550 CLASS AVES. • 



edged with small tubercles, supporting the lashes in its entire 

 circumference. The upper is evidently mobile ; the third 

 lid, or nictitating membrane, is very small, and the parrots 

 are never seen to make use of it. The pupil is round, and 

 not situated exactly at the centre of the iris, but more inward ; 

 so that the iris is a little broader on its external than on its 

 internal side. The colour of this last varies according to the 

 species ; but it is generally remarked to grow deeper with 

 increasing age. A peculiar character in the parrots is the 

 ability of contracting the pupil, more or less, independently 

 of the action of the light, when they turn their attention to 

 any object — when they feel any sudden internal movement, 

 such as fear or anger — or even when ihey are in a sportive 

 mood. These birds are evidently diurnal. 



The aperture of the ear is oval and small, especially if 

 compared with that of the ululse ; it is directed obliquely 

 forward, and constantly covered with the feathers. 



In certain birds of this genus the cheeks are naked of fea- 

 thers, and covered with a white farinaceous powder, as is 

 remarked in the maccaws ; or the skin is coloured, as in the 

 microglossi. In others the circumference round the eye is more 

 or less divested of feathers, and also covered with a sort of 

 farina. This appears to be an epidermic production, and is 

 very abundant on other parts of the skin of these birds, whose 

 plumage, when they shake it, gives out a considerable quan- 

 tity of white dust. In no species are fleshy caruncles to be 

 found. Some, as the cockatoos, many psittaculi, &c., have 

 the head ornamented with long and slender plumes, which 

 can be elevated in the form of a tuft, or crest, according to 

 the inclination of the bird, but which, in general, are reclined 

 along the neck. 



The neck , in general, is but moderately long ; sometimes it 

 is even short, and tolerably thick ; still, when the parrots 



