1896.] ANATOMY OF PETROGALE XANTHOPUS., 695 
thoracic spines, and from the 9th, 10th, and 11th ribs. The most 
anterior fibres are connected with those of the trapezius over the 
infraspinatus, becoming gradually lost in the aponeurosis; the 
more posterior fibres wrap round the teres major, as in Man, to be 
inserted into the humerus. 
The Dorso-epttrochlearis is small, and does not quite reach the 
olecranon. 
The Ehomboid muscles are in one continuous layer; they rise 
from the ligamentum nuchz close to the skull, as far back as the 
3rd thoracic spine. They are inserted as in Man. Macalister ! 
describes a rhomboideus capitis in the Great Kangaroo, as well as 
in Bennett’s Wallaby. 
The Levator anguli scapule and Serratus magnus are, as usual, in 
one layer, which rises from all the cervical transverse processes 
and from the anterior seven ribs. The slip which rises from the 
transverse process of the atlas is inserted into the inner third 
of the spine of the scapula; the rest of the muscle goes to the 
vertebral border of that bone. 
The Pectoral mass is divided into four distinct parts: (a) the 
superficial part rises from the whole length of the sternum and 
from the inner part of the clavicle, it is inserted into the middle 
of the humerus with the deltoid ; (/3) rises from the 2nd and 3rd 
costal cartilages, and is inserted into the upper part of the 
pectoral ridge; (y) comes from the first cartilage, and is inserted 
just above the last, it is supplied entirely by the internal anterior 
thoracic nerve; (6) is the pectoralis quartus, and comes from 
the linea alba to be inserted with the ventral panniculus just 
below y. 
Possibly 3 and y correspond to the human pectoralis minor. 
The Subclavius is large, has the usual origin, and is inserted 
into the whole length of the posterior border of the clavicle. 
The Deltoid has the three constituent parts—clavicular, acromial, 
and spinous—fused as in Man; the insertion is into the humerus 
above the middle. The circumflex nerve supplies the whole of 
the muscle. 
The Supraspinatus is smaller than the infraspinatus, as in 
Benneti’s Wallaby. In the Great Kangaroo the two muscles are 
equal, according to Macalister. 
The Yeres minor is easily separable from the infraspinatus, as it 
is in the Wallaby, but not in the Great Kangaroo. 
The Yeres major is normal ; its lower border is wrapped round 
by the latissimus dorsi tendon. ; 
The Coraco-brachialis, as in all the Kangaroos, consists solely of 
the rotator humeri. Meckel says that the muscle is entirely 
absent in these animals, but the rotator humeri, if not specially 
looked for, is very easily missed. According to Macalister the 
rotator humeri is divided into two slips in Macropus rujicollis. 
1 Op. cit. 
