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Show 1899.] THE MYOLOGY OF THE EDENTATA. 997 internal condyle and the inner head of the gastrocnemius. Myrmecophaga (11, 12) and Tamandua (14, 16), amongst the Myrmecophagidce, have also perfectly distinct representatives of this muscle; and in Cyclothurus (17, 19,20) it is also evidently present. Galton (20) speaks of it as a second head of the semitendinous. In the Dasypodidce, Manidce, and Orycteropodidce the muscle is _ also evidently present, but seems to be rather more closely united with the semimembranosus. Semitendinosus.-The chief point of interest about this muscle is the varying presence of ischial, caudal, or both heads. Iu the Bradypodidce., Bradypus (1, 2, 4, 5, 6) and Cholcepus (8, 9, 10) possess ouly the origin from the tuberosity of the ischium, the insertion being as usual into the upper part of the internal surface of the tibia. In the Myrmecophagidce, our specimen of Mgrmecophaga (11) was especially interesting in that in it the caudal and ischial origins remaiued separate right down to their insertions, aud so formed two distinct muscles. The first of these (semitendinosus anterior) rose from the tuber ischii, and was inserted into the internal tuberosity of the tibia just below the insertion of the semimembranosus.' The second (semitendinosus posterior) rose from the anterior caudal vertebrae, continuing the origin of the caudo-femoralis, and was inserted into the tibia°just below the last. Both these muscles were supplied by the oreat sciatic nerve. In Tamandua (14, 15) only the caudal head^was present. In Cgclothurus (17, 20, 21) the caudal head was alone present, but in another specimen (19) the ischial head was the only one found. Among the Dasgpodidce, Dasypus (22, 23) and Chlamydophorus (27, 28«) had ouly the ischial head, but in Tatusia (25) both ischial and caudal heads were present, A strong prolongation, extending to the heel, from the insertion of the muscle was noticed in Dasypus (22). In the Manidce (29, 32, 33, 34) the caudal head is always present, and in two instances (33' 34) an ischial head was also found, though it was small in the first-mentioned specimen. In the Orycteropodidce (35, 36, 37) the ischial head alone was found, and the same prolongation to the heel already alluded to in Dasypus was noticed. It*will thus be seen that the ischial head is alone present in the Bradypodidce and Orycteropodidce ; it is also always present in the Dasypodidce, though occasionally accompanied by a caudal head. In the Manidce the caudal head is always found, aud the ischial, if present, is subsidiary ; while in the Myrmecophagidce either ischia] or caudal, or both heads may appear. The presence of a tendinous intersection in the muscular belly of the semitendinosus has evidently been sought for by many of the dissectors of these animals, but so far we have only found its presence recorded in one specimen of Chlamydophorus (27) described by Macalister. Flexor cruris lateralis (Biceps femoris).-Among the Bradypodidce, Bradypus (1, 2, 4, 5) and Cholcepus (8, 9, 10) have the muscle rising from the tuberosity of the ischium, but not from the caudal vertebrae. The insertion is usually into the fascia of the |
