520 



THE DIVING BIRDS — PYGOPODES. 



compressed vertical process of the nasal shield, characteristic of the breeding-season. When the 

 latter is cast, the upper outline of the cere is nearly straight, and depressed decidedly below the 

 level of the base of the culnien. Head ornamented by four (two on each side) longitudinal series 

 of filamentous white feathers. Plumage dull-grayish dusky above, wliitish below, the under side 

 of the head and neck brownish gray. 



C. monocerata, summer adult. 



Of this remarkable genus but one species is known ; this having given ornithologists much 

 trouble before the deciduous character of the nasal horn and mandibular process was fully under- 

 stood ; the same species in winter plumage, with these appendages absent, being referred to a 

 different genus (" Sagmatorhina"). 



Cerorhyncha monocerata. 



THE HORN-BILLED AUK. 



Aha monocerata, Tall. Zoog. Rosso-As. II. 1826, 302, no. 414. 



Cerorhina monocerata, Cass, in Baird's B. N. Am. 1858, 905. — Bawd, Cat. N. Am. B. 1859, no. 717. 



Ceralorhyncha monocerata, (/hues, Pr. Ac. Nat. Sci. Philad. 1868, 28, figs. 1, 2. 



Ceratorhina monocerata, Coues, Key, 1872, 341 ; Check List, 1S73, no. 620; ed. 2, 1882, no. 857. — 



Ridgw. Nom. N. Am. B. 1881, no. 620. 

 Phaleris ccrorhynca, Bonap. Zool. Journ. 1827, 53. 

 Cerorhinca octidentalis, Bonap. Ann. Lye. N. Y. (Synop. N. Am. B.) IV. 1S28, 428. — Ninr. Man. 



II. 1834, 538. 

 Ceratorhina occidentals, Am, Orn. Biog. V. 1S39, 104, pi. 402, fig. 5. 

 Uria octidentalis, Aud. B. Ami. VII. 1844, 364, pi. 471. 



Cerorhina orientalis, Brandt, Bull. Ac. St. Petersb. II. 1837, 348 (lapsus calami for occidentalism). 

 Chimerina cornuta, Eschscholtz, Zool. Atl. III. 1S29, 2, pi. 12. 

 Cerorhina SucJtfeyi, I 'ass. in Baird's B. N. Am. 1858, 906 (adult without knob on bill). — Bawd, 



Cat. X. Am. B. 1859, no. 718. 

 Sagmatorhina Suckleyi, Coues, Pr. Ac. Nat. Sci Philad. 186S, 32, figs. 4, 5 (bill). 

 The Horn-billed Guillemot, Cass. & Bawd, 11. c. 



Hab. Coasts and islands of the North Pacific, breeding as far south as California (Farallon 

 Islands) and Northern Japan ; in winter, as far as Lower California. 



Sp. Char. Adult, breeding plumage : Entire upper parts dull brownish black, the feathers some- 

 times with paler or grayish brown tips ; lateral and under parts of head and neck, jugulum, and 



