150 HIGH SCHOOL ZOOLOGY. 



rest of its course it tnay be ligamentous, or formed into cerato- 

 and epi-liyal l)ony pieces. The posterior cornua are formed by 

 one bony piece on each side, which on account of their support- 

 ing the larynx receive the name of thyro-hyal. 



7. Considerable difference will be observed in the structure 

 of the shoulder-gii'dle, and the mode of its attachment to the 

 trunk. In the Sauropsida wo saw that an intimate connection 

 of the skeleton of tho anterior limb to tho trunk was secured by 

 the union of the clavicles and coracoids to the sternum. But 

 in the Mammals both these bones may be absent or very much 

 iv'duced in size, the shoulder-girdle being repi'esented only by the 

 scapula, which is then connected to the trunk by muscles alone. 

 In the cat e.g., the coracoid is in the form of a mere process 

 projecting from the scapula in the neighborhood of the glenoid 

 cavity, and the clavicle, which iia man is connected to the spine of 

 the sca})ulaand the manubrium of the sternum, is rudimentary. 

 As regards the rest of the appendicular skoloton little need be 

 said, except to call attention to the comparatively primitive 

 arrangement of the parts (with the exception of the position of 

 the radius), to the incipient or complete absence of the first toe, 

 the greater development of one element in the carpus and tar 

 sus for the attachment of muscles, and the fact that the meta- 

 carpals and metatai-sals (metapodials) are not in contact with 

 the gi'ound in locomotion. 



In regard to the fii-st point it will be observed that the radius, 

 although related to the inner border of the car[)us and hand, is 

 connected with the outer border of the humerus ; this is attribute 

 aVjle to a twist in the lower end of that bone, which changes 

 the position of the radius at the elbow joint, and I'endere it 

 necessary that it should cross the ulna so as to reach the inner 

 border of the hand. 



In many membei's of the cat's own order, so-called 2)lantigrade 

 Carnivores, the feet have a larger surface of contact with the 



