900 U. S p. R. R. EXP AND SURVEYS — ZOOLOGY GENERAL REPORT. 



Family ALCIDAE.' 



Ch. — Bill without lamellae along the edges ; usually shorter than the head, compressed, and pointed. Anterior toes connected 

 fully by a continuous membrane ; hind toe usually entirely wanting ; the outer as largo as the middle ; the claws higher than 

 broad. Legs inserted far back. Wings short, concave. 



The Alcidae are readily distinguished from the Cohjmhidae by the absence of hind toe, the 

 continuous webbing of the toes, the compressed claws, and other characters. The species are 

 all exclusively marine, usually arctic, only coming southward in winter. Owing to their 

 boreal residence they are little known, and several species doubtless yet remain to be discovered. 



The present article embraces descriptions of nearly all the known species, including several 

 scarcely known as inhabitants of North America. They may be arranged under the following 

 sub-families, after Keyserling and Blasius. 



Alcinae. — Bill compressed to the very tip ; in the middle several times higher than wide, 

 the ridge and keel sharp or acute. Both jaws in the typical forms, with transverse ridges and 

 furrows in the middle, the base of the upper generally with a well marked swelling. 



Urinae. — Bill moderately compressed only, with the ridge and keel obtuse and rounded, and 

 without transverse ridges and grooves, or basal swelling. 



It may be proper to state that the arrangement adopted for the Alcidae is essentially that of 

 Bonaparte's Conspectus Gaviarum in Comptes Kendus, XLII, 1856. 



Sub-Family ALCINAE. 



The preceding diagnosis will express the characters of the sub-family sufficiently for our 

 present purpose ; it is composed of two sections : one, Alceae, including- Alca, with its sub- 

 divisions ; the other, Phalerideae, embracing Mormon, Phaleris, and the other curious forms 

 from the Arctic seas, with crests of curved feathers on the head. 



ALCA, Linn. 



.Ilea, Linnaeus, Syst. Nat. 1758. 

 Ch.— General form short, broad, and strong; wings short ; tail short. Bill about as long as the head, feathered at base, 

 much flattened laterally, wider, and somewhat hooked at the end ; upper mandible with oblique transverse grooves. Wings 

 short and feeble ; tail short, pointed ; legs and feet short and strong ; toes fully webbed. 



Chenalopex, Moehring.*^ 

 ALCA IMPENNIS, Linnaeus. 



TJie Great Auk. 



.9/cfl impennis, Linn. Syst. Nat. I, 176fi, 210.— Bon. Syn. 1828, 432. Note.— Aub. Cm. Biog. IV, 1838, 316.— 

 Figures.— BtFFnx, Pi. Knl 3(i7.— Kdwards, Birds, III, pi. 147.— Gould, B. of Eur. VII, pi. 400.— Aud. B. of Am. pi. 341 -, 

 Oct. ed. VII, pi 465. — Naumann, B. of Germ. pi. Xil. 



Sp. Ch.— Size large, general form stout ; head largo ; bill rather long, enrvcd, flattened laterally ; upper mandible composed 

 of two parts, the first of which is narrow, smooth, the terminal part with about »i.\ to eight or ten curved transverse grooves ; 

 under mandible with about ten nearly straight transverse grooves ; both mandibles densely covered at base with short velvet-like 

 feathers. The lateral feathers of upper jaw falling far short of the middle of the conimissure and of the end of the feathers of 

 lower jaw. Wings rudimenlal, not admitting of flight ; tail short ; legs and feet short, very robust. 



'Prepared by ,Mr. John ('assin of Philadelphia. 



'Wings rudiniental, adupted to swiminiii;; only, and not to flight, not reaching to the rump. 



