BUCEROTIDJE. 141 



lashes. The sexes are as a rule alike in plumage, but often differ 

 in size, in the form of the casque, and in the coloration of the soft 

 parts. 



The Hornbills are a very well-marked family found nearly 

 throughout the Ethiopian and Oriental regions and occurring also 

 in the Papuan subregion. They are especially remarkable for 

 their nidification, the account of which was long regarded as a 

 fable, but has now been confirmed by numerous observers. A 

 hole in a tree is selected, and then the female, usually with the aid 

 of the male, encloses herself and shuts up the orifice with the 

 exception of a narrow vertical slit, by means of earth mixed with 

 the birds' own droppings. In some cases, as Aceros nepalensis and 

 Lophoceros birostris, the droppings alone are used, and the process 

 of enclosure is then performed by the female from within the nest. 

 She is thus enclosed before she begins to lay, and apparently 

 remains in the hole till the young, which are naked when they 

 leave the egg, are fledged, being fed all the time by the male 

 through the slit left in the enclosing partition, which just allows 

 room for the bird's bill to be pushed through. The eggs are white 

 when laid, but generally become discoloured during incubation. 



All Oriental forms belong to one subfamily. By Europeans in 

 India Hornbills are commonly, but incorrectly, called " Toucans." 

 The true Toucans (Rhamphastidce) are peculiar to South America, 

 and are allied to the Barbets. 



Key to the Genera. 



a. Casque, when present, cellular within ; bill 



considerably curved; hind neck and 

 middle of back feathered. 

 a. Casque large in adults, as high as upper 



mandible or higher, 

 a". Casque broad, concave above, ending 



anteriorly in two points DICHOCEROS, p. 142. 



b". Casque compressed, ending in a single 



point ANTHRACOCEROS,P. 143. 



b'. Casque moderate or small or wanting. 

 c 1 ' Casque low, broad, rounded above, 



composed of transverse ridges RHYTIDOCEROS, p. 146. 



d". No casque ; oblique ridges at side of 



base of upper mandible : size large . . ACEROS, p. 149. 

 e". Casque small, compressed, its upper 



edge curving down in front. 

 a 3 . Crest moderate, of ordinary feathers. 



a 4 . Chin and throat naked ANORRHINUS, p. 150. 



6 4 . Chin and throat feathered PTILOLJEMUS, p. 151. 



b 3 . Crest very large, loose-textured . . BERENICORNIS, p. 153. 

 /". Casque small, compressed and pointed, 

 or wanting ; no ridges on side of bill : 

 size of birds small , , . , LOPHOCEROS, p. 154. 



b. Casque solid in front ; bill nearly stra-'ght ; 



neck all round and middle of back naked ; 



middle rectrices very long RHINOPLAX, p. 158. 



