166 THE VOYAGE OF H.M.S. CHALLENGER. 



In Otaria the deep and superficial flexors are very different from those of all the other species, 

 since they do not unite in the palm. Tha flexor sublimis digitorum has two heads which join, and it 

 divides into double slips for the 2nd, 3rd, and 4th digits, and a single for the 5th. The flexor profundus 

 digitorum comes from the ulna and radius and divides into two tendons for the pollex, forming its short 

 and long flexors, two short and long flexors for the index, and a single one for the 3rd digit ending 

 like a short flexor. From this short account it is obvious that the names flexor sublimis digitorum 

 and flexor profundus digitorum do not bring out the functions of these tendons, because both act as 

 short and deep flexors. In the Phocinse it is supplied by the median and ulnar nerves, in Arcto- 

 cephalus by the median. It has the usual actions. 



The Palmar fascia in the Phocina?. is a quadrangular piece of fascia attached on its outer 

 border to the outer border of the lower end of the radius, and to the scapholunar bone. It extends 

 to the posterior border of the radius, where the superior angle of this side gives attachment on the 

 under surface to the anterior slip of part one of the palmaris longus. 



The Flexor carpi radialis arises from the internal condyle between the pronator teres and the 

 first head of the flexor communis digitorum. It passes over the carpus, and then the tendon divides 

 into three. The outermost or anterior is inserted into the ulnar side of the base of the 1st 

 metacarpal bone ; the middle into the ulnar side of the base of the 2nd metacarpal bone ; and the 

 innermost or posterior into the base of the radial side of the 3rd metacarpal. 



In ArctocepJudus it arises as in the Phocina?, but is placed between the origins of the pronator 

 radii teres and palmaris longus ; it is connected with the former for about half an inch. It is 

 cylindrical ; about the middle of the forearm it ends in a long, slender tendon which divides into 

 three very short slips. These are inserted into the ligament between the trapezium and trapezoid 

 bones ; into the ulnar side of the proximal end of the 1st metacarpal, beneath the first flexor brevis 

 muscle ; and into the radial side of the proximal end of the 2nd metacarpal. 



In Arctocephalus the origin differs slightly from that in the Phocina? in its relations, and the insertion 

 of the 1st tendon in the former is beneath the flexor brevis into the radial side of the 2nd metacarpal 

 instead of the ulnar side. The 3rd tendon ends over the ligament between the scaphoid and the trape- 

 zoid bones, and is not long enough to reach the radial side of the 3rd metacarpal as in the Phocina?. 



The origins in Otaria and Trichcchus are the same as in Arctocephedus ; the insertion in Otaria 

 is single, being only to the 1st metacarpal. In all, the insertion into the 1st metacarpal is constant, 

 and is the largest and strongest when more than one tendon is present. This gives increased 

 steadiness to the wrist-joint in flexion, which is necessary, because the pollex is not opposable 

 but bound up with the other digits by the integument, and is finger-like in actions. In all the 

 specimens it is supplied by the median nerve. It has the usual actions. 



The Pronator radii teres arises from the internal condyle of the humerus, below the supra- 

 condyloid foramen, and is inserted into the inner surface of the radius, 1 inch from the lower 

 extremity of the shaft, by a quadrilateral bundle of fibres ; and into a very small extent of the 

 inner side of the anterior border, above the supinator longus. 



In Arctocephalus it arises from the condyle as in the Phocina?, but is partly covered by the 

 flexor carpi radialis, and is united with it for half an inch ; and from the internal lateral ligament. 

 It descends as a flat muscle along the internal surface of the radius ; and is inserted into the 

 anterior border of the middle of the shaft for about one inch. In Otaria and Trickcchus it has 

 a slightly different arrangement from that seen in Arctocephalus. 



