PERCHING BIKDS. 



147 



Fig. 122. Rhinoceros Horn-bill. 



with its appendage, is not as heavy as it appears, for its 

 structure is of a light, honeycomb character. The upper 

 protuberance is hollow, and it is supposed that it serves 

 as a sort of sounding-board, to give by its reverberations 

 force to the roaring cry of the bird. There are several 

 species found in India and Africa. 



245. Of the division of the Perchers called Dentiros- 

 tres, or Tooth-billed, there are five families : the Shrikes, 

 or Butcher-birds, Warblers, Thrushes, Fly-catchers, and 

 Chatterers or Waxwings. The notch in the upper man- 

 dible which makes the tooth-like projection, 234, is not 

 always deep, and is sometimes wanting. In such a case 

 the proper place of the bird in the classification is known 

 by its resemblance in other respects to the true tooth- 

 billed species. There are some, indeed, whose charac- 

 teristics are so intermediate between the Conirostres 

 and the Dentirostres, that zoologists differ as to the 



