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



i me inch anterior to the posterior angle. In the Arctoccphali the ridge extends from the glenoid to 

 the posterior angle, and is distinct ; but the surface between it and the axillary border is limited. 

 In the Phocinse and Arctoccphali the long head of the triceps and the dorsi-epitrochlear arise from 

 the ridge ; from the large surface in the Phocinse posterior to the ridge only the teres major springs ; 

 as the corresponding surface for the same in Arctoccphalus is limited, it has a linear origin one inch in 

 length at the posterior angle. The insertion of the teres major is enormous, for it takes up about 

 one-third of the length of the shaft. Professor Humphry and I do not find it going to the tuber 

 major like Professor Lucae. The difference between Arctoccphalus and Otaria is in the insertion ; 

 in the latter it goes to the internal condyloid ridge with the dorsi-epitrochlear and first head of the 

 triceps. In the Trichcchus it is similar to Arctocepludus. The mode of junction of the teres ninjoi 

 and latissimus dorsi is interesting ; over the posterior border of the teres tendon the inner part of 

 the latissimus dorsi expands upon and is interwoven with the fascia over the dorsal surface of the 

 teres, and the two thus associated go on to the humerus, the tendon of the latissimus lying next 

 the bone. In the Phocinse it is supplied by the subscapular, in Arctoccphalus by the circumflex. 

 In all the specimens it draws the humerus downwards, inwards, and backwards. 



The Anterior Brachial Eegion in the Phocinse and Arctoccphalus is composed of the biceps 

 and brachialis anticus. The coraco-brachialis is wanting. 



The Biceps is a short muscular band lying on the internal surface of the humerus. It arises 

 from within the capsule of the shoulder-joint by a strong short tendon from the rudimentary 

 coracoid or beak above the glenoid cavity ; and passes out of the capsule below the transverse 

 ligament stretching from the greater to the two lesser tuberosities. It descends between the two 

 tubers, and fills the bed of the wide bicipital groove ; after dipping between the brachialis anticus 

 and the pronator radii teres, it forms a tendon which is inserted into the radial tuberosity on the 

 posterior border of the shaft. The external side becomes anterior at its attachment. 



In Arctoccphalus, besides the one tendinous head, it arises from the edge of the glenoid cavity 

 on both sides of the beak, and is closely united with the under surface of the anterior part of the 

 capsule above the head of the humerus. The tendon emerges from the capsule between the greater 

 and lesser tuberosities, and passes below the tendon of the first part of the supraspinatus, and 

 under the transverse ligament as in Phoca. It then continues down the humerus as a flat muscular 

 band, partly tendinous on its under surface, filling the bed of the enormous bicipital groove. It 

 dips between the pronator radii teres and the inner part of the brachialis anticus, to reach the 

 bicipital tuberosity of the radius into which it is inserted. The external side is also anterior at the 

 attachment into the radius. 



The coracoid is separate in young Seals from the glenoid, and in them is found to form a con- 

 siderable part of the glenoid cavity. If in the adult the coracoid were taken from the ovoid-shaped 

 glenoid it would make a decided break in its shape. When the cartilage is attached to the glenoid 

 it also covers a part of the coracoid. The glenoid and coracoid were inside the capsular ligament of 

 the joint in the Seals dissected, and it is the coracoid that principally gives origin to the biceps. 



In the Phocinse it is supplied on the anterior lower surface by a small branch of the median 

 nerve, and on the posterior surface by the external cutaneous. In Arctoccphalus it is supplied by 

 the musculocutaneous nerve. In all the specimens it flexes the forearm, and when the manus is 

 in pronation it will turn it outwards. 



