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Show 336 MESSRS. B. C A. WINDLE AND F. G. PARSONS ON [Mar. 7, Tatusia (25, 26), and Chlamydophorus (27) have tendons for the index, medius, and annularis. In the Manidce a strong tendon passes to the medius, and the annularis and minimus are provided with feeble slips (29, 30, 31, 32, 33, 34). In the Orycteropodidce (35, 36, 37) all four digits are provided with tendons. Extensor minimi digiti.-In the Sloths this muscle is often either replaced by or becomes an extensor brevis digitorum, which rises from the dorsum of the carpus and metacarpus and is inserted into one or more of the few* digits. It existed under this condition in tAvo specimens of Bradypus (2, 3) out of five examined, and in one specimen of Cholcepus (9) out of three. In the cases in which an extensor brevis was not present, it Avas replaced by a normal extensor minimi digiti, which obtained an insertion into tbe most ulnar digit. In Myrmecophaga (11, 12) the muscle in question only Avent to the fifth digit. In Tamandua (14) it was attached to the fourth and fifth digits, and in Cyclothurus (19, 20) to the rudiments of the same. Dasypus (22, 23) and Ghlamydopjhorus (27) had this muscle attached to the fourth and fifth digits, and Tatusia to the fifth only. In the Manidce (29, 30, 32, 33) the muscle was present, but in our specimen it Avas inserted into the fifth metacarpal bone instead of into the phalanges. As a double tendon from the extensor communis to minimus is described in (32), it is probable that the condition was the same as has just been mentioned. In Oryeteropus the extensor minimi digiti is inserted into the minimus and annularis (35, 37) or into the minimus alone (36). Extensor carpi ulnaris.-There is little variety about this muscle ; it is always present and rises from the external condyle and dorsal border of the ulna and is inserted into the base of the most ulnar of the metacarpals present. Extensor ossis metacarpi pollicis.-In the Bradypodidce both Bradypus (1, 2, 3) and Cholcepus (8, 9, 10) have this muscle inserted into the trapezium, though in Mackintosh's specimen (5) the insertion is said to have been into the base of the inner metacarpal. In the Myrmecophagidce the muscle appears to be always present, but in Cyclothurus (17, 18) it is said to rise from the external condyle. In the Dasypodidce it is present and extends from the ulna to the first metacarpal. In the Manidce it sometimes is inserted into the first metacarpal, sometimes into the trapezium. In Oryeteropus (35, 36) it is inserted into the dorsum of the trapezium. Extensor profundus digitorum.-In Bradypus (1, 2, 3, 4, 5, 6) an extensor indicis, Avhich passes to the most radial of the three digits, is always present. In Cholcepus (8, 9,10) the extensor profundus always gives a slip to the radial of the two digits and sometimes (9, 10) to the ulnar one also. In Myrmecophaga (11, 12, 13) there are slips from the deep extensor to the pollex and index. In Tamandua (14, 15) there is, in addition, a slip to the medius. In Cyclothurus (17, 18, 19, 20) there is always a tendon to the third digit (medius) and sometimes one to the rudimentary |