EXTERNAL PARTS OF BIRDS.— THE BILL. 105 



among exotic birds ; to tiiese, however, I cannot even allude by name. Peculiarities of nasal 

 feathers, and others around base of bill, are noticed below. Forms of crests are illustrated by 

 many figures given passim in the present work. 



2. OF THE MEMBERS: THEIR PARTS AND ORG ASS. 

 I. THE BILL. 



The Bill (Lat. rostrum) is hand and mouth in one : the instrument of prehension. As 

 hand, it takes, holds, and carries food or other substances, and in many instances, feels ; as 

 mouth, it tears, cuts, or crushes, according to the nature of the substances taken; assuming 

 functions of both lips and teeth, neither of which do any recent birds possess. An organ thus 

 essential to a prime function of birds, one directly related to their various modes of life, is of 

 much consequence in a taxonomic point of view ; yet its structural modifications are so various 

 and so variously interrelated, that it is more important in framing genera than families or or- 

 ders; more constant characters must be employed for higher groups. The general shape of 

 the bill is referable to the cone. This shape combines great strength with great delicacy ; the 

 end is fine to apprehend the smallest objects, while the base is stout to manipulate the largest. 

 But in no bird is the cone expressed with entire precision; and, in most, the departure from 

 this figure is great. The bill always consists of two, Upper and Under or Lower 



Mandibles (fig. 26), which lie, as their names indicate, above and below, and are sepa- 

 rated by a horizontal fissure — the mouth. Each mandible consists of certain projecting skull- 

 bones, sheathed with more or less horny integument in place of true abode f (j 

 skin. The framework of the Upper Mandible is (chiefly) a bone 

 called intermaxillary, or better, premaxillary . In general, this is a 

 three-pronged or tripodal bone running to a point in front, with the 

 uppermost prong, or foot, implanted upon the middle of the forehead, 

 and the other two, lower and horizontal, running into the sides of the 

 skull in front. The basis of the Under Mandible is a compound 

 bone called inferior maxillary or inframaxillary ; it is U- or 

 V-shaped, with a point or convexity in front, and prongs running to 

 either side of base of skull behind, to be there movably hinged, a, side of upper mandible ; 6, 

 These two bones, with certain accessory ones of the upper mandi- noS^(BerbelJw)Trgapl' 

 ble, as palate bones, etc., together with the horny investment, con- or wliole commissural line; <?, 

 stitute the Jaws. Both jaws, in birds, are movable; the under, by T^^^\eoi'l^r^nlh\ Ha- 

 the joint just mentioned ; the upper, either by a joint at, or by elas- mus of under jaw ; j, tom'iaof 



ticity of bones of, the forehead ; and by a singular muscular and bony ""'^^l". mandible (the refer- 

 . *' ° •' ence lines e should have been 



apparatus m the palate, further notice of which is given beyond, drawn to in<iicate the corre- 

 under head of Anatomy (Osteology). Motion of the upper mandi- sponding tomia of upper man- 

 . , dible): k, angle of gonys; /, 



ble IS freest m rarrots, where both fronto-maxillary and palato- gonys; ?«, side of under man- 

 maxillary sutures exist. When closed, the jaws meet and fit along ^'^l®: "- tips of mandibles, 

 their apposed edges or surfaces, in the same manner and for the same purposes as lips and teeth 

 of man or other vertebrates. All Ijills, thus similarly constituted, have been divided into 



Four Classes, representing as many ways in which the two mandibles close upon each 

 other at the end: 1. Epignathous (Gr. eVt, epi, upon, yvddos, gnathos, jaw) way, plan, or 

 type, in which the upper mandible is longer than the under, and its tip is evidently bent dovni 

 over the tip of the lower. 2. Hypognathous (Gr. vno, hupo, under), in which the lower man- 

 dible is longer than the other. .'}. Raragnathoxis (Gr. napa, para, at or by), in which both 

 are of about equal length, and neither is evidently bent over tlie other. 4. Metagnathous (Gr. 



k J i 



Parts of a Bill. 



