THE SKELETON IN MAMMALIA. SHOULDER GIRDLE. 497 



SUBUNGULA.TA. Typotherium (Toxodontia) differs from all 

 other known Ungulates in having well-developed clavicles ; 

 its scapula has a strong backwardly-projecting process, much 

 like that in Rhinoceros. 



Phenacodus (Condylarthra), has a curiously rounded 

 scapula, with the coracoid and suprascapular borders passing 

 imperceptibly into one another. The scapula resembles that 

 of a carnivore more than does that of any existing Ungulate. 



Procavia has a triangular scapula with a prominent spine 

 and no acromion ; there is a large unossified suprascapular 

 region. 



The scapula in the Proboscidea has a large rounded supra- 

 scapular border and a narrow, slightly concave glenoid border. 

 The spine is large, and has a prominent process projecting 

 backwards from about its middle. The spine lies towards 

 the front end of the scapula, so that the postscapular fossa is 

 much larger than the prescapular fossa. 



In RODENTIA the shoulder girdle is of a rather primitive 

 type. The scapula is generally high and narrow, somewhat 

 as in Ruminantia; it differs, however, from the Ruminant 

 scapula in having a high acromion, which is often, as in the 

 Hares and Rabbits, terminated by a long metacromion. The 

 development of the clavicle varies, and sometimes it is alto- 

 gether absent. It is frequently connected by cartilaginous 

 bands or ligaments (fig. 104, 7 and 9), on the one hand with 

 the scapula, and on the other with the sternum. These un- 

 ossified bands are remains of the precoracoid. Epicoracoidal 

 vestiges of the sternal ends of the coracoids (fig. 104, 11) are 

 also often present. 



In the CARNIVORA VERA the scapula is large, and generally 

 has rather rounded borders. The spine and acromion are well 

 developed, and the prescapular and postscapular fossae are 

 nearly equal in size. The coracoid is very small, and the 

 clavicle is never completely developed, being often absent, as 

 in the Bears and most of their allies. In the Seals (Phocidae) 

 R. 32 



