OCR Text |
Show 1899.] THE MYOLOGY OF THE EDENTATA. 335 phagidce the arrangement closely resembles that of the Sloths. Of three specimens of Myrmecophaga the muscle was bilaminar in two (12, 13), the superficial part going to the fascia and posterior annular ligament and the deep to the styloid process of the radius. In Tamandua (14, 16) and Cyclothurus (17, 18, 19, 20, 21) the same condition obtained. It is Avell figured by Cuvier and Laurillard (plate 237). In the Dasypodidce the supinator longus is absent in Dasypus (22, 23, 24), Tatusia (25, 26), and Chlamydophorus (27, 28). In the Manidce the muscle may be present (32, 33, 34) or absent (29, 30, 31). When it is present it is closely connected at its origin with the deltoid, so much so that by some observers the two muscles have been described as continuous. In Oryeteropus the muscle is present (35, 36, 37) and rises from a considerable portion of the length of the humerus. It is inserted partly into the radius, partly into the fascia over the tendons. Extensores carpi radiales longior et brevior.-In the Sloths there are usually tAvo insertions, although the muscular belly is described as single. In three specimens of Bradypus (2, 3, 4) the muscle, described as single, ended in two tendons, which Avere inserted into the radial pair of the three metacarpals ; but in our own specimen (i.) the longior was absent and the brevior passed from the external condyle to the middle of the shaft of the central (3rd) metacarpal bone. Mackintosh's specimen (5) appears to have presented an identical arrangement. In three specimens of Cholcepus (8,9, 10), in spite of the presence of only two metacarpal bones, both tendons were present, and in our own (8) Ave noticed that the muscular bellies Avere separable and that the longior Avas the smaller of the two. The two tendons were in all thiee cases inserted into the radial of the two metacarpals. The Myrmecophagidce are remarkable for the suppression of the extensor carpi radialis longior, but the brevior is unusually strong. In Myrmecophaga (11, 12, 13), Tamandua (14, 15), and Cyclothurus (17, 18, 20) only the brevior was present, but in anotber specimen of the latter animal (19) both muscles Avere found. In the Dasypodidce both muscles seem to be usually present, though the two bellies are sometimes described as being fused. The Manidce are remarkable for the absence of the longior, this condition being noticed in five specimens (29, 30, 31, 32, 33). In M. javanica, hoAvever, tendons are described as passing to the second and third metacarpals. In Oryeteropus the longior seems to have been present in (35) and absent in (36). Extensor communis digitorum.-This rises as usual from the external condyle and is inserted into a variable number of digits. In Cholcepus it always passes to the second and third, the only two Avhich are present. In Bradypus it may go to all three digits (1, 5, 6), the two outer (3) or the tAvo inner (4). In Myrmecophaga all the digits may be provided with tendons (12, 13) or only the third and fourth (11). In Tamandua (14, 15) slips go to the medius and annularis only. Cyclothurus (17, 18, 19, 20, 21) possesses only a tendon for the medius. Dasypus (22, 23, 24), |