BY W. J. S. McKAY. 343 



Insertion. The muscle runs posteriorly and outwards, 

 then dorsally to be inserted on the anterior three-fourths of the 

 inner aspect of the vertebi-al border of the scapula. The insertion 

 is placed between the ihomboid externally, and serratus 

 magnus internally ; the tirsl-nanietl muscle hiding the insertion 

 from view. 



Origin, (b) Ventral portion. — This is smaller and is placed 

 at its origin superficial to the portion just described. It arises 

 from the ventral surface of the atlas close to the median line, and 

 from a tendon which stretches between this spot and the transverse 

 process of the axis, and forms an arch from which the muscular 

 fibres spring. 



Insertion. The muscle runs posteriorly and externally to 

 be inserted on the whole of the inner surface of the acromion and 

 ventral third of the spine of the scapula ; also on the dorsal 

 surface of the inner one-fourth of the clavicle ; being placed under 

 cover of the insertion of the anterior part of the ti'apezius. 



Ornithokhynchus. 



Origin. («) Dorsal portion. — This arises by a thin flat 

 tendon from the external border of the distal extremity of the 

 hypapophysis of the atlas. 



Insertion. The muscle runs posteriorly and outwards, 

 becoming much broader and pas.sing superficial to the prevertebral 

 region is inserted on the upper part of the spine and anterior half 

 of the vertebral border of the scapula ; the insertion being placed 

 between the serratus magnus internally, rhomboid posteriorly, and 

 the anterior part of the trapezius antero-externally. 



Origin, [b) Ventral portion. — This is placed superficial to 

 tlie dorsal portion, and arises by a narrow flat tendon from the 

 ventral surface and distal extremity of the hypapophysis of the 

 atlas ; being intimately related with the tendon of the dorsal por- 

 tion, and also with the scalenus which arises from the hypapophysis. 



Insertion. The muscle runs pi'Steriorly and outwards, 

 spreading out like a fan to be inserted on the lower two-thirds of 

 the spine and the immediately adjacent inner surface of the 



