ELEMENTARY SKETCH OF THK OSTEOLOGY OF BIRDS. 7 



quadrate also articulates \vith the pterygoid (pt.) — a bone to 

 which we shall have occasion to refer again. 



The anterior portion of the jugal style comprizes a small 

 bone which is the homologue of the maxilla* (fig. 1, mx.) 

 of mammals, and which inferiorly expands into the so-called 

 maxillo-palatinef process (mxp.) which is very charac- 

 teristic of the bird-skull. By far the greater portion of the 

 upper jaw is formed by the two premaxill£e| (p. mx.) These 

 bones are very peculiar in shape, and are of relatively large size, 

 each being divided into three processes. Of these three processes 

 a palatine process (pi. II. fig. 1) runs along the palate towards 

 the palatines, § an ascending process (n. pmx, fig. 2) passes 

 upwards in the middle line between the nasals (na.) || while an 

 external or maxillary process forms the greater part of the mar- 

 gins of the upper jaw, and unites posteriorly with the maxilla. 

 The orbitIF (o. pi. 1.) is open inferiorly, and is bounded above by 

 the frontals, which generally send down a descending post-orbital 

 process, (pi. II., figs. I and 3, p. f.) This process may be deve- 

 loped from the alisphenoid, and in that case may be separately 

 ossified. The exterior border of the orbit is usually defined 

 by a loosely attached and frequently spongy bone, which corres- 

 ponds to the lachrymal** of mammals (fig. 2, 1.; The lachrymal 

 articulates with the nasal and frontal above, and with the max- 

 illa below. The lachrymal is frequently closely united internally 

 with the prefrontal ft which is connected with the nasal passages. 

 The lachrymal, which is often loosely articulated with the 

 frontal, is greatly developed in the Parrots and Raptorial 

 birds, and is generally spongy in the latter. In connection 

 with the frontal there may be, as in Arboricola, a chain of small 

 bones developed above the orbit, which may be called supra-or- 

 bitallX, and occasionally an infra-orbital chain may be developed 

 near the jugal arcade. 



The external nares§§ (na. pi. I.) are mainly bounded by the 

 nasals and premaxilise. 



* Maxilla, a jaw ; in mammals the bone carrying all the upper teeth behind 

 the incisor or " front" teeth. 



f The name maxillo-pallatine indicates that the process in question is given oflf 

 from the maxilla, and is in connection with the palatine. 



J Prem axilla, from prce, m front, and maxilla ; in mammals the bone which 

 is situated in advance of the maxilla and which carries the iacisor teeth. 



§ Palatine, from ^palatum, the palate : the bones forming the hinder part of the 

 palate of mammals, articulating with the hinder border of the maxilla. 



11 Nasals, (from nasa, the nose), the bones of the nose. 



^ Orbit, from orhis, the socket of the eye. 



** Lachrymal, from laohryma a tear; in mammals this bone carries a duct from 

 the eye to the nose. 



ft Prefrontal ; proe in front of, and frontal, (vide frontal infra.) 



XX Supra-orbital, supra, above and orhis. 



§§ Nares, the nose. 



