1870. | MYOLOGY OF CHAM4LEON PARSONII. 867 

Deepest muscles of extensor surface of right forearm. 
M. P. Extensor metacarpi pollicis. P.A. Pronator accessorius. P. Q. Pronator 
quadratus. SS. Z. Supinator longus. 
1. The first part (fig. 13, 7") arises from the axillary margin of. 
the scapula, just behind (when the humerus is horizontal, above) the 
glenoid surface. This answers to both of the first two parts (exter- 
nal and internal long heads) of the triceps of the Iguana; and a 
strong tendon on its inner surface indicates the part answering to 
the internal long head of that muscle in the last-named animal. 
2. The second part arises from the whole posterior surface of the 
humerus and part of its outer and inner surfaces. Its origin extends 
upward (the humerus being placed vertically) to just below the head 
of the bone, and above the insertion of the second part of the deltoid. 
Inwardly it extends to just behind the insertion of the latissimus 
dorsi. Externally (fig. 13, 7”) it reaches the posterior border of the 
brachialis anticus. 
3, The third part (fig. 8, 7’. Z) is much the smallest, and is closely 
connected with the second part. It springs from the inside of the 
humerus, its origin rising to the level of the upper limit of the inser- 
tion of the latissimus dorsi. 
These three parts unite together, and are inserted in common into 
the proximal end of the ulna, a large sesamoid ossicle being situated, 
behind the elbow, in the tendon of insertion. 
The biceps (figs. 1, 8, 9, 10, 11, 13, 15, & 16, B) has a single ori- 
gin, by a long and strong tendon, from the coracoid, just external to 
its sternal groove. This tendon is at first covered by fibres of the 
subclavius, and then passes over the short coraco-brachialis. De- 
scending in front of the insertion of the pectoralis, it there becomes 
fleshy, and becomes more or less divisible into two bellies, which em- 
brace the brachialis anticus in front, but leave part of the latter vi- 
sible within and without the arm. _It ends in two tendons, one for 
each belly (fig. 16, B), which, by their divergence, expose the bra- 
chialis anticus in the middle of the lower part of the upper arm. One 
of these tendons is inserted into the ulnar side of the front aspect of 
the radius, at the place of the tubercle; the other is inserted into 
the ulna, in front of its articular surface for the humerus. 
