ALCID^ — THE AUKS — SYNTHLIBORAMPHUS. 503 



There is apparently something not yet understood in tlie relationship between this bird and 

 B. hiipoleucus, and it would not be at all surprising if the two shcjuld prove to be different phases of 

 one species. Dr. Cones (" Pr. Philad. Acad." 1868, p. G5) suggests the possibility of Craverii being 

 the young of hiipoleucus ; but Dr. T. H. Streets ("Bull. U. S. Nat. Mus." No. 7, 1877, pp. 32 33) 

 proves this nut to be the case, and substitutes the theory of the latter beiu" the winter the former 





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the summer, plumage of the same species. His remarks are as follows : " Dr. Coues alludes to the 

 ' bare possibility ' that Craverii was the young of hypolemus — a supposition disproved by finding 

 it breeding. B. Craverii can only be referred to hypoleucus now upon the assumption that the latter 

 is the winter plumage of the former, as all specimens which have come to hand thus far with pure 

 white lining of the wings were taken in winter, as far as known. Such an assumption would not 

 be widely at variance with the known characters of the seasonal changes of plumage in some 

 members of this family, but remains to be proven. Pending this determination, Craverii should be 

 recognized as a good species." 



To the above we have to say that although no date is given on the label of the type specimen 

 of B. hypoleucus, it is apparently a midsummer bird, the plumage being e.vceedingly worn or 

 weather-beaten, which would hardly be the case had it been killed in winter. 



Genus SYNTHLIBORAMPHUS, Bkandt. 



Synthliboramphus, Brandt, Bull. Ac. St. Peter.sb. II. 1837, 347 (type, Alca antiqua, Gmel. ). 



Char. Size rather small (wing about 5.50 inches). Bill much shorter than the head, very 

 compressed, but the culmen comparatively broad ; culmen regularly convex ; gonj's lengthened 

 (more than half as long as the culmen), nearly straight ; nasal fossae very small, the oval nostrils 

 situated near their centre ; color chiefly plumbeous above and white beneath, the head and neck 

 pied black and white. 



Com. Char. Above plumbeous, beneath white. Summer plumage: Chin and part or whole of 

 the throat dusky ; top of the head with a broad white stripe on each side ; entire sides, from neck 

 to flanks, sooty blackish. Winter plumage : Similar, but whole throat white, the chin plumbeous ; 

 white stripes on top of head absent ; sides and flanks white, striped with slaty. 



Of this genus two species are known, distinguished as follows : — 



1. S. antiquus. Never crested. Summer plumage : Chin and whole throat sooty black, with 



a convex lower outline. Winter 2)lumage : Auricular region crossed by a horizontal broad 

 bar of dusky. 



2. S. ■wumizusume. Crested in the breeding-season. Summer plumage : Forehead with 



a loose crest of several narrow, much elongated, nearly straight feathers, e.xtending back 

 toward the occiput ; lores, orbital region, cheeks, chin, and upper half of the throat, 

 velvety plumbeous, with a truncated lower outline. Winter j^lurnage : Auricular region 

 entii-ely white. 



