SKELETON IN MAMMALIA. UPPER ARM AND FORE- ARM. 499 



In the INSECTIVORA the shoulder girdle is well developed 

 and, as in Rodents, remains are met with of various parts not 

 generally seen in mammals. In the Shrews the scapula is 

 long and narrow, and has a well-marked spine, whose end 

 bifurcates, forming the acromion and metacromion. The 

 clavicle is long and slender, and is connected with the sternum 

 and acromion by vestiges of the precoracoid. Considerable 

 remains of the sternal end of the coracoid are also found. In 

 Potamogale, however, there are no clavicles. In the Mole the 

 shoulder girdle is greatly developed, and of very remarkable 

 form. The scapula is high and very narrow, with the spine 

 and acromion very little developed. The other shoulder girdle 

 element is an irregular bone, which articulates with the 

 humerus and presternum, and is connected by ligaments with 

 the scapula. This bone appears to represent both the coracoid 

 and the clavicle, being formed partly of cartilage bone, partly 

 of membrane bone. 



In the CHIROPTERA the scapula is large and oval, and has 

 a moderately high spine and a large acromion. The coracoid 

 process is well developed and is often forked. The clavicles are 

 also well developed, and vestiges of the precoracoid and of the 

 sternal end of the coracoid are often found. 



In PRIMATES the clavicle and coracoid process are always 

 well developed. In Man and the Gorilla the scapula has a 

 long straight suprascapular border, a well-developed coracoid 

 process and spine, and a large curved acromion. Vestiges of 

 the precoracoid occur at each end of the clavicle. The shape 

 of the scapula varies much iri the lower Primates. 



THE UPPER ARM AND FORE-ARM. 



In the MONOTREMATA the humerus is short, very broad at 

 each end and contracted in the middle. The radius and ulna 

 are stout and of nearly equal size, while the ulna has a greatly 

 expanded olecranon. 



In the MARSUPIALIA the humerus is generally a strong bone, 



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