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Show 1000 MESSRS. B. C. A. WINDLE AND F. G. PARSONS ON [Dec. 19, specimens (28, 28 a). It is always difficult to separate the mesialis from the profundus (crureus). Tibialis anticus.-Among the Bradypodidce it is rather difficult to determine the line of demarcation between this muscle and the extensor ballucis, more especially as in both kinds of Sloths the hallux is aborted. In four specimens of Bradypus (1, 4, 5, 6) the muscle rose from the anterior surfaces of the tibia and fibula, and was inserted into the rudimentary first metatarsal bone. In Cholcepus (8, 9, 10) the origin was the same, but the tendou, instead of being inserted into the metatarsal, winds round the ankle to the plantar surface of the foot, and is inserted into the long flexor tendons. In Humphry's specimen (9) and in our own (8) it divided into three slips which joined other three slips from the flexor longus digitorum (tibialis ? fibularis ?), while in Mackintosh's animal (10) it only joined the flexor of the middle toe. Among tbe Myrmecophagidce, the muscle is single in Myrmecophaga (11) and rises from the upper | of the tibia to be inserted into the entocuneiform and slightly into the base of the first metatarsal. In Tamandua (14) there were tibial and fibular origins, and the insertion was into a sesamoid bone on the inner side of the navicular. In Cyclothurus (17, 19, 20, 21) there were tibial and fibular origins, and the insertion in all cases was into the entocuneiform. Among the Dasypodidce, Dasypus (22, 23) has tibial and fibular origins, and an insertion into the entocuneiform, but in Tatusia (25) and Chlamydophorus (27) only the tibial origin was found. In this family the muscle is particularly large. In the Manidce (29, 32, 33) there are tibial and fibular origins, and the insertion is into the entocuneiform and first metatarsal. In the Orycteropodidce (35, 36, 37) it rises from the upper half of the tibia and from the fibula. In Humphry's and Galton's specimens (35, 36) its tendon divides, and is inserted into the first metatarsal and entocuneiform. Extensor proprius hallucis.-In the Bradypodidce we found no separate representative of this muscle in our specimen (1). Humphry (2) and Meckel (4), however, found a small muscle rising from the lower end of the fibula and passing to the rudimentary first metatarsal, a condition also figured by Cuvier aud Laurillard (6). In Cholcepus (8, 9, 10) a similar condition was observed. Among the Myrmecophagidce, Myrmecophaga (11) and Tamandua (14, 15) have the muscle rising from the lower end of the fibula and inserted into (11, 12, 14) the termiual phalanx of the hallux, but in Rapp's specimen (15) it also went to the second toe. In Cyclothurus the extensor proprius hallucis is noticed by both Humphry and Galton ; but the long extensor muscles of the foot were evidently imperfectly differentiated, for Humphry (IV.) found the muscle joining the tendon of the tibialis anticus, whilst in Galton's specimen (20) it united with that of the extensor longus digitorum. In the Dasi/podidce Dasypus (22, 23), Tatusia (25), and Chlamydophorus (27, 28 a), the muscle always rises from the lower part of the fibula and is' |