$00 U. 8 P. RB. R. EXP. AND SURVEYS—ZOOLOGY—GENERAL REPORT. 
Family ALCIDAE, 
Cu.—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 Jarge as the middle ; the claws higher than 
broad. Legs inserted far back. Wings short, concave. 
The Alcidae are readily distinguished from the Colymbidae 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. 
AtctnaAE.—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. 
Urinau.—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 Rendus, 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 s 
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, 
Alca, Linnarvs, Syst. Nat. 1758, 
Cu.— General form short, broad, and strong ; wings short; tail short. Bill about as long asthe 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. 
The Great Auk. 
Alca impennis, Linn. Syst. Nat. I, 1766, 210.—Bon. Syn. 1828, 432. Note.—Avp. Orn. Biog. IV, 1838, 316.— 
Ficures.—Burron, Pl. Enl 367.—Epwanrps, Birds, IU, pl. 147.—Gou pn, B. of Eur. VII, pl. 400.—Aup. B. of Am. pl. 341; 
Oct. ed. VII, pl 465.—Naumann, B. of Germ. pl. 337. 
Sp. Cu.—Size large, general form stout ; head large ; bill rather long, curved, flattened laterally ; upper mandible composed 
of two parts, the first of which is narrow, smooth, the terminal part with about six 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 commissure and of the end of the feathers of 
lower jaw. Wings rudimental, not admitting of flight ; tail short ; legs and feet short, very robust. 
‘Prepared by Mr. John Cassin of Philadelphia. 
*Wings rudimental, adapted to swimming only, and not to flight, not reaching to the rump. 
