN. 295 



bill from edge of feathers (very clearly defined in these birds), 

 straight to tip, 1*14, 1*16, from gape to tip, 1"7, 1/78; tarsus, 

 1-73, 1-78 ; mid toe and claw, 1-65, 167. 



Three adults, one entirely white below, except a grey band 

 across the breast and with a yellowish white nuchal collar 

 from Orkney, sexed a male ; two entirely fuliginous, one from Ice- 

 land collected by Mr. Procter, and one from Norway. These 

 measure (I give the dimensions in the order that I have men- 

 tioned the specimens): — Wings, 12'0, 12'6, 124; bill in front, 

 as before, 1-18, 119, M8, from gape, 1-8, 1-82, 179 ; 

 tarsi, 1-77, 1'74, 1-7; mid toe and claw, 1-58, 1*65, 1-67. 



My bird is a male, immature, as it still has the striated crown 

 and nape, but not very young (probably about 20 months old), 

 as the chin, throat, and abdomen are white (a few stria only on 

 the two first), the barring is confined to breast and flanks, the 

 pale tippings have mostly disappeared from the upper plumage, 

 and the legs, feet, were entirely black. Well, the corresponding 

 dimensions of my bird are : — Wing, 12-85 (it was 13 full in the 

 fresh bird, but as I am comparing with skins, I take the present 

 existing dimensions) ; bill at front (as before from edge of 

 feathers), T33, from gape, 1*94 (it was 2'02 in the fresh bird) ; 

 tarsus, 181 ; mid toe and claw, 1*8. 



Let us contrast the dimensions. : — 



Mid Toe 

 Wings. B. at ft. B. fr, g. Tarsi. and Claw. 



specimens of 



Ric k a r d son's 



Skua, 3 adults, 



1 certainly male. 



specimen asia- ~\ 



120— 126 1-14— 1-19 17— 182 17— 178 158— 1-67 



ticus, immature £ 1285 133 194, 181 1-8 



male. ) 



Prima facie, therefore, ours is a somewhat larger bird, with an 

 appreciable longer bill and longer foot. 



Then the bill is very decidedly broader in asiaticus for the 

 basal half than in any of my specimens of Richardson's Skua ,• 

 the corneous portion is larger, the upper mandible is more de- 

 pressed at the base, and with the lower mandible is shallower than 

 my specimens of this latter bird. Again, the lower mandible is 

 less feathered. In all my specimens of Richardson's Skua, the 

 feathers terminate in a well-defined point exactly one inch from 

 the point of the lower mandible. In asiaticus, this point is 1*15 

 from the point. I am well aware that in such a case five speci- 

 mens is a very narrow basis from which to argue ; I merely note 

 these points for what they may hereafter prove worth. 



Then I observe that, as pointed out by Mr. Saunders, in all 

 my five Richardson's Skuas, the shafts of all the earlier prima- 

 ries are white alike in old and young, only brownish towards 



