EXTERNAL PARTS OF BIRDS. — THE BILL. 109 



there is a promiuence, more or less marked (fig. 26, k) ; this is the gonys (corrupted from 

 Gr. yovv, gonu, a kuee; hence, any similar protuberance). That is to say, this point is gonys 

 proper (sometimes called angle of the gonys or gonydeal angle) ; but the term gonys is extended 

 to apply to the whole line of union of rami, from gonys proper to tip of under mandible ; and in 

 descriptions it means, then, tinder outline of bill for a corresponding distance (fig. 26, 1). This 

 important term is constantly used in describing birds.* Gonys is to under mandible what a 

 keel is to a boat ; it is the opposite of ridge or culmen of upper mandible. It varies greatly 

 in length. Ordinarily it forms one-half to three-fourths of the under outline. Sometimes, as 

 in conirostral birds, a Sparrow for example, it represents nearly all this outline ; while in a 

 few birds it makes the whole, and in some, as the Puffin, is actually longer than the lower 

 mandible proper, because it extends backward in a point. Other birds may have almost no 

 gonys ; as a Pelican, where the rami only meet at the extreme tip, or the whole Duck family, 

 where there is hardly more. As the student must see, length of gonys is simply a matter of how 

 extensive is fusion of 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 interramal space is complementary to length of gonys ; sometimes it runs to tip of bill, as 

 in a Pelican, sometunes there is next to uone, as in a Puffin ; while its width depeuds upon 

 degree of divergence, and straightness or curvature, of the rami. This space may be occupied 

 by naked skin of the floor of the mouth, or partly or completely feathered. The surface be- 

 tween tomium and lower edge of rami and gonys together is side of under mandible (fig. 26, m). 

 Each mandibular ramus is sometimes called gnathidium ; and that portion of the rami which 

 corresponds to length of gonys is known as myxa. The most important feature of the 



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

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

 — highest middle lengthwise line of bill; it begins where feathers end on the forehead, and ex- 

 tends to tip of upper mandible. According to shape of bill it may be straight, convex, con- 

 cave, or even somewhat 02 -shaped; or double-convex, as in the Tufted Puffin : but in most 

 cases it is convex, with increasing convexity toward the tip. Sometimes it rises up into a thin 

 elevated crest, as in the genus Crotophaga, and in Puffins (Fratercula) , when the upper man- 

 dible is said to be keeled, and the culmen itself to be cidtrate ; sometimes it is 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 convex and sloping sides of upper mandible (fig. 26, a). In a great many 

 birds, especially those with depressed bill, as all Ducks, there is really no culmen ; then the 

 median lengthwise line of surface of upper mandible takes place and name of culmen. The 

 culmen generally stops about opposite the proper base of the bill ; then the feathers sweep 

 across its end, and downward across the sides of the upper mandible, usually also obliquely 

 backward. Variations in both directions are frequent ; feathers may run out in a point on cul- 

 men, shortening the latter, or a culmen may run up the forehead, parting feathers ; either in a 

 I)oint, as in Rails and Gallinaceous birds, or as a broad plate of horn, as in Coots and Gallinulcs. 

 A culininal point between feathers of the forehead forms an angulus frontalis ov frontal angle ; 

 and the same terms are used for extension of feathers in a point on the culmen. The lower 

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

 and h(irny. 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 which each nostril opens. 

 The ujjper prong of the intermaxillary bone is usually separated some way from each lateral 



* The word gonys originated with Illiger in 1811. It is a mistake for genys (Gr. yivv<;, genus), meaning lower jaw or 

 chin. But it is firmly established in ornithology, and supplied with a fictitious etymology to suit, as in my text. (See, 

 for example, Sundevall, Teiitamen, or the Century Dictionary.) The adjective gonydeal is a monstrous abortion of a 

 •word, but in good current u.sage. 



