326 SHOULDER-GIRDLE IN MONOTREMES, 



digitations from the dorsal surface of the 10th and 11th ribs, the 

 digitations from the 10th rib being about 1 5 cm. from the median 

 line, while that from the 11th rib lies more external. (Fig. 12, 

 Tr. P.) 



Insertion. The spinous portion, which arises by tendon^ 

 soon develops into a sheet of fleshy fibres, and is then joined by 

 the costal portions. The whole muscle now runs forward and 

 slightly outwards, becoming narrower as it approaches the scapula^ 

 where it is inserted by a thin flat tendon on the anterior extremity 

 of the vertebral border of the scapula ; an a[)oneurosis, stretching 

 from the vertebral border of its tendon, also serving to attach it 

 to the vertebral border of the scapula. 



Relations. At its origin from the ribs the muscle is 

 intimately connected with the dermo-dor.si cervicalis band of the 

 panniculus, and the erector spime (sacro-lumbalis), while beneath 

 it lie the costal fibres of origin of the latissimus dorsi. The origin 

 from the spinous proce.sses overlies the greater part of the vertebral 

 origin of the latissimus. As the muscle approaches the scapula 

 it hides from view the costal portions of the serratus magnus, and 

 then overlies in part the teres major and subscapularis, and part 

 of the scapular deltoid. (Fig. 12). 



Innervation. N. accessoriiis, Ornilhorhynchus and EcJildna. 



Westling : same for Echidna. 



Echidna. 



Westling describes this muscle as divided into two portions, 

 an anterior arising from the temporal and parietal bones as well 

 as from a fascia common to it and its fellow of the opposite side ; 

 " inseririt an einem Theile des vertebralen Randes der Scapula, an 

 einem Sehnenstrang langs der Spina Scajjulai (nicht an der Spina 

 selbst), am Acromion und am aiissersten (acromialen) Theile der 

 Clavicula." 



The posterior portion arises by tendon from the dorsal vertebrje 

 and the 10th-l2th rib, and is inserted on to the greater part of 

 thp vertebral border of the scapula. 



