Lect. II.] 



HINGING OF THE LOWER JAW. 



39 



shows how this is done, and why the feat of fly-catching 

 is so difiicult in the dog trying to sleep in the sun, l^ut 

 kept awake by teasing flies. 



In the Diickhill, as in mammals generally, the pier 

 or hinge-piece is gone, and the maxilla inferior (or 



cr '0J> rj ^^^ 



Fis. 4. 



Fig. 4. — Skull of Common Fowl {Gallus domesticus) one-half larger than specimen. 

 px, preraaxillary ; mx, maxillary; v, vomer; ?i, nasal; eth, ethmoid; I, lacrymal; 

 pe, perpendicular ethmoid ; ^w, presphenoid ; I, olfactory nerve ; io.s, interorbital 

 space ; os, orbitosphenoid ; /, frontal ; pf, post-frontal ; p, parietal ; sq, squamosal ; 

 s.o, superoccipital ; j.}), jugal process of squamosal ; eo, exocciptal, V, 5th nerve ; 

 II, oj)tic nerve ; ty.c, tymimnic cavity ; 6;!, basi-temporal ; q, quadrate ; 2^U> ptery- 

 goid ; pa, palatum ; j, jugal ; qj, quadrate-jugal ; p.ap, posterior angular process ; 

 iap, internal angular process ; ar, articular ; ag, angular ; sa.g, supra-angular ; 

 d, dentary. 



Fig. 4a. — Auditory Columella of Fowl, magnified 6 diameters, and shown from the 

 inside and end. 



mandiljle) is hinged directly to the temporal bone, a solid 

 part of the strong skull-wall. What has become of the 

 " OS quadratum," as the bird's jaw-pier is called ? The 

 answer is, that in the mammal there takes place a 



'f/p+® 



