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Show 1896.] ANATOMY OF PETROGALE XANTIIOPUS. 697 The Triceps is large and has the human attachments. The Anconeus and Epltrochleo-anconeus are well marked aud normal. The Pronator radii teres has only the condylar head, which is inserted just above the middle of the radius. The Flexor carpi radlalls is normal. The Palmaris longus is large and ends in the palmar fascia, from the inner side of which a muscle rises, ending in tendons for the proximal and distal phalanges of the little finger; this I regard as the abductor minimi digiti. The flexor carpi ulnaris rises from the internal condyle and from the posterior border of the ulna; but there is no distinct head from the olecranon; the absence of this is also noticed by Macalister in the Great Kangaroo and Bennett's Wallaby. The tendon is inserted into the pisiform bone, over which a sesamoid cartilage is situated. The Flexor sublimis digitorum is small, and rises from the surface of the flexor profundus ; it quickly divides into three small muscular bellies, the tendons of which pass to the index, medius, and annularis. The descriptions of Meckel and Macalister agree with this, except that they found tendons to all the fingers. The Flexor profundus digitorum rises from the internal condyle, from the flexor surfaces of the radius and ulna in their upper halves, from the inner side of the ulna, and from the olecranon process. The mass divides into five strong tendons for the thumb and fingers. The Lumbricales are arranged as in Man, except that the one between the annularis and minimus tendons is wanting. This description differs from the one given by Toung'. He describes four lumbricales in Petrogale, one of which is furnished to the thumb. The Pronator quadratus is very thick, and occupies the lower two-thirds of the forearm. The Supinator longus is inserted into the dorsum of the scaphoid. Macalister describes it as being inserted into the first metacarpal in the Wallaby, and into the trapezium and first metacarpal in the Great Kangaroo. Meckel also states that it is present in the Kangaroo. The Extensores carpi radialls longior et brevior were present and normal. Macalister says that they form a single muscle, which is inserted into the 2nd and 3rd metacarpals. I have so often seen this description of these muscles by different authors in various animals, and, on trying to verify it, have always found the two muscles separate, though closely adherent, that I cannot help suspecting that they are normally separate in the Kangaroos. The Extensor communis digitorum is normal, and goes to the four outer fingers. 1 " Intrinsic Muscles of the Mammalian Hand," Journ. Anat. vol. xiv. p. 156. PROC. ZOOL. Soc-1896, No. XLV. 45 |