160 



the escape of the air is obstructed at the glottis, and in this 

 case the pressure within the trachea would be intelligible. 



Pelecanidcc. The differences between the sexes in the 

 pelicans are generally slight or absent; but in one American 

 species there is an interesting peculiarity in the male. 

 This is the White Pelican, P. erythrorhynclms, of North 

 America, in which a longitudinal vertical plate of horn is 

 developed in the upper mandible in the breeding season. 

 This excresence is about an inch high and two or three 

 inches long, and situated near the middle of the length of 

 the bill. The most interesting fact about it is that it is 

 bodily shed at the end of the breeding season, about the 

 month of May. 1 Mr. Eidgway ascertained this fact from 

 observation of the birds at Pyramid Lake in Nevada 

 where they breed, but unfortunately he does not give 

 any evidence as to the use made of the excresence before 

 it drops off. Audubon 2 expressed his belief that the bird 

 uses the apparatus as a means of attack and defence 

 when engaged with its rivals in the love season ; and the 

 same opinion is given in Birds of North America by Baird, 

 Cassin, and Lawrence. Probably the opinion is correct, and 

 this is another instance of epidermic hypertrophy taking 

 place at the breeding season in response to irritations which 

 are only applied at that season. We may assume that the 

 excresence now develops partly by heredity, though this has 

 not been proved by direct experiment. 



Batitce. Darwin says of the African Ostrich that the 

 male is somewhat larger than the female and has finer 

 plumes, with more strongly contrasted colours ; that never- 

 theless he performs alone the duties of incubation. This 

 statement is made on the authority of Mr. P. L. Sclater ; and 

 on the authority of Captain Musters {At Home with the 



1 Ibis, 1869, p. 350. 

 2 Ornithological Biography, vol. iv. 



