2Q92 The Zoologist — September, 1870. 



by dusky, especially on the wing and tail-coverts, and lower back. 

 Forehead, crown, nape and back of neck, sooty black, entirely 

 unrelieved by white streaks, or with only traces of the latter on the 

 sides of the occiput. Eyelids sometimes largely white. No black 

 on the throat or chin ; traces of it in a dusky mottling about the base 

 of the bill. White of under parts extending on sides of head below 

 and behind nearly to the eyes, and far around on the sides of the nape, 

 so that only a median nuchal line is left blackish. Sides of body 

 under the wings not pure black, but merely dusky plumbeous, and 

 this not continuous on the feathers over the flanks, these being in 

 some part white, producing a white and plumbeous variegation. The 

 line of this dusky plumbeous hardly extends in front of the wings to 

 the sides of the neck. Under parts white, as before, the bases of the 

 inner webs of the primaries rather more white than in the adult. 



The above described differences between the adult and young are 

 very decided, and might suggest a distinction of species, were not 

 various means between the extremes forthcoming. Beyond these 

 variations in plumage the species is very constant in characters, with 

 the exception of the bill. This differs a good deal as to its size and 

 shape ; but nevertheless usually preserves the specific characters 

 which distinguish it from that of Wurmizusume. Thus the difference 

 in length between the bills of two perfectly mature examples, 

 absolutely identical in plumage, and in all other respects, save length 

 of bill, amounts to a tenth of an inch along the culmen. This 

 difference being accompanied by a corresponding difference in 

 depth and width, gives a readily appreciable difference in shape of 

 the bill. 



The only species to which the present bears any special resemblance 

 is Wurmizusume. The comparative characters of the latter are dwelt 

 upon at length in the article immediately succeeding. 



It is barely possible that the bird here described is not the veritable 

 Alca antiqua, Gm. (" Antient auk " of Pennant). In the description of 

 these authors the upper parts are said to be dusky or sooty black, 

 whereas, as will be seen by the description, the subject of the present 

 article has these parts clear plumbeous. But we have just seen that the 

 youngof the present bird has the upper parts decidedly darker and duller 

 than the adult; in fact tending,especially upon the wings and lower back, 

 to dusky. The limits within which the species is known to vary in this 

 respect are sufficiently wide to allow its reference to the bird of Pennant, 

 Latham and Gmelin ; especially when it is remembered that the particular 



