664 



MAMMALIA. 



vomers beneath, the mesethmoid in the median line, while internally 

 there are several thin scroll-like turbinal bones. 



The lower jaw or mandible consists in adult life of a single bone or 

 ramus on each side, but this is formed around Meckel's cartilage from 

 several centres of ossification. Its condyle works on the squamosal. 



The hyoid lies between the rami of the mandible, in the back of 

 the mouth, and consists of a median " body," and two pairs of horns or 

 cornua extending backwards. 



The Appendicular Skeleton consists of the bones of the 

 limbs and the girdles. 



The pectoral girdle, 

 which supports the fore 

 limbs and is itself attached 

 by muscles and ligaments 

 to the vertebral column, 

 virtually consists of one 

 bone — the scapula — on 

 each side. For in all 

 Mammals except Mono- 

 tremes, the coracoid, 

 though a distinct ossifica- 

 tion, forms only a small 

 (epicoracoid) process on 

 the anterior margin of the 

 glenoid cavity in which 

 the head of the humerus 

 works. The last of the 

 metacoracoid is seen in 

 Monotremes. The cla- 

 vicle is also much reduced 

 in the rabbit, being only 

 about an inch in length 

 and very slender. It is 

 a membrane bone, and lies 

 in the ligament between 

 the scapula and the ster- 

 num. The triangular 

 scapula has a prominent external ridge or spine, continued 

 ventrally into an acromion with a long metacromion pro- 

 cess. The scapula is usually strong, and the clavicle 

 is usually present in mammals which grasp or climb or 

 burrow. 



Under surface of 



Fig. 232. - 

 Rabbit's skull. 



f.i., Front incisors ; p.i.^ small posterior 

 incisors; pvtx.^ prema.\illa; mx., maxilla; 

 pni.^ 3, third premolar ; m. 3, third molar ; 

 7-) jtigal ; /;-., supra-orbital ridge of frontal 

 (on dorsal surface); z.sq., zygomatic pro- 

 cess of squamosal ; Sq., squamosal ; T.b.^ 

 tympanic bulla ; b.o., basi-occipital ; b.s.^ 

 basisphenoid ; //., pterygoid ; //., pala- 

 tine. 



