so 
ON THE CLASSIFICATION OF BIRDS. 
they are, nevertheless, solid, and proceed from the front 
of the head. This process in the cassowary, is repre- 
sented in a most remakable way in the rhinoceros ; 
and if the circles of the groups which contain these 
animals are compared, it will be found that they mu- 
tually represent each other. The other naked append- 
ages found on the heads of birds, are always fleshy, 
and are attached either to the front of the head, as 
in the turkey, or on the sides of the mouth, as in the 
cock. Rasorial types, more than any other, furnish 
us with these unusual deviations from the ordinary ap- 
pearance of birds : several examples, however, occur 
in the grallatorial form, as in the genus Casmorhyn- 
chus among the chatterers or fruit-eaters, the Fsarianre,. 
the Ceblepyrus lohatus, the aberrant forms of tlie Cha- 
radrmdfn, and the different grallatorial sub-genera of 
the Musricapidai ; none of which, by the most minute 
analysis, can be reduced to rasorial types. There is a 
peculiarity, nevertheless, among these, which deserves 
notice ; for the greater part possess only a naked skin 
round the eye, similar to that in the genus Perspicilla 
{fiy. 11.) among the waterchats. The only natatorial 
birds we can recoUect as 
having naked appendages, 
are the lobed duck of New 
Holland and the common 
Muscovy duck: there is 
one example in the tenui- 
rostral tribe, and none in 
the fissirostral. 
( 39 .) Chests are the most beautiful appendages to the 
heads of birds; and give to those, which are even of the 
plainest colours, an imposing and attractive appearance. 
The use of the crest is twofold : in most birds so distin- 
guished, it is chiefly an ornament, given as a mark of 
distinction, almost exclusively, to the male ; in others, it 
not only is ornamental, but useful as a sort of defence. 
To explain this novel assertion, we can safely say that 
many are the beautiful crested woodpeckers of the 
