324 SHOULDER-GIRDLE IN MONOTREMES, 



Echidna. 



Origin, (a) Anterior division. — This part of the trapezius 

 arises by a thin aponeurotic tendon, attached to a well-marked 

 curved depression (linea temporalis) on the parietal bone ; slightly 

 from the occipital bone in the mid-line, and also from a tendinous 

 raphe, in the mid-dorsal line, common to it and its fellow of the 

 opposite side. (Fig. 10, Tr. A.) 



Insertion. The muscle runs outwards, posterior and down- 

 wards, to be inserted, (a) on the anterior one-third of the vertebral 

 border of the scapula ; (b) on the inner border of the acromion ; 

 (c) on the outer third of the clavicle. The muscle is not inserted 

 on to the spine of the scapula, though it is attached to it by fascia. 



Relations. At its origin the tendon of the muscle is but a 

 thin sheet, but as the muscle runs outwards it becomes thick and 

 fleshy, and at its insertion tendinous fibres are but little seen 

 except in the I'egion of the acromion. The dermo-dorsi cervicalis 

 and the dermo-brachio-cephalic bands of the panniculus lie super- 

 ficial to the muscle at its origin. When the trapezius is reflected 

 it is seen that as we approach the ventral border of the muscle 

 (which lies superficial to the sterno-mastoid), cleavage takes place 

 in a plane parallel to the surface from within outwards, so that a 

 superficial and a deep layer are formed, and the ventral border of 

 the rhomboid lies between these two layers. 



The muscle lies superficial to the rhomboid. On approaching 

 its insertion it covers the insertion of both portions of the acromio- 

 trachelien, and becomes related to the insertion of the posterior 

 portion of the trapezius, scapular origin of the clavicular deltoid, 

 the origin of the infraspinatus, and the outer origin of the acromio- 

 clavicular part of the deltoid. 



Origin. Posterior jiortioii of the trapezius. — This arises from 

 tlie spine of the sixth dorsal vertebra, and from the dorsal spines 

 posterior to this to about the 13th, the exact number being 

 indefinite inasmuch as the aponeurosis of the trapezius merges 

 posteriorly into the general dorso-lumbar aponeurosis. The muscle 

 also arises by four distinct slips from the 9th to the 12th rib 

 inclusive. (Figs. 10 et 11, Tr. P.) 



