246 GENERAL ORNITHOLOGY part ii 



ankylosis, sometimes only by suture, with its fellow of the opposite 

 side. This union in the middle line is the symphysis (Gr. aiv, sun, 

 with ; <l>vcri<s, phwsis, growth). The line of union is externally the 

 gonys (see anted,), the length and other characters of which are 

 determined by the mode of symphysis, as is the general shape of the 

 tip of the lower mandible. The union generally makes an angular 

 A, but may be an obtuse n ; the symphysis is very short and im- 

 perfect, as in a pelican, for instance, or the opposite, as in a wood- 

 pecker and a multitude of birds. Behind the dentary, each ramus of the 

 jaw continues with pieces called splenial, angular and surangular (sp, a, 

 su); there is often a fenestra between them, by imperfection of bony 

 union, as shown in Fig. 62 or 63, /, which also sufficiently indicates 

 the relations of these parts. The articulation of the jaw with the 

 quadrate bone is furnished by a fifth piece called articular (ar) from 

 its function. As a whole the mandible is a pronged bone, forking 

 with a variable degree of divergence from its obtuse or acute point, 

 sometimes quite parallel-sided, as in a duck, oftener very open ; 

 such prongs may be straight, or variously curved or bent either in 

 the vertical or the horizontal plane ; are generally stout and stanch, 

 sometimes so slender as to' be quite flexible. The articular part, 

 always expanded horizontally, presents a smooth irregularly cupped 

 superior surface for reception of the protuberances of the foot of 

 quadrate. In general, this concave articular surface is divided into 

 an inner and outer cup separated by a protuberance, corresponding 

 to similar inequalities of the opposing surface of the quadrate. 

 Cupping of the mandibular articulation is characteristic of birds 

 as compared with mammals, in which latter the lower jaw has 

 always a knobbed articular surface (condyle). In many birds 

 the angle of the jaw is prolonged back of the articulation as a 

 posterior articular process (Fig. 63, h, 70, 71, pap), which may be long, 

 slender, and upcurved, as is well shown in a fowl, duck, or plover. 

 Such birds are said to have the " angle of the mandible recurved ; " 

 the opposite condition is " angle truncated " (cut off). Usually also, 

 an internal angular process (Figs. 70, 71, «ap) is produced inward from 

 the articular part of the jaw, as in the fowl or duck. Between the 

 dentary and articular parts, the ramus of the jaw is usually vertically 

 produced as a thin raised crest, which, when prominent, is called 

 the coronoid process ; it corresponds to the strong process so called in 

 a mammal, and relates to the advantageous insertion of the temporal 

 or masseteric muscles which effect closure of the jaw. It is scarcely 

 evident in the fowl (Fig. 62), but well marked in the duck (Fig. 63, 

 over /). At the back of the articular surface is the pneumatic 

 foramen for entrance of air, when any ; on the inner surface of the 

 ramus, about the splenial bone, is the opening conveying the vessels 

 and nerve. 



