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Show 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 Borso-epitrochlearis is small, and does not quite reach the olecranon. The Rhomboid muscles are in one continuous layer; they rise from the ligamentum nuchse 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 scapulae 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 ; (fi) rises from the 2nd aud 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; (o) is the pectoralis quartus, and comes from the linea alba to be inserted with the ventral panniculus just below y. Possibly (8 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 Beltoid has the three constituent parts-clavicular, acromial, and spinous-fused as in M a n ; 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 Bennett's Wallaby. In the Great Kangaroo the two muscles are equal, according to Macalister. The Teres minor is easily separable 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 rujicollis. 1 Op. cit. |