144 ELEMENTS OE OBNITHOLO&Y. 



the Humming-bird) may be called " tenuirostral." * If there 

 is a notch or tooth-hke process at the side, then such a bill is 

 said to be dentirostral. A bill which is bent up towards the 

 end, as in the Avocet, is termed recurved, while the opposite 

 condition is deeurved, as in the Curlew. In one genus of crook- 

 billed Plovers of New Zealand (Anarhynchus), the bill is, as 

 before said t, bent laterally. 



Before noting the terminology used to denote the parts and 

 condition of either mandible, a few words may be said as to 

 the covering of the hill, which will especially relate to the 

 maxilla. In the immense majority of instances the bill is 

 entirely hard and horny, and the investment of either jaw is 

 in one piece. In some Birds, however, as in the Petrels J, it 

 may be in several pieces, and these may be moulted like the 

 feathers, so that they form part of the summer dress, and con- 

 stitute a secondary sexual character, as is the case in the 

 Puffins §. Such bills are said to be deciduous or cadvcous. 



The bills of Birds are often marked with ridges proceeding 

 in this or that direction, and such are called carinate or striate, 

 if the ridges are pretty straight. A bill, on the contrary, is 

 said to be rugose or corrugated if the prominences form rather 

 irregular wrinkles than ridges. If the bill is marked with 

 linear depressions instead of ridges, it is termed " sulcate,'" each 

 groove being a sulcus or furrow. If the depressions are not 

 elongated, but are little rounded ones or pits, the biU is called 

 punctate. 



Instead of being all hard as horn, a bill may be of rather 

 leathery texture, as in the Ducks, or invested with a sort of 

 skin and very sensitive towards the tip, as in the Woodcock. 

 The bill may be hard towards the tip, but notably softer at the 

 base, as in that in^most Pigeons and Plovers. In Parrots and 

 Hawks the base of the bill is clothed by a peculiar wax-hke 

 investment called a cere, and this sometimes bears feathers. 

 Sometimes the bill bears very large, soft, fleshy processes, and 

 then it is said to be carunculate. If the processes are smaller, 

 like warts, the bUl is termed papillose, the warts being named 

 papillce. 



Not only is the lower jaw moveable, but the upper one is so in 

 a slight degree, though this is hardly noticeable, save in Parrots, 



* See ante, p. 100. t See ante, p. 58. 



I See ante, p. 31. § See ante, p. 25. 



