288 SHOULDER-GIRDLE IN MONOTREMES. 



Insertion. The muscle runs outwards and posterior, 

 narrowing as it approaches its insertion on a groove on the ventral 

 surface of the greater tuberosity, and on the outer half of the 

 ridge which runs from the greater to the lesser tuberosity on the 

 antero-internal face of the humerus (and bounds the concavity 

 [bicipital groove] between the two tuberosities). 



Relations. At its origin the muscle on the left side is 

 partially hidden by the interclavicle, while on the right side in 

 addition it is hidden by the left epicoracoid. On the ventral 

 surface of the tuberosity the tendon of insertion is placed external 

 to the insertion of the supraspinatus and internal to that of the 

 P. major, being partially hidden by the P. major and clavicular- 

 deltoid ; while the rest of the insertion is fleshy and is intimately 

 related to the coraco-brachialis brevis. 



Ornithorhynchus. (Fig. 7, Ep. H.). 



Origin. The muscle arises from the ventral surface of the 

 epicoracoid, a small space excepted, as in the Echidna, for the 

 biceps origin. 



Insertion. The muscle arising by fleshy fibres runs pos- 

 terior and outwards over the ventral aspect of the capsular 

 ligament of the shoulder joint, and becoming narrower as it 

 approaches its insertion by fleshy fibres on the posterior face of 

 the humerus, just internal to the insertions of the P. major and 

 clavicular-deltoid, and by tendon on the ventral surface of the 

 greater tuberosity ; the insertion being between that of the 

 P. major externally and of the supraspinatus and infraspinatus 

 internally. 



Relations. The mu.scle at its origin is partially hidden 

 from view by the median and transverse portions of the inter- 

 clavicle. The muscle on the left side is also overlapped and hidden 

 by the right epicoracoid (this being the opposite condition to that in 

 Echidna). As it runs to its insertion it has the epicoracoid head 

 of the biceps closely connected with its postero-internal border, 

 while it hides the insertions of the supra- and infraspinatus. 



