336 MESSES. B. C. A, WINDLE AKD P. G. PARSONS ON [Mar. 7, 



Tatusia (25, 26), and Glilamydopliorus (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 Onjcteropodiclce 

 (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 two specimens of Bradijpus (2, 3) out of live examined, and in 

 one specimen of Chol(xpus (9) out of three. In the cases in which 

 an extensor brevis was not present, it was replaced by a normal 

 extensor minimi digiti, which obtained an insertion into the most 

 ulnar digit. In MyrmacopJiaya (11, 12) the muscle in question 

 only went 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 Ghlamydophorus 

 (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 was 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 Oryct.iropus the extensor minimi 

 digiti is inserted into the minimus and annularis (35, 37) or into 

 the minimus alone (36). 



Extensor carpi idnaris. — 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 Gholoepus (8, 9, 10) have this muscle in- 

 serted into the trapezium, though in Mackintosh's specimen (5) 

 the insertion is said to have been into the base of the inner meta- 

 carpal. 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 some- 

 times is inserted into the first metacarpal, sometimes into the 

 trapezium. In Orycteropus (35, 36) it is inserted into the dorsum 

 of the ti'apezium. 



Extensor profundus digitorum. — In Bradypus (1, 2, 3, 4, 5, 6) 

 an extensor indicis, which passes to the most radial of the three 

 digits, is always present. In Gholospus (8, 9, 10) the extensor pro- 

 fundus always gives a slip to the radial of the two digits and 

 sometimes (9, 10) to the ulnar one also. In Myrmecop)haga (11, 

 12, 13) there are shps from the deep extensor to the pollex and 

 index. In Tamandua (14, 15) there is, in addition, a slip to the 

 medius. In Gyclothurus (17, 18, 19, 20) there is always a tendon 

 to the third digit (medius) and sometimes one to the rudimentary 



