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 squaw o sal. 



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, ^rf' 1 ' 



which supports the fore 



limbs and is itself attached '"'f 



by muscles and ligaments 

 to the vertebral column, 



virtually consists of one yj m*m ^tr 



bone the scapula on 



each side. For in all /;///.>'. 



Mammals except Mono- !^ , , 



tremes, the coracoid, ^ j; m.j 



though a distinct ossifica- rr 



tion, forms only a small 4>: jjp / ^ 



(epicoracoid) process on 

 the anterior margin of the 



glenoid cavity in which .s>/ 



the head of the humerus VJ(| f~"f - 7 ^ 



works. The last of the iw 



metacoracoid is seen in 

 Monotremes. The cla- FlG . 232. Under surface of 



vicle is also much reduced Rabbit's skull. 



in the rabbit, being only ^ Front incisors . ^ small posterior 



about an inch in length incisors; j>mx.> premaxilla; mx., maxilla; 



, i j T P m - 3> ^ird premolar ; m. 3, third molar ; 



and Very Slender. it IS /., jugal;yr., supra-orbital ridge of frontal 



a membrane bone, and lies ^Tg^^^^^ 



in the ligament between tympanic bulla ; b.o., basi-occipital ; 6.s., 



the scapula and the ster- une. sphe 

 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. 



