176 THE VICTORIAN NATURALIST. 



of green in the young and red in adult stage ; humeral feathers 

 faint dark brown with a few blues, instead of true blue in young 

 and old birds ; back, upper surface of tail, and wing coverts 

 medium deep yellow, instead of green in young and red with 

 black in adult bird. 



The pronounced peculiarity of this variety is the prevalence of 

 yellow and red instead of green and red in the young bird or red 

 in the adult. 



The green colour is probably due to an admixture of a yellowish 

 pigment called psittacofuloine. Hitherto a really green colour 

 has been found only in the Touracoes (Dr. J. S. Kingsley). 

 Although this species shows blue in the true form and violet in a 

 metamorphosed bird, there are, it is believed, no such pigments 

 known. The dark brown to yellow on the shoulders of this 

 specimen would give the blue appearance of the normal plumage 

 if the surface structure of the feathers was placed in a certain way, 

 but because the cells are incorrectly placed the blue does not 

 show. The blue is an objective structural colour — that is to say, 

 it is brown with certain superimposed transparent cells which give 

 the brown the appearance of blue. Brown without these cells is 

 an absorption colour. To test this thoroughly, wet a green bird 

 with water when it will appear brown, because the colourless cells 

 which overlap the pigment in each feather have been disarranged. 

 Buller (" Trans. N.Z. Institute ") mentions that if you beat a 

 green feather of a parrot with a hammer it will appear yellow, 

 such as this one is without the hammering, or if you treat a blue 

 feather in the same manner brown will be the result. An experi- 

 ment was made with a blue macaw, which was turned into a 

 brown one. 



I should like to mention here an adult bird with a malformed 

 bill occupying the same perch in our museum. The lower 

 mandible curves upwards and inwards, with the end and tip on a 

 plane with the crown. The upper mandible has a more cres- 

 centic curve, and for half an inch at the extremity lies along the 

 cheek blue. Its length is nearly 5 inches. 



(6.) In collection of Mr. A. Coles, jun., Melbourne. 



Indistinct blue instead of strong blue in the specified parts of 

 normal bird, while the green is yellowish-green instead of true 

 green ; breast, forehead, and under tail coverts crimson. 



(c.) In National Museum. P. nigrescens, Ramsay. 



In the "Tabular List of Australian Birds," 1888, page 34, 

 Dr. Ramsay refers to this bird as a variety of Platycercus pen- 

 nantii, now elegans, and found in the Bellenden-Ker Range, North 

 Queensland, but up to 1891 the British Museum authorities were 

 evidently unacquainted with it. Dr. Ramsay mentions the 

 appearance of a few violet feathers on the chest, which is a 



