COLYMBUS ADAMSI. 



(WHITE-BILLED DIVER.) 



Cepphus torquatus, Pall. Zoogr. Ross.-As. ii. p. 340 (1811, partim). 



Cohjmbus glacialis (nee Linn.), Middendorff, Sib. Reise, ii. part 2, p. 238 (1851). 



Cohjmbus adamsii, G. R. Gray, P. Z. S. 1859, p. 167. 



Cohjmbus torquatus, var. adamsii, Coues, Key N.-Am. Birds, p. 234 (1872). 



Vrinator adamsii (Gray), Stejneg. Proc. U. S. Nat. Mus. v. p. 43 (1882). 



Cohjmbus torquatus adamsi, Coues, 2nd Check-list, no. 841 (1882). 



Cohjmbus torquatus, b. adamsii, Coues, B. of N.-W. p. 720 (1874). 



Colymbus adamsi, G. E. Gray, Hand-1. of B. iii. p. 92. no. 10736 (1871). 



Bolsclioi-Gagdra, Russian; Morskaja Gagdra, Iakutsk ; Mora Kowa on the Boganida; 

 Uvankets jouku, Tschuktsch; O-hamu, Japanese; Tu-d-lin, Eskimo. 



Figures notabiles. 

 D. G. Elliot, B. of N. Am. ii. pi. lxiii.; Collett, Ibis, 1894, pi. viii. 



Ad. ptil. <est. corpore suprk sicut in C. glaciali picturato, sed unaculis albis raajoribus, dorso irno immaculate 

 et uropygii maculis sparsis : gula creruleo-nigra violaceo tiucta : collari juguli magis conspicue striate : 

 rostro flavo-albo. 



Ad. ptil. Mem. corpore supra nigro vix guttato : uropygio immaculato : pileo, nucha et collo postico grisescenti- 

 nigris : corpore subtus albo : gula et gutture cinereo-fusco notatis. 



Juv. pileo, nucha et collo postico cinereo-fuscis : corpore supra cinereo-fusco, dorsi plumis, scapularibus et 

 tectricibus alarum conspicue cinereo marginatis : uropygio fere immaculato, sed supracaudalibus cinereo 

 apicatis : corpore subtiis albo. 



Adult in summer (Russian America). Upper parts similar to C. glacialis, except that the spots on the back 

 and wings are considerably larger, those on the back being more restricted to the middle of the back, 

 there being a space free from spots between them and those on the wings ; lower back unspotted, and 

 the dots on the rump fewer thau in C. glacialis ; shafts of the wing-feathers light horn-colour nearly 

 to the tips ; throat and collar blue-black with a violet gloss; the upper or throat-collar with fewer and 

 larger stripes ; the lower or neck -bar widest in the middle, generally smaller than in C. glacialis and 

 with larger stripes: culmen whitish yellow, longer than the tarsus, culmen and commissure straight. 

 Total length about 32 inches, culmen 4'3, gape 4 - 7, wing 15 '25, tail 2"6, tarsus 3'5. 



Adult Male in winter (Tromso Fjord, November 5th). Crown, nape, and hind neck dull blackish grey; 

 upper parts generally black, with a few white spots on the wing-coverts and one or two on the back; 

 rump unspotted; nnderparts white; the throat aud neck marked with greyish brown. 



