1867.] MYOLOGY OF IGUANA TUBERCULATA. 777 



Fis:. 7. 



•SJtfy ^ 



Muscles of the inside of the right half of the scapular arch. 



V. C. Costo-coracoid. D. 1. First part of deltoid, curving over anterior (upper) 

 margin of coracoid. E. S. C. External sterno-coracoid. /. S. C. Internal 

 sterno-coracoid. /.' Intercostal. L. C. Levator claviculae. 0. H. Omo- 

 hyoid. S. 1. First part of subscapularis. S. 2. Second part of subscapu- 

 laris. S. C. M. Sterno-cleido-mastoid. S. Mg. \-S. Mg. 4. Four parts of 

 serratus magnus. 



(2) The second and smallest portion (and which some might 

 take to represent the rhomboideus) arises from the last but one cer- 

 vical rib, but considerably higher up than the first portion of the 

 serratus magnus. It is inserted (fig. 7, S. Mg. 2) into the inner sur- 

 face of the posterior (inferior) vertebral angle of the scapula. 



(3) The third portion arises from the outside of the ribs of the 

 sixth and seventh cervical vertebrae. It is inserted (fig. 7, S. Mg. 3) 

 along the inside of the cartilaginous summit of the scapula, not far 

 from its vertebral margin, and extending along the greater part of 

 the extent of that margin. This portion is double at its origin, each 

 rib giving rise to its own layer of muscle ; but the two have a com- 

 mon insertion. 



(4) The fourth part of the serratus magnus springs from the out- 

 side of the seventh cervical rib, below the origin of the third portion 

 of the serratus. It is inserted (fig. 7, S. Mg. 4) into the inner side 

 of the cartilaginous part of the scapula close to the anterior (supe- 

 rior) vertebral, angle, between the most anterior parts of the origin 

 of the subscapularis and of the insertion of the third portion of the 

 serratus. 



Deltoid (figs. 1, 2, 7 & 8, Z>. 1 and D. 2). This muscle is very 

 large, and, in the specimen examined by me*, is easily separable 

 into two parts, which, however, have a common insertion : — 



(1) The lower portion consists also of two layers, superimposed 

 one on the other, — the superficial layer arising from about the lower 

 (or sternal) half of the posterior part of the deep surface of the cla- 

 vicle, and from a similar extent of the hinder border of that bone, 

 posterior to the attachments of the trapezius, omo-hyoid, and sterno- 

 * This was not the case in Meckel's specimen (Joe, cif. p. 340). 



Proc. Zool. Soc— 1867, No. L. 



