1 34 ELEMENTAR Y ANA TOM Y. [LESS. 



poral bone with a bone termed the post-frontal, and which 

 more or less occupies the place of the post-frontal process of 

 the frontal bone of Mammals. 



A fundamentally different structure may obtain, as in Fishes, 

 where we have, as a rule, no malar ; and where the more con- 

 spicuous representative of the temporal bone (exclusive of 

 the representatives of the petrous portion) is the pre-operculum, 

 which may perhaps be said to replace a zygoma, extending 

 down as it does to the quadrate bone which suspends the 

 lower jaw. The connexion of the quadrate bone, however, 

 with the maxillary bone is only effected by means of soft 

 structures, which must alone, therefore, represent the inferior 

 zygoma of the Sauropsida. The bones which connect the 

 quadrate with the upper jaw have relation not to the zygoma, 

 but to the palate. 



Pf, 



i 97 



FIG. 118. SIDE VIEW OF A BIRD'S SKULL. (After Parker.) 



7, surangular bone of mandible : ar, articular bone ; d, dentary ;f, frontal ; /, 

 malar ; /, lachrymal ; me, median ethmoid ; mx, maxillary bone ; /, parietal ; 

 pf, post-frontal process ; pt, pterygoid bone ; px, pre-maxilla ; g, quadrate 

 bone ; qj, quadrato-jugal ; sg, squamosal; v, vomer. 



Returning to man's own class, we find that the lateral region 

 is generally much more open than in him. The spheno-maxil- 

 lary fissure, for example, is defined by the projection outwards 

 of the alisphenoid. Generally this projection is wanting ; 

 therefore the orbit opens widely into the temporal fossa. 

 This fissure may, however, be more closed up than it is even 

 in man, as we see in certain Apes, and notably in the Howling 

 Monkeys. 



The pterygo-maxillary fissure may also become as it 

 were more or less opened out, and the spheno -maxillary fossa 



