MYOLOGY OF THE ORNITHORHYNCHUS. 139 



VI. PERIN.EAL MUSCLES. 

 Not dissected. 



VII. MUSCLES CONNECTING THE SHOULDER-GIRDLE WITH THE BODY. 



Of the several muscles connecting the scapular arch with the body, 

 the deep portion of the sterno-mastoid, which is really essentially 

 clavicular in its insertion, has been already considered. The omo- 

 hyoid, as usual, forms the direct muscular band between the haemal 

 arches of consecutive cranial vertebrae, in this repeating an ordinary 

 intercostal. The others are in three sets, arising from a, spinous pro- 

 cesses of vertebra? along the median line, b, processes of cervical 

 vertebra? along the side of the neck, and c, from the thorax. Trape- 

 zius is in two parts, one of which is thoracic, while rhomboideus is 

 single ; the cervico-scapular plane, answering to ' levator anguli 

 scapulae,' is double ; besides which, there are, as in ordinary marsupials, 

 two perfectly distinct atlanto-scapular levators. The costo-scapular 

 plane (serratus) is small and slight, and differs from that of some 

 (all?) marsupials in being entirely distinct from levator anguli proper ; 

 there are also other thoracic muscles passing to the shoulder appara- 

 tus. As a whole, the scapular arch is much less mobile than usual, in 

 consequence mainly of the episternal attachment and coraco-sterual 

 articulation. 



Omo-hyoid. As already stated, continuous with the mylo-hyoid, at 

 its hyoid point of insertion ; and there is no division into two bellies 

 by a tendinous intersection, nor any confining of the muscle in its con- 

 tinuity by an aponeurotic pulley. Above it is partly divisible into two 

 fasciculi, the smaller internal one of which is inserted lower down 

 on the hyoid than the other, and is distinct from mylo-hyoid. The 

 muscle forms a single flat ribbon, at first descending nearly straight 

 down the neck, then passing obliquely outward, crossing behind the 

 s.-mastoid,' Jbetween this and levator anguli scapula?, and dipping 

 beneath the episternal bar, to be finally inserted on the scapula, partly 

 fleshy and partly tendinous, just below the acromion, in a notch half 

 way between clavicular and humeral articulations. The ordinary 

 action. 



Trapezius. Large; distinct from deltoid, as in claviculate animals 

 generally, and further resolved into two entirely distinct portions, as 

 if by disappearance from the back between and in advance of the shoul- 

 ders, of the part corresponding to the aponeurotic space of the human 

 subject. The anterior part arises from the occiput (precise limits of 

 origin not visible in the specimen), and thence down the median 

 line of the neck, by an aponeurosis common to it and its fellow, with 

 , only secondary connection with cervical spines, to a point opposite 

 the most prominent part of the scapula, to which the lower border 



