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Show 1899.] THE MYOLOGY OF THE EDENTATA. 1005 radial ossicle, or so-called pre-pollex. In Tamandua (14, 15) the muscle is absent. Among the Dasypodidce the plantaris rises from the ridge above the external condyle in Dasypus (22, 23), and is continued into the sole of the foot, where it flattens out and sends slips to three or four of the digits, which slips are perforated by the tendons of the flexor longus digitorum. In Tatusia (25) there is no separate plantaris. In Chlamydophorus (27, 28, 28 a) the tendon passes into the sole of the foot, where it divides into four slips. In the Manidce (29, 32, 33, 34) there is no separate plantaris, it is probably fused with the very large external head of the gastrocnemius. In the Orycteropodidce (35, 36, 37) the generalized mammalian arrangement is found ; the plantaris passes under the tuberosity of the calcaneum, and forms a fibrous flexor brevis digitorum for the four outer digits. Flexor brevis digitorum.-In the Bradypodidce (1, 2, 5, 9, 10), Myrmecophagidce (11, 14, 15, 17), and Manidce (29, 32), the muscle rises from the posterior part of the lower surface of the calcaneum, and has no connection with the plantaris when that muscle is present. The insertion is into the three middle or four outer digits. The tendons are usually inserted into those of the flexor longus, instead of being perforated by the latter. The information, however, as to the manner of ending of these tendons is very scanty. In the Dasypodidce (22, 23, 27, 28) and Orycteropodidce (35, 38, 37) the flexor brevis is a continuation of the plantaris, as in most generalized mammals. Flexores tibialis et fibularis.-In the Bradypodidce these two muscles are difficult to distinguish : in any case they coalesce before reaching the ankle, and then divide into three tendons, which pass to the second, third, and fourth toes respectively. This applies to Bradypus (1, 2, 5) and Cholcepus (8, 9, 10). In some records of Bradypus (2, 5) a femoral head is also recorded, but a consideration of the conditions has decided us to regard this as a plantaris. Among the Myrmecophagidce the two muscles are practically inseparable ; they form a single flat tendon, which in Myrmecophaga (12) and Tamandua (15) has a sesamoid body where it passes into the sole of the foot. In Tamandua (14, 15) tendons pass to all five toes, but in Cyclothurus (17, 19, 20) there is no slip for the hallux. In the Dasypodidce (22, 23, 25) the tibial and fibular heads unite in the lower part of the leg and are inserted into a very large sesamoid bone in the sole of the foot, which is held in place by a fibrous band from the calcaneum, the equivalent of the accessorius. From the front of the sesamoid bone five tendons pass to the terminal phalanges of the five digits. In Chlamydophorus (27) the sesamoid bone was replaced by a cartilaginous nodule. In the Manidce (22, 23, 25) the two muscles are much more distinct, the fiexor fibularis forming a very large tendon into the inner side of which the small tendon of the flexor tibialis is inserted. There are tendons for the four outer toes, but none for the hallux. In the Orycterojjodidce (35, 36) the flexores tibialis et fibularis fuse in the leg and from the tendon PROC. ZOOL. Soc-1899, No. LXV. 65 |