ALCID.E — THE AUKS. 461 



the Yukon Kiver, Sitka, Anderson Uiver, and Greenland. The ground-color varies 

 from a deep reddish umber, or a deep raw umber, to a grayish green. The markings 

 are usually small, sparse, and of a brownish black. The eggs vary in their length 

 from ^.05 to 3.00 inches, and in their breadth from 1.70 to 1.S5. 



Family ALCID/E. — The Auks. 



Char. Swimming birds with the feet situated far back, the anterior toes fully 

 webbed, and armed with strong claws, the hallux entirely absent. Lores feath- 

 ered ; tail normal, always short ; nostrils without overhanging membrane. Bill 

 excessively variable in form. 



The above diagnosis, though brief, is quite sufficient to distinguish this family 

 from that most nearly related — the Urinatoridce — which differs essentially in the 

 possession of a well-developed hind toe, and in the nostrils being overhung by a 

 membrane. The different genera exhibit remarkable extremes of form, especially 

 of the bill (the variation of other parts being comparatively trifling), and, to a less 

 extent, of size. 



All the genera, and most, if not all, of the species, are American, the family being 

 of circumpolar distribution, with few, if any, forms peculiar to either continent, the 

 chief difference being between the North Pacific and North Atlantic representatives. 



Following is an arrangement of the genera which is believed to express very nearly 

 the natural affinities of the various forms : — 



A. Inner claw normal (not larger or more curved than the others). No tumid "rosette" at angle 

 of mouth. 

 a 1 . Mental apex much nearer to tip of bill than to nostril ; carotid single (double in all other 

 Alcidce, so far as known). 

 Sub-family AllinjE. 



1. Alle. Bill short and very broad, the width at the base about equal to the depth and to 



the distance from the nostril to the tip. Nasal operculum completely exposed. Gonys 

 very short, being less than the width of the space between the mandibular rami at a 

 point immediately beneath the nostril. Size small (wing less than 5.00 inches). 

 a 2 . Mental apex much nearer to nostril than to tip of bill. 



4 1 . Sub-family Alcin.«. Nasal fossae completely tilled with dense velvety feathering, extend- 

 ing to or beyond anterior end of nostrils. 

 c 1 . Bill very deep, the culmen very strongly convex, the maxilla (sometimes mandible 

 also) with very distinct obliquely transverse grooves. Tail graduated, the feathers 

 pointed. (Alcem.) 



2. Plautus. Largest of the Alcidce. Wings rudimentary, not admitting of flight. Bill equal 



to the head in length, the mandible with numerous transverse sulcations. 



3. Alca. Size medium. Wings well developed, admitting of sustained flight. Bill much 



shorter than head, the mandible with but one or two well-defined sulci (or none). 

 c 2 . Bill more slender, the culmen slightly or gently convex, both mandibles destitute of 

 transverse grooves. Tail rounded, the feathers not pointed. ( UrieceS) 



4. Uria. Size of Alca. 



6 2 . Sub-family Phalerinte. Nasal fossa? only partly feathered, the feathering never reaching 



anterior end of nostrils, the nasal operculum always completely exposed. 



c 1 . Bill slender, compressed, nearly as long as the head, the culmen straight to near the 



tip, where abruptly decurved ; gonys nearly straight, ascending to the tip from the 



angle, which is situated nearer the tip than the base of the mandible. Loral apex 



forming an acute angle. (Gepphem.) 



