306 Muscles of the Ghelonian Shoulder-girdle. 



This closes tlie list of muscles arising from the scapula and its pro- 

 cesses in man, and acting upon the arm. 



There is some reason for believing the episternal plates to be the 

 representatives of the " clavicles " of anthropotomy. A portion of the 

 representatives of the deltoid arises from the above mentioned ele- 

 ments. The acromion is attached to it ligamentously. The repre- 

 sentative of the "sterno-cleido-mastoid" does not arise from it in any 

 cases I have observed, but generally only from the medial edges of 

 the " hyosternal plates," when they meet, or from the middle of the 

 cartilaginous part of the sternum, when these plates do not meet at 

 the medial line. 



If w^e are to presume that the Chelonians have a representative of 

 the mammalian clavicle, I think the episternal plate presents more 

 characters homological with those of the clavicle than does any other 

 element of the skeleton. 



The anterior horizontal element of the shoulder-girdle, it will be 

 remembered, is, in this pa})er, considered to be the representative of 

 the s[)ine and acromion process of the mammalian scapula, and not 

 the clavicle, as Rtidinger and some others regard it. 



Parker, in his work on the Shoulder-girdle and Sternum, regards 

 the ej^isternal element of the })lastron as the repiiesentative of the 

 clavicle. (See Parker's Mongr. on Shoulder-girdle and Sternum, 

 1868, pp. 133, &c.) 



In the Chelonians there are no muscles, now remaining to be consid- 

 ered, which arise from the shoulder-girdle proper and act upon the parts 

 of the fore-limb. In the genus Ghelonia a few special bundles were 

 obsei-ved arising from the base of the scapula and acting upon the 

 humerus ; but they must be regarded as " special muscles," as they 

 were observed in no other specimens dissected. 



In the Chelonians a long muscle arises from the anterior edge of 

 the coracoid (PI. 13, figs. 1, 5, lo), and runs forward imder the neck to 

 the hyoid apparatus. * 



It arises in man from the "superior" (coracoidal) border, at the 

 base of the coracoid process (PI. 12, fig. 1, lo), and is inserted into 

 the hyoid apparatus. The relations which the areas of origin for this 

 muscle, the " supraspinatus " and the " coraco-brachialis," bear to 

 each other, is too closely followed in the Chelonians to be passed over 

 as of no importance. 



The areas of attachment of the muscles thus help in the determina- 

 tion of the bones, while they furnish the means, probal)ly the most 

 accurate, for determining the muscles themselves in the study of com- 

 parative anatomy. 



