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THE RHINOCEROS HORNBILL. 
On cutting asunder the beak and helmet of a Hornbill, we shall find that the outer 
shell of horny substance is very thin indeed, scarcely thicker than the paper on which this 
description is printed, and that the whole interior is composed of numerous honey-combed 
cells, with very thin walls and very wide spaces, the walls of the cells being so arranged as 
to give very great strength when the bill is used for biting, and with a very slight expenditure 
of material. The whole structure, indeed, reminds us greatly of that beautiful bony network 
which gives to the skull of the elephant its enormous size and lightness, and which is fully 
described in the volume on Mammalia, page 598. The general appearance of the dried head 
of a Hornbill, with its delicate cellular arrangements, and its thin, polished, bony shell, 
is not unlike the well-known shell of the paper nautilus, and crumbles in the grasp almost as 
easily. 
The most common is the Rhinoceros Hornbill ( Buceros rhinoceros) ; one of the hand- 
somest is the White-crested Hornbill ( Buceros albocristdtus) ; other interesting species are 
the Crested Hornbill ( Buceros cristdtus), the Two-hoened Hoeniull ( Buceros bicornis), and 
the Woodpecker Hornbill {Buceros pica.). 
TWO-HORNED HORNBILL.— Buceros bicornis. 
Peehaps the greatest development of beak and helmet is found in the Rhustoceeos Hoen- 
bill, although there are many others which have these appendages of great size. 
As is the case with all the Hornbills, the beak varies greatly in proportion to the age of 
the individual, the helmet being almost imperceptible when it is first hatched, and the bill not 
very striking in its dimensions. But as the bird gains in strength, so does the beak gain in 
