BIEDS OF NORTH AND MIDDLE AMEEICA. 701 



of femur; first digit of manus absent; tarso-metatarsus not laterally 

 compressed; tensor patagii and biceps slip peculiar (distinctive); 

 expansor socundariorum absent; thigh-muscle formula without Y, 

 sometimes (usually ?) without B (ABX — AX — , or AX + ) , the ambiens 

 always absent; only 1 brevis tendon; caeca absent or small (mere nip- 

 ples) ; intestinal convolutions of numerous (not less than six) loops; gall 

 bladder present; crop absent; tongue generally fleshy, elongated, tri- 

 angular, spiny only at base; anterior toes always fully webbed, the 

 third (middle) one longest; hallux always absent; young ptilopsedic, 

 tardily nidifugous (nearly nidicolous). 



Oil gland tufted, its apertures 2-S; aftershaft present; secondaries 

 aquincubital; dorsal pteryla without break between anterior and pos- 

 terior parts; ventral pteryla dividing much posterior to neck; rec- 

 trices, 12-18. 



The Alcse differ from the remaining Charadriiformes in possession 

 of all the above characters, and therefore seems to be more distinct 

 as a group from the Lari and Limicolae than these are from one 

 another. 



By some systematists (notably Sclater, Stejneger, and Beddard) the 

 Alcse are placed in the same suborder with the Loons (Gaviidae) or 

 one including both the Loons and the Grebes (Coljrmbidse). Un- 

 doubtedly the Auks and Loons are closely related; but the evidence 

 seems to point to a closer relationship of the former to the Gulls than 

 to the Loons, The latter differ in their holorhinal (instead of schizo- 

 rhinal) nostrils which, externally, are operculato; well-developed 

 (long) instead of absent or rudimentary (nipple-like) caeca; presence 

 of a powerful cnemial crest to the tibia, and possession of an ambiens 

 muscle and a well-developed hallux. In the Alcae the rectrices are 12 

 to 18 in number, while in the Gavidse they number 18-20. There are 

 also other diffe-rences, which it is unnecessary to mention here. 



Family ALCID^. 



THE AUKS. 



=Brachypteri Vieillot, Analyse, 1816, 66. 



=Alcadx Vigors, Trans. Linn. Soc. Lond., xiv, 1825, 498. 



<=Aldd3e Baird, Rep. Pacific R. R. Surv., ix, 1858, 755, 819, 900. — Lilljeborq, 

 Proc. Zool. Soc. Lond., 1866, 15.— Coues, Key N. Am. Birds, 1872, 338; 2d 

 ed., 1884, 797.— Carus, Handb. Zool., 1, 1868, 366.— Baird, Brewer, and 

 RiDQWAY, Water Birds N. Am., ii, 1884, 420, 461. — Stejneger, Standard 

 Nat. Hist., iv, 1885, 69. — American Ornithologists' Union, Check List,1886, 

 76; 3rd ed., 1910, 25.— Furbringer, Unters. Morph. Syst. Vog., ii, 1888, 

 1148.— Sharpe, Review Rec. Att. Classif. Birds, 1891, 72; Hand-list, i, 1899, 

 xiv, 130. — Gadow, Classif. Vertebr., 1898, 35.— Salvin and Godman, Biol. 

 Centr.-Am., Aves., iii, 1904, 446.— Knowlton, Birds of the World, 1909, 49, 

 396. 



The Alcidae are aquatic (swimming and diving) sea-birds with the 

 legs attached near the rear end of the body (pygopodous) , the anterior 



