EEPORT ON THE SEALS. 173 



extends and abducts ; it therefore acts like the extensor communis digiti secundi in the Phocinae, 

 It may be as well to note that the Phocinae have a tendon from the extensor primus to 

 the 5th digit, as is seen in Arctocephalus, but not in Otaria and Trichcchus. The actions are as 

 usual. 



The Tensor of the posterior annular ligament, named by Lucae tensor ligamenti carpi dorsalis 

 communis, springs from the extensor communis digitorum secundus, near the external condyle, and 

 consists chiefly of a narrow tendinous band. It is inserted into the middle of the upper edge of 

 the outer or posterior annular ligament. In Phoca hispida and Phoca barbata it could not be made 

 out owing to the condition of the specimens, but is most likely present in them. On referring to the 

 accounts of Otaria and the Walrus it will be seen that in them the extensor minimi digiti and extensor 

 medii digiti form one set of the extensors, and as the tensor comes out of the same set, I consider it 

 to be the representative of the extensor medii digiti of the Sea Lion and Walrus. 



The Extensor carpi ulnaris in the Phocinae arises from the external condyle, from the outer 

 surface of the ulna beside the articular facet for the radius ; and from the ligament of the joint. 

 It passes through the fifth division of the annular ligament ; and is inserted into the middle of the 

 ulnar side of the 5th metacarpal bone. 



In Arctocephalus the anconeus externus partly covers its origin. It arises from the external surface 

 of the olecranon, between the anterior and middle tubercles (PL VII. fig. 4) ; and from the outer edge 

 of the quadrilateral surface behind the great sigmoid cavity of the ulna. It descends to the carpus 

 on the inner side of the externus, and, after crossing the extensor proprius pollicis, is inserted into 

 the base and head of the ulnar side of the 5th metacarpal, but chiefly into the head of the first 

 phalanx on the ulnar side. In Otaria and Trichcchus it is inserted only into the 5th metacarpal. It 

 extends the manus, powerfully abducts it, stretching out the digits, besides aiding extension of the 

 forearm. It is supplied by the posterior interosseous nerve. 



The Supinator brevis arises from the external condyle of the humerus, and from the ligament of 

 the elbow-joint on the external surface. It is inserted into the upper two-thirds of the anterior 

 border of the radial shaft, into the anterior third of the inner surface down to the pronator teres 

 insertion, and into the anterior two-thirds of the outer surface to the same insertion. 



In Arctocephalus this muscle is hidden on the outer aspect of the radius by the downward 

 expansion of the extensive lateral ligament. It arises from the posterior and external surface of 

 the external condyle below the external lateral ligament, from the posterior aspect of the capsular 

 ligament covering the posterior surface of the condyle, from the capsule over the outer side of the head 

 of the radius, also from the outer half of the capsule covering the anterior aspect of the head of the 

 radius, and slightly from the front of the capsule covering the anterior side of the external condyle. 

 The fibres from the back of the condyle are mostly tendinous, and all are parallel to the radial 

 shaft. It is inserted into the anterior half of the neck on its outer surface, into the external surface 

 of the shaft of the radius, as far down as the lowest fibres of insertion of the pronator radii 

 teres, that is about the middle of the bone ; into the neck of the shaft of the anterior border to 

 the insertion of the same muscle, and slightly into the inner border below the neck. 



In Trichcchus, as in Arctocephalus and the Phocinae, it has only one head of origin, but in 

 Otaria it has two heads, the additional one from the ulna below the coronoid process. It supinates 

 the forearm and steadies the joint. It is supplied by the posterior interosseous nerve. 



In Arctocephalus the Extensor proprius pollicis covers a considerable part of the flexor carpi 



