DUTCH BORNEO-EXPEDITION. 175 



eyebrow; a young, not yet fullgrown female with white 

 bill and casque, which latter is but faintly developed, and 

 ashy gray eyebrow, and moreover what I should call 

 a nearly adult female (the sex is thoroughly stated) with 

 black bill and casque, and hardly any trace of a gray 

 superciliary stripe, and the naked skin round the eye and 

 at the base of the lower mandible dark flesh-color (N° 1392 

 from Poelau), and an adult female (N° 78) from the Upper 

 Mahakkam, with black bill, well-developed black casque 

 and very distinct gray superciliary stripe. — Iris in adult 

 and young birds of both sexes reddish brown, bill in adult 

 males yellowish white with black basal edge, in the adult 

 female black, in young birds of both sexes white ; feet 

 dark greenish gray. 



Salvadori, in his Uccelli di Borneo, followed Blyth and 

 others in separating the black-billed birds as a distinct 

 species, a supposition which is followed by Vorderman in 

 his above quoted contribution to the Ornithology of Sumatra. 

 I cannot agree with this supposition, but yield to the 

 opinion of Schlegel's who, in his Catalogue of the Bucerotes, 

 p. 7, considers the black-billed birds the adult females of 

 Buceros mnlayanus, and the white billed adult birds as the 

 males, while young birds of both sexes should have the 

 bill white. This latter supposition is not in contradiction 

 with the four young birds in the Leydeu Museum, which 

 all have the bill white. Mr. Grant, in his Catalogue of the 

 Bucerotes in the British Museum (Vol. XVII, p. 369) seems 

 not to agree with the opinion of Schlegel's, as he says 

 that the only diiference between male and female is to be 

 found in the color of the superciliary stripe, which should 

 be white in the male and gray in the female. The black 

 bill is considered by him to indicate a transitional stage 

 of immaturity to be found in both sexes, while young birds 

 of both sexes should have white bills. As to the supposi- 

 tion of the black bill being representing a stage of imma- 

 turity, I cannot agree with Mr. Grant, nor can I consider 

 the color of the superciliary stripe as a characteristical of 



Notes from the Leyden Miuseum, Vol. XXI. 



