308 SHOULDER-GIRDLE IN MONOTREMES, 



spinatus. In PI. v. 20, the infraspinatus is rightly named and 

 figured. 



M. SUPRASPINATUS. 



ECHIUXA : M. supraspinatus, all authors. 

 Ornithorhy.sx'hus : AI. siipraspinatus, all authors. 



Echidna. 



Origin. The supraspinatus is a large well developed muscle. 

 It arises from the ventral two-fifths of the inner surface of the 

 scapula and acromion. Its origin is bounded anteriorly by the 

 aci'omio-trachelien ; dorsally by a slight ridge to vvhich the omc- 

 hyoid is attached ; posteriorly by the subscapularis as it winds 

 round the posterior border to encroach on the inner face of the 

 scapula ; the muscle does not, however, arise from the ventral 

 portion of the inner face of the scapula immediately adjoining the 

 coracoid. 



Insertion. Winding round the sharp lower edge of the 

 scapula between the acromion and the glenoid cavity, the muscle 

 then becomes intimately related to the capsular ligament, and 

 continues on posteriorly and somewhat outwards to become 

 inserted by a well marked tendon into that portion of the greater 

 tuberosity immediately contiguous to the articular bead of the 

 bone ; the insertion being placed between the epicoraco-humeral 

 and infraspinatus, and being hidden from view by the clavicular 

 deltoid. (Fig. 4, Ss.). 



Relations. The muscle in running to its insertion becomes 

 closely related on its inner aspect to the epicoraco-humeral, and 

 externally to the infraspinatus. 



Orxithokhynchus. 



Origin. The supraspinatus is a very small muscle arising 

 by fleshy fibres from the internal face of the scapula, from a 

 depression situated close to the sharp ventral border of the scapula 

 that runs between the acromion and the glenoid cavity. 



