700 MR. T. MANNERS-SMITH ON THE [Dec. 4, 



tendon and from the sesamoid bones in the tendon. They ter- 

 minate in very slender tendons, which, after resting upon the 

 corresponding tendon of sublimis, spread out into a thin fascia 

 which blends with the digital sheaths of the profundus. The first, 

 third, and fourth are larger than the second, which is very small. 

 The first is more probably an abductor than a flexor of the pollex. 

 The others give off two slender fascial slips, one on each side of 

 the profundus tendon, to first phalanx, and send a third slip 

 forwards to blend with the digital sheaths of the tendons of 

 profundus. This muscle is not mentioned by Owen. Mivart 

 says that flexor brevis is most probably absent in Ecliidaa and 

 OrnitJiorhynchus. Whilst the origin of a sublimis from the tendon 

 of a profundus is common in Amphibians, it is rare amongst 

 Mammals. 



Flexor carpi radialis is a large muscle. It arises from the lower 

 end of the internal condyle, and is inserted below into a fairly 

 large radial sesamoid bone. From the sesamoid bone slips pass 

 on the radial side to the scapho-lunar and trapezium ; on the 

 ulnar side to pisiform and, downwards, to second metacarpal. 

 The muscle is supplied by the median nerve. In Echidna this 

 muscle passes to metacarpal bones of pollex and index. 



Pronator radii teres. — Arises from the inner condyle of humerus. 

 It is inserted into middle of radius, a little below and on the 

 opposite surface to supinator brevis. 



Flexor carpi idnaris is a large flat muscle, arising by two heads 

 from the internal condyle of the humerus : from the posterior 

 border of the ulna and expanded upper extremity of olecranon. 

 The tendon is inserted into the pisiform, and sends slips to the 

 fourth and fifth metacarpals. This muscle is supplied by the 

 ulnar nerve. 



Supinator brevis. — This is a somewhat triangular muscle. It 

 arises from the external condyle, beneath the radial extensors of 

 the wrist. It is inserted into the upper and middle fourths of the 

 shaft of the radius. It is supplied by the posterior interosseous 

 nerve. This nmscle is not mentioned by Owen. 



Extensor carpi radialis longior. — Arises from the lower third of 

 the supinator side of the shaft of the humerus. Below it divides 

 into three tendons, which pass to the bases of the second, third, 

 and fourth metacarpal bones. 



Supinator longus. — Arises from the lower end of the humerus, 

 beneath the longior. It is inserted into the posterior surface of 

 the peculiar large scapho-lunar. The muscle having this origin 

 and insertion in Echidna is described by Mivart as the extensor 

 carpi radialis longior. Only one radial extensor is described by 

 Owen in OrnitJwrhyncJius corresponding to longior. Supinator 

 longus is not described by him. 



Extensor communis digitorum. — Arises by a common tendon 

 from the external condyle. It expands on the back of the wrist, 

 the expansion containing a fibro-cartilage. The expansion divides 

 into two parts, each part giving off three tendons. Two go to the 



