590 Descriptions of the Groups of Birds 



poes, it is in like manner not renewed till after the following 

 breeding season. 



The sterna of the Buceroides (hornbills and hoopoes toge- 

 ther), however, differ from those of the Halcyoides in present- 

 ing but one pair of notches posteriorly ; the single emargina- 

 tion adverted to being slight in the Buceridae (or hornbills), 

 and much deeper in the Upupidce (or hoopoes) : and the con- 

 figuration of the entire sternal apparatus, in these two fami- 

 lies, though by no means closely similar, yet mutually ap- 

 proximates more than either does to that of any other group 

 of birds, or than is observable in the analogous instance of 

 the kingfishers and jacamars among the Haley oides. I have 

 examined the skeletons of six or seven species of Buceridae, 

 which has afforded an opportunity of remarking the rigid con- 

 stancy of form maintained by the sternum and its accessories, 

 and the importance, consequently, of the character which is 

 thence derivable, as a guide to sound classification. 



Exteriorly, the Buceroides differ from the Halcyoides in 

 the absence of bright colouring, so prevalent among the lat- 

 ter, and in possessing only ten tail-feathers, whereas the others 

 have twelve ; their body-feathers have no accessory shaft. — 

 It is scarcely necessary to remind the reader that all Insesso- 

 res (auct.) which have fewer than twelve caudal rectrices, pos- 

 sess the distinctive characters of my great ordinal group Stre- 

 pitores. 



The Buceroides, finally, are confined in their distribution 

 to the eastern hemisphere. I shall now proceed to treat of 

 the two tribal families separately in detail. 



I. — Appendirostres, (or with beaks furnished with an ap- 

 pendage). The strongly characterized group of hornbills 

 contains the largest species of Strejriiores : but the superior 

 dimensions of these birds are attained, as it were, in great 

 measure by inflation ; their skeletons being excessively light, 

 and more completely permeated by air than in any other birds 

 whatever, even than the gannets, — for the phalanges of the 

 toes are hollow to their extremities. Their formidable-look- 

 ing beak is in like manner chiefly so in appearance ; and may 

 be briefly described as of large size, thick, tapering, and much 

 arched, with originally serrated edges to the mandibles, that 

 become obliterated by use, which at the same time renders 

 them irregularly jagged after their primitive edge has disap- 

 peared : this organ is also mostly provided with an extraor- 

 dinary protuberance, of varied form and size in the different 

 species, which gradually appears and enlarges, as they ad- 

 vance in age, upon the ridge of the upper mandible, till in 

 some species it almost equals in dimesions the immense beak 



