1899,] THE MYOLOGY OF THE EDENTATA. 997 



interna] condyle and the inner head of the gastrocnemius. 

 Myrmecophaga (11, 12) and Tamandua (14, 16), amongst the 

 Mynnecophagidce, have also perfectly distinct representatives of 

 this muscle ; and in Cyclothurus (17, 19, 20) it is also evidently 

 present. Galton (20) speaks of it as a second head of the semi- 

 tendinosus. In the Dasypodidce, Manidce, and Orycieropodidce the 

 muscle is also evidently present, but seems to be rather more 

 closely united with the semimembranosus. 



Semitendinosus. — The chief point of interest about this muscle is 

 the varying presence of ischial, caudal, or both heads. In the 

 Brudypodidm, Brculypus (1, 2, 4, 5, 6) and Choloepus (8, 9, 10) 

 possess only the origin from the tuberosity of the ischium, the 

 insertion being as usual into the upper part of the internal 

 surface of the tibia. In the Myrmecophagidce, our specimen of 

 Myrmecophaga (11) was especially interesting in that in it the 

 caudal and ischial origins remained separate right down to their 

 insertions, and so formed two distinct muscles. The first of these 

 (semitendinosus anterior) rose from the tuber ischii, and was 

 inserted into the internal tuberosity of the tibia just below the 

 insertion of the semimembranosus. The second (semitendinosus 

 posterior) rose from the anterior caudal vertebrae, continuing the 

 origin of the caudo-femoralis, and was inserted into the tibia just 

 below the last. Both these muscles were supplied by the great 

 sciatic nerve. In Tamandua (14, 15) only the caudal head was 

 preseut. In Cyclothurus (17, 20, 21) the caudal head was alone 

 present, but in another specimen (19) the ischial head was the 

 only one found. Among the Dasypodidce, Dasypus (22, 23) and 

 Chiamydophorus {21, 28 a) had only the ischial head, but in 

 Tatusia (25) both ischial and caudal heads were present. A strong 

 prolongation, extending to the heel, from the insertion of the 

 muscle was noticed in Dasypus (22). In the Manidce (29, 32, 33, 

 34) the caudal head is always present, and in two instances (33, 

 34) an ischial head was also found, though it was small in the 

 first-mentioned specimen. In the Orycieropodidce (35, 36, 37) 

 the ischial head alone was found, and the same prolongation to 

 the heel already alluded to in Dasypus was noticed. It will thus 

 be seen that the ischial head is alone present in the Bradypodidce and 

 Orycteropodidce ; it is also always preseut in the Dasypodidce, though 

 occasionally accompanied by a caudal head. In the Manidce the 

 caudal head is always found, and the ischial, if present, is sub- 

 sidiary ; while in the Myrmecophagidce either ischial or caudal, or 

 both heads may appear. The presence of a tendinous intersection 

 in the muscular belly of the semitendinosus has evidently been 

 sought for by many of the dissectors of these animals, but so far 

 we have only found its presence recorded in one specimen of 

 Chiamydophorus (27) described by Macalister. 



Flexor cruris lateralis {Biceps femoris). — Among the Brady- 

 podidce, Bradypus (1, 2, 4, 5) and Choloepus (8, 9, 10) have the 

 muscle rising from the tuberosity of the ischium, but not from the 

 caudal vertebrae. The insertion is usuallv into the fascia of the 



