644 



MAMMALIA. 



Associated with the olfactory chambers are the nasals above, the 

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

 there are several thin scroll-like turbinal bones. As special characters 

 of the skull should be noted the incomplete ossification of certain of the 

 bones, e.g. of the maxilla, and the development of slender rod-like 

 processes from some of them, e.g. the squamosal, which help to keep the 

 parts of the skull firmly connected. 



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 ex- 

 tending 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 at- 

 tached by muscles and 

 ligaments to the verte- 

 bral column, virtually 

 consists of one bone — 

 the scapula — on each 

 side. For in all Mam- 

 mals, except Mono- 

 tremes, the coracoid, 

 though a distinct ossifi- 

 cation, forms only a small 

 (epicoracoid) process 

 overhanging the edge of the glenoid cavity in which the head 

 of the humerus works. The last of a distinct metacoracoid 

 is seen in Monotremes, though it may be sometimes re- 

 presented by a small independent ossification on the ventral 

 surface of the glenoid cavity. The clavicle 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 sternum. The 

 triangular scapula has a prominent external ridge or spine, 

 continued ventrally into an acromion with a long meta- 



Fig. 280. — Rabbit's fore-leg. 

 Sc, Scapula ; cor., coracoid process ; ac, 

 acromion; H., humerus; A'., radius; I/., 

 ulna; C. carpal region; M.C., metacarpal 

 region. 



