3fusdes of the (Jhelonian Shoulder-girdle. 803 



The muscles "teres minor" and " infraspinatus" (PI. 12, fig, 1,3,4) 

 arise from the more distal or articular half of the " axillary " border, 

 and from the thin lamina of bone connecting this border with the 

 " spine." These two muscles are intimately associated in direction of 

 action, as well as in their points of origin and of insertion, both being 

 inserted on the more dorsal side of the greater (of anthropotomy), or 

 radial tuberosity (PI. 12, fig. 4, r., 4, 3). If these two muscles are rep- 

 resented in the Chelonians, I have little doubt but that the thin sheet 

 of muscle arising from the angle formed by the scapula and acromion 

 (PI. 13, fig. 1, 3, 4), and inserted into the humerus on the dorsal side 

 of the lateral tuberosity (PI. 13, figs. 4 and 7, 3, 4), is the ti'ue one. 



I have called this the nmscidus scapulo-acromiohunieralis, and 

 am strongly inclined to consider it the true representative of the 

 "teres minor" of anthropotomy. The "infraspinatus" may be con- 

 sidered as wanting, or as fused with the " teres minor " — to form this 

 bundle. The assumption is that the lamina of bone connecting the 

 ''axillary border" with the "spine" in the mammalian form of sca- 

 pula is not developed in the Chelonians, and that the element called 

 acromion in the latter is the representative of the ridge called " spine " 

 and the " acromion process " of the former, as will be further explained. 



In the human scapula we observe again a strong muscle arising 

 from the "spine" and acromion process (PI. 12, fig. 1, s), called the 

 deltoid. The area of origin for this muscle is on the edge and sur- 

 face of the S])iiie and acromion, opposite the coracoid process, and 

 reaching from the medial border of the scapula to the end of the acro- 

 mion, where it articulates with the clavicle. It is inserted into the 

 shaft of the humerus, near its middle, on a line with the greater or 

 radial tuberosity (PI. 12, fig. 3, 5). 



The representative of this muscle in the Chelonians arises from the 

 antei'ior side of the acromion ; its area of origin extending from near 

 the scapulo-acromial angle (where it is quite continuous with the mus- 

 ctdus scapido-acrondo-humeralia^ this fact quite agreeing with the 

 idea that this latter muscle is the representative of the " infraspinatus 

 and teres minor,") to near the medial extremity of the acromion (PI. 

 13, fig. 1, 5). 



Its insertion is into the radial tuberosity on its dorsal side (PI. 13, 

 figs. 4 and 7, 5). It will be ol)served that all the luimeral motors in the 

 Chelonians are inserted high up, close about the proximal head of the 

 humerus, to the neck and tuberosities, so that we may not look for 

 exact homologies in regard to their insertional areas. 



The muscle next to be noticed is the " supraspinatus," wdiich arises 

 from the sui'fiice of the scapula beyond the spine, and between it and 

 the coracoid (PI. 12, fig. 1, e). 



