r 
Mackintosh— Ow the Myology of the Genus Bradipui, 523 
from those parts, supplies the place of the three ordinary flexors of the 
hand, and terminates in three very strong tendons passing under the 
annular ligament, which was also very strong, and inserted into the 
last phalanges of the three digits, which could be easily extended to a 
right angle with the palm. In Professor Macalister's specimen the 
muscle was indivisible, and the digits could not be extended to aright 
angle with the palm without tearing. 
Supinator longus ('41) is in two parts, the longest inserted into the 
lower half (lower extremity. Professors Macalister and Humphry) of 
the radius, and by tendon (by a few fibres, Professor Macalister) into 
the external lateral ligament of the wrist. The shorter portion was 
inserted into the fascia over the wrist. 
Supinator brevi sis small, pierced by the posterior interosseous nerve, 
origin humeral, insertion radial. Professor Humphry describes this 
muscle as being large in his specimen. 
Extensor carpi radialis ('10) is single, arising from the external 
condyle, and inserted into the second metacarpal. In B. tridactylus 
there are two tendons of insertion, one to the first, and one to the 
second metacarpal, evidently representing the longer and shorter 
radial extensors of the wrist as found in most other animals. 
Extensor carpi ulnaris ('04) is a small muscle, taking origin from the 
outer condyle and olecranon process, and inserted into the base of 
the third metacarpal. Professor Macalister describes its origin as 
being humeral only, and Professor Humphry found two muscles, one 
tendinous in origin, from the outer condyle, and inserted into the back 
of the distal end of the middle metacarpal, the other arising slightly 
from the condyle, but chiefly from the ulna is inserted into the base of 
the outer metacarpal. 
Extensor digitorum communis (-04) arises from the external 
condyle of the humerus, and is inserted into the dorsal aponeurosis 
of the hand, and by fascia along the backs of the three digits. The 
outer finger had not this prolongation in Professor Macalister's speci- 
men. 
Extensor ossis metacarpi poUicis (*11) takes origin from the second 
and third fourths (middle, Professor Macalister) of the back of the ulna, 
and is inserted into the base of the inner metacarpal. Professor 
Humphry describes it under the name of extensor pollicis primus as 
extending from the ulna to the trapezium. 
Extensor indicis ('05) arises from the lower third of the ulna, and 
is inserted into the base of the inner metacarpal. Professor Macalister 
describes it as extending from the lower extremity of the ulna to the 
base of the first phalanx of the inner digit, and Professor Humphry 
found the same insertion, but the origin from the middle of the 
ulna. 
Extensor minimi digiti arises from the outer condyle of the humerus, 
and is inserted into the third metacarpal. It was absent in B. 
tridactylus. 
R. I. A. PROC. — vol.. I., SER. II., SCIENCK. 3 Y 
