104 GENERAL OBNITROLOGY. 



only meet at the extreme tip, or in the whole duck famUy, where there is hardly more. As 

 the student must see, the length of the gonys is simply a matter of how extensive is the fusion 

 of the rami, and that, similarly, their mode of fusion, as in a sharp ridge, a flat surface, a 

 straight line, a curve, etc., results in corresponding modifications of its special shape. The 

 interramdl space is complementary to length of gonys : sometimes it runs to the tip of the bill, 

 as in a pelican, sometimes there is next to none, as in a puflBn ; while its width depends upon 

 the degree of divergence, and the straightness or curvature, of the rami. The surface between 

 the tomium and lower edge of rami and gonys together is the side of the under mandible 

 (fig. 26, m). The most important feature of the 



Upper Mandible is the culmen (Lat. for top of anything ; fig. 26, 6). The culmen is to 

 the upper mandible what the ridge is to the roof of a house ; it is the upper profile of the bill 

 — the highest middle lengthwise line of tlie hill ; it begins where the feathers end on the fore- 

 head, and extends to the tip of the upper mandible. According to the shape of the bill it may 

 be straight or convex; or concave, or even somewhat cc -shaped ; or double-convex, as in the 

 tufted puffin : but in the great ma,jority of cases it is convex, with increasing convexity towards 

 the tip. Sometimes it rises up into a thin elevated crest, as well shown in the genus Cro- 

 tophaga, and in the puffins (Fratereula), when the upper mandible is said to be keeled, and the 

 culmen itself to be cultrate ; sometimes it is really a furrow instead of a ridge, as toward the 

 end of a snipe's bill ; but generally it is simply the uppermost line of union of the gently con- 

 vex and sloping sides of the vpper mandible (fig. 26, a). In a great many birds, especially 

 those with depressed biU, as all the ducks, there is really no culmen ; but then the median 

 lengthwise line of the surface of the upper mandible takes the place and name of culttien. 

 The culmen generally steps short about opposite the proper base of the bUl ; then the feathers 

 sweep across its end, and downwards across the base of the sides of the upper mandible, 

 usually also obliquely backwards. Variations in both directions from this standard are 

 frequent; the feathers may run out in a point on the culmen, shortening the latter, or the 

 culmen may ruii a way up the forehead, parting the feathers ; either in a point, as in the rails 

 and gallinaceo(is birds, or as a broad plate of horn, as in the coots and gallinules. The lower 

 edge (double) of the upper mandible is the maxillary tomium, as far backward as it is hard 

 and homyi The most conspicuous feature of the upper mandible in most birds is the 



Nasal Fossa (Lat. fossa, a ditch), or nasal groove (fig. 26, c), in wliicli the nostrils open. 

 The upper prong of the intermaxOlary bone is usually separated some ways from the two 

 lateral prongs; the skinny or horny sheath that stretches betwixt them is usually sunken 

 below the general level of the bill, especially in those birds where the prongs are long or 

 widely separated; this " ditch" is what we are about. It is called fossa when short and wide, 

 with varying depth ; sulcus or groove when long and naiTow ; the former is well illustrated in 

 the gallinaceous birds ; the latter in nearly all wading birds and many swimmers. When the 

 intermaxillary prongs are soldered throughout, or are very short and close together, there is 

 no (or no evident) nasal depression, the nostrils then opening flush with the level of the 

 biU. The 



Nostrils (fig. 26, d), two in number, vary in position as follows : — they are lateral, when 

 on the sides of the upper mandible (almost always) ; culmmal, when together on the ridge 

 (rare) ; superior or inferior when evidently above or below midway betwixt culmen and tomia; 

 they are basal, when at the base of the upper mandible ; stth-basal when near it (usual) ; 

 median when at or near the middle of the upper mandible (frequent, as in cranes, geese, etc.) ; 

 terminal when beyond this (very rare ; probably there are now no birds with nostrils at the 

 end of the bill, except the Apteryx). The nostrils are pervious, when open, as in nearly all 



