518 



THE DIVING BIRDS — TYGOPODES. 



Hab. Whole Pacific coast of North America, from the Aleutian Islands south to Sau Diego, 

 Cal. ; breeding as far south as the Farallones. 



Sp. Char. Adult : Above, entirely uniform jilumbeous black ; under part and sides of the 

 head, with fore part and sides of the neck, plumbeous, blending gradually into the blackish of 



P. aleuticus. 



the pileum and nape ; a white spot on the lower eyelid. Lower parts, from the jugulum back, 

 immaculate white, the sides, beneath the wings, and the femoral region plumbeous. Bill black, 

 the basal third of the mandible yellowish or pale colored ; iris white ; legs and feet bluish and 

 dusky in life, bro^\^lish dusky in the dried skin. Young : Apparently similar to the adult. 



Total length, 8.00-9.50 inches ; extent, 16.00-18.50 ; wing, 4.75-5.25 ; tail, 1.50-1.75 ; 

 culmen, .75 ; depth of bill at base, .40 ; tarsus, 1.00 ; middle toe, Avith claw, 1.40. 



f 



The only seasonal changes in this very plainly colored species consist apparently in the wrink- 

 ling or corrugation of the nasal shield, especially on top, in the breeding-season. 



The Aleutian Auk was not met with by Mr. Dall among the Aleutian Islands, nor 

 by Mr. Elliott among the Prybilof Islands. It is an oceanic species, and is presumed 

 to be an inhabitant of both shores of the Pacific Ocean. 



Dr. Cooper informs me that all the specimens of this bird Avhioh he has obtained 

 are considerably larger than the measurements given by IMr. Cassin. He found two 



