1000 MESSRS. B. C. A. WINDLE AND F. G. PARSOXS 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 hallucis, 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 

 Choloepus (8, 9, 10) the origin was the same, but the tendon, 

 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 ? tibularis ?), while in 

 Mackintosh's animal (10) it only joined the flexor of the middle 

 toe. Among the Myrmecophagida?, 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 insei'tion was into a sesamoid bone 

 on the inner side of the navicular. In Cyclotliurus (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 fii-st metatarsal and entocuneiform. 



Extensor proprius JiaUucis. — 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 

 and Laurillard (6). In Choloepus (8, 9, 10) a similar condition 

 was observed. Among the MyrmecopTiagidm, Myrmecopliaga (11) 

 and Tamandua (14, 15) have the muscle rising from the lower 

 end of the fibula and inserted into (11, 12, 14) the terminal 

 phalanx of the hallux, but in Eapp's specimen (15) it also went to 

 the second toe. In Cydothuru^ the extensor proprivis 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 Dasyjwdida', 

 Dasypus (22, 23), Tatusia (25), and Ghlamydophorvs (27, 28 a ), 

 the muscle always rises from the lower part of the fibula and is 



