296 SHOULDER-GIRDLE IN MONOTREMES, 



from about one-third of the proximal portion of the upper surface 

 of the coraco-brachialis longus. (Fig. 4, Be. ii.). 



Insertion. The two portions of the biceps run out in com- 

 pany, coursing over a large bare surface on the antero-internal 

 face of the humerus. The epicoracoid belly then develops a well- 

 marked tendon, and becoming hidden by the coracoid belly it i uns 

 outwards, and twining round the humerus it is inserted on the 

 middle third of the ulna. The coracoid portion on approaching 

 the forearm also develops a strong tendon which is inserted on 

 the radius distal to the insertion of the smaller belly on the ulna. 



Relations. The epicoracoid portion at its origin is in con- 

 tact with the epicoraco-humeral ; it then passes superficial to the 

 rectus tendon (inserted on the coracoid). The two parts together 

 hide the coraco-brachialis brevis, and as they wind round the 

 humerus they come into relation with the tendon of insertion of 

 the clavicular deltoid. 



Orxithorhynchus. 



Origin, (a) Epicoracoid head arises from a small area on 

 the postero-internal portion of the ventral surface of the epicora- 

 coid. Running outwaixls and posterior over the insertion of the 

 rectus, the muscle passes across the coraco-brachialis brevis, and 

 comes into contact with the anterior border of the coracoid belly, 

 and passing round the humerus, distal to the insertion of the deep 

 panniculus, it develops a tendon which soon after fuses with the 

 tendon of the coracoid portion. (Figs. 7, 9, Be. i.). 



(b) Coracoid head arises by an attenuated tendon (common to 

 it and the coraco-brachialis longus) from the external border of 

 the distal extremity of the coracoid. Running outwards a thick 

 rounded muscular belly develops closely adherent to the ventral 

 surface of the coraco-brachialis longus beneath. (Figs. 7, 9, Be. ii.) 



Insertion. Winding round the humerus the coracoid belly 

 now develops a tendon, and becoming fused with the epicoracoid 

 portion, the conjoined tendon now comes to lie between the radius 

 and ulna, and is inserted on the middle third of the latter bone. 



