Wuscles of the Chelonkm ISho alder-girdle. 807 



I think it will be granted, after the comjiarisons already made, that 

 the area of origin for the " omohyoid " in the Chelonian shoulder-gir- 

 dle would find its true position on the coracoid or acromion^ rather 

 than on the scajyula, and considering the origin of the representative 

 of the " supraspinatus " — from both the acromion and the coracoid, — 

 we are not so much puzzled to find where the representative of the 

 former should arise, as we are surprised at the accuracy with which 

 our rule is carried out. 



The muscles which are inserted into the shoulder-girdle cannot l^e 

 homologized so easily, nor should we expect them to agree so 

 closely in difterent types of structui-e, since the attachment of the 

 shoulder-girdle to the body is not by close joints, but by loose mus- 

 cular and ligamentous attachments. Nevertheless a muscle arising 

 from the edge of the cai"a])ace and inserted into the ends of the sca- 

 pula (PI. 13, fig. 2, I'j), and attached by a thin sheet to the side of the 

 same as far as to its base, then continued on to the end of the coracoid 

 (PI. 13, figs. 2 and 5, i-ib), may certainly be considered as a repre- 

 sentative of the "serratus anticus major" and " pectoralis minor," and 

 though presenting slight variations, these are not more than the great 

 modification of the whole arrangement of the shoulder-girdle of the 

 Chelonians would demand. 



The above considerations have suggested a theoretical explanation 

 for the unique relation that the shoulder-girdle l)ears to the general 

 frame-work of the skeleton in the Chelonians, which will, however, 

 be deferred to some future time. 



I have avoided making mention of the interpretations that other 

 authors have given to the muscles under consideration, reserving this 

 matter till the close. In the first place, I had access to oidy one 

 original work on the subject (Riidinger's Muskelen, &c.), and his in- 

 terpretation of homologies did not satisfy me, and I also liad difticulty 

 in making out with certainty how much of the descriptions and deter- 

 minations was original and how much had been taken from other 

 writers. I left them all, therefore, and with scal}»el and pencil under- 

 took to work out the problem for myself. 



Trans. Connecticut Acad., Vol. II. 23 April 1873. 



