50 COLYMBIFORMES chap. 



brane, but whereas Divers have the anterior toes fully webbed, 

 their allies have them surrounded by large lobes of skin, con- 

 nected only at the base. The claws are abnormally broad and 

 flat in Grebes, the outer margin of the third being serrated. 

 In the Colyml)idae the wing is short, narrow, and pointed, with 

 eleven primaries and about twenty secondaries ; in the I'odici- 

 pedidae it is still shorter and concave in form, with twelve 

 primaries Vnit rarely twenty secondaries ; in the latter no true 

 rectrices can be distinguished, though a tuft of downy feathers 

 exists, while in the former they are normal though much reduced, 

 and number from eighteen to twenty. Grebes have bare lores, 

 and are frequently adorned in the breeding season with crests or 

 tippets of a golden or brownish colour ; the dense glossy plumage 

 being more commonly used for decorative purposes than the duller 

 coats of Divers. The tongue is always long and pointed, the 

 syrinx is tracheo-bronchial, the nostrils are pervious, an aftershaft 

 is present, and both adults and young are uniformly downy. 

 Fossil remains from the Oligocene of France and southern England, 

 indicating a genus intermediate between the two Families, have 

 been named Colyniboides} 



Fam. I. Colymbidae. Colymhus septentrionalis, the Eed- 

 throated Diver of the Arctic and sub-Arctic parts of both worlds, 

 is brownish black in summer, with white under-parts and white 

 specks above ; the head and neck are lead-coloured, except the 

 nape, which is black with white streaks, and the mid -throat, 

 which is reddish-chestnut. C. arcticus, the Black-throated Diver, 

 found in the same regions though with a different distribution, 

 as for instance in Scotland, is blacker, with white bars as well as 

 spots ; the crown and hind neck being ashy grey, the sides of the 

 latter striped with black and white, and the throat pm-plish-black, 

 interrupted by a semi-collar of white with vertical black lines. 

 C. 2)cicificus of western North America is barely separable. C. 

 glacialis, the Great Northern Diver, has a much more restricted 

 range, breeding in Iceland, Greenland, and the Fur Countries as 

 far west as the Great Slave Lake, where it meets C. adamsi 

 (hardly differing except in the yellowish-white bill), which 

 extends thence to Northern Asia, and possibly to Spitsbergen 

 and Jan Mayen. The former is black above, with belts of white 

 spots making a " chess-board " pattern ; the lower surface is 

 1 Lydekker, Cat. Fussil Birds Brit. Mus. 1891, p. 192. 



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