1896.] ANATOMY OF PETBOOALB XANTHOPUS. 095 



thoracic spines, and from the 9th, 10th, and 11th ribs. The most 

 anterior fibres are connected with those o£ the trapezius o\'er 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-epiirochlearis is small, and does not quite reach the 

 olecranon. 



The Rhomboid muscles are in one continuous layer ; they rise 

 from the ligaraentum nuchse close to the skull, as far back as the 

 3rd thoracic spine. They are inserted as in Man. Mncalister ' 

 describes a rhomboideus capitis in the Great Kangaroo, as well as 

 in Bennett's Wallaby. 



The Levator anguli scapulm 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 wliole 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 ; {I) 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. 



Ihe Suhclavius is large, has the usual origin, and is inserted 

 into the whole length of the posterior border of the clavicle. 



The Deltoid lias 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 Suprasjnnatus is smaller than the infraspinatus, as in 

 Bennett's Wallaby. In the Great Kangaroo the two muscles are 

 equal, according to Macalister. 



The Teres minor is easily sei)arable from the infraspinatus, as it 

 is in the Wallaby, but not in the Great Kangaroo. 



The Teres 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 rujkollis. 



^Op. cit. .. 



