1867.] 



MYOLOGY OF IGUANA TUBERCULATA. 



781 



from the tendon of the latissimus dorsi. Is this head the homologue 

 of the dorso-epitrochlear, which sometimes, as in Ilyrax*, takes 

 origin from the scapular arch, but normally springs from the tendon 

 of the latissimus dorsi? 



(3) The third, or external humeral head, arises from the whole 

 outer surface of the humerus below the head of the bone, extending 

 as it does above the insertions of the deltoid and infraspinatus 

 (figs. 1, 2, 8 & 10, r. 3). 



(4) The last, or internal humeral head (figs. 6, 9 & 10, T. 4), 

 similarly arises from the internal surface of the humerus to the head 

 of the bone. At its summit this part of the muscle has contiguous 

 to it, antero-internally, the short part of the coraco-brachialis and 

 the insertion of the subscapularis, while the tendons of the latissi- 

 mus dorsi and infraspinatus are contiguous to it on its postero- 

 external side (fig. 9). 



Fig. 9. 



Muscles of inside of I'iglit arm, the scapular arch being detached, and the 

 costo-coracoid muscle (6'. C.) being cut short and reflected. 



B. Biceps muscle. C. Sternal margin of coracoid bone. C/?. 1. First, or short, 

 part of coraco-brachialis muscle. C. B. 2. Second, or long, part of coraco- 

 brachialis. C. C. Costo-coracoid. F. B. Flexor carpi radialis. F. U. 

 Flexor carpi ulnaris. L. B. Latissimus dorsi. S. 2. Second part of sub- 

 scapularis. T.\. First, or external long, head of triceps. T.'2. Second, or 

 internal long, head of triceps. T. 4. Fourth, or internal hiuueral, head of 

 triceps, t. Tendon fi-om latissimus dorsi to triceps. 



All these four portions are united together at above the middle of 

 the arm, and are together inserted into the proximal end of the ulna 

 and into the patella-like sesamoid immediately above it. 

 Coraco-brachialis . This muscle consists of two parts : — 

 (1.) The first of these, or shorter portion, is a broad muscle, and 

 much resembles the short coraco-brachialis of the Echidna-^'. It 

 arises, by muscular fibres, from the whole outer surface of the cora- 

 coid, from the lower spur of the epicoracoid, and from the membrane 



* Proc. Zool. Soc. 1866, p. 340, fig. 5, D. c. 

 t Trans. Linn. Soc. vol. xxv. p. 385. 



