SPECIAL PARTS OP THE UNDER MANDIBLE. 27 



(L. caro, flesh, diminutive carunculus, little bit of flesh). Various linear 

 depressions, often but not always associated with carinfe, are grooves or sulci 

 (L. sulcus, a furrow) and the bill is then sulcate. Sulci, like carince, are of 

 all shapes, sizes and positions ; when very large and definite, they are some- 

 times called canaliculi, or channels. The various knobs, "horns," and large 

 special features of the bill cannot be here particularized. Any of the fore- 

 going features may occur on both mandibles, and they are exclusive of that 

 special mark of the upper, in which the nostrils open, and which is consid- 

 ered below (§ 51). We have still to notice the special parts of either 

 mandible ; and will begin with the simplest, the 



§ 49. Under Mandible. In the majority of Ijirds it is a little shorter 

 and a little narrower and not nearly so deep as the upper ; but sometimes 

 quite as large, or even larger. The upper edge, double (2. e. there is an 

 edge on both sides), is called the mandibular tomium (Gr. temnein, to cut; 

 fig. 5,y), as far as it is hard; this is received against, and usually a little 

 within, the corresponding edge of the upper mandible. The prongs already 

 mentioned (§ 44) are the mandibular rami (pi. of L. ramus, a branch; fig. 

 5, i) \ these meet at some point in front, either at a short angle (like >) or 

 with a rounded joining (like t) ). At their point of union there is a promi- 

 nence, more or less marked (tig. 5, 7u) ; this is the gonys (corrupted from 

 the Gr. gonu, a knee ; hence, any similar protuberance). That is to say, this 

 point is gonys proper ; but the term is extended to apply to the whole line of 

 union of the rami, from gonys proper to the tip of the under mandible ; and 

 in descriptions it means, then, the under outline of the bill for a corres- 

 ponding distance (fig. b,l). This important term must be constantly held 

 in mind. The gonys is to the under mandible what the keel is to a boat. 

 It varies greatly in length. Ordinarily, it forms, say, 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 puflin, is actually longer than the lower 

 mandible proper, because it extends backwards in a point. Other birds 

 have almost no gonys at all : as a pelican, where the rami only meet at the 

 extreme tip, or in the whole duck family, where there is hardly more. 

 As the student must see, the length of the gonys is simply a matter 

 of the early or late 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 

 interramal space (§ 41, c) is complementary to length of gonys: some- 

 times it runs to the tip of the bill, as in a pelican, sometimes ther-e is next 

 to none, as in a puffin ; while its width depends upon the degree of diver- 

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

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

 under mandible (fig. 5, «i). The most important feature of the 



§ 50. Upper Mandible is the cidmen (Lat. for top of anything; fig. 5, 

 b). The culmen is to the upper mandible what the ridge is to the roof of a 



