REPORT ON THE SEALS. 143 



and is fixed to a tubercle at the outer edge. What is found in the Seals is a complete division 

 of the muscular sheet resembling the human trapezius into three muscidar masses — (1) the 

 cephalo-humeral, which represents the clavicular fibres of human anatomy ; (2) the trapezius 

 anterior part, the fibres fixed to the spine; and (3) the trapezius posterior part, the fibres 

 forming the tendon attached to the tubercle. 



The Ccphcdo-humcral as in the Carnivora generally forms a bulky mass. It is triangular, the 

 base rests upon the ligamentum nuchas, and the apex upon the shoulder, and is under cover of 

 the cervico-scapular part of the panniculus. It arises from the occipital ridge, from the fascial 

 slip anterior to the ligamentum nuchas, and from the anterior half of the ligamentum nuchas. 

 The fibres trend oblicmely backwards and outwards, and cover the side of the neck ; at the 

 shoulder they converge and are inserted by a short tendon into the upper end and anterior edge 

 of the great humeral tuber above the pectoral insertion, with which the tendon blends; and into 

 the transverse ligament, stretching between the two tubera over the biceps. The fibres are a little 

 coarser than those of the trapezius ; there is a cellular interval between the cephalo-humeral and 

 the anterior part of the trapezius, which is not distinct, but continuous. Above the shoulder the 

 atlanto-humeral muscle appears between the anterior part of the trapezius and this muscle, before 

 it reaches the hmnerus. From the shreds of this muscle traced in Phoca barbata and in Phoca 

 hispida it appears to be disposed as in Phoca vitulina. 



In Arctocephalus gazclla the lacerated condition of the muscle in both specimens compels me 

 to pass over the origin. The muscle is larger and better developed than in the other specimens ; 

 it extends from the head to about 1 inch posterior to the anterior angle of the scapula, and 

 partially overlaps the anterior part of the trapezius ; above and behind the shoulder it forms a 

 broad muscidar band of which the anterior two-thirds blends with the sterno-mastoid, whereas 

 in the Phocinas it only touches the trapezius, and is a small bundle of muscle near its insertion. 

 It is inserted into the humerus between the insertion of the deltoid posteriorly, and the insertion 

 of the sterno-mastoid anteriorly. 



Professor Humphry in his description does not use the names cephalo-humeral and trapezius, 

 anterior and posterior parts, but includes the whole mass under the name trapezius. 



In the Phocinas and Arctocephalus the cephalo-humeral pulls the humerus forwards and rotates 

 it inwards ; this action is much greater in the latter, for the insertion is lower down upon the 

 shaft, and it also abducts. In the Phocinas it is supplied by the spinal accessory nerve. In 

 Arctocephalus the nerve was destroyed ; both receive branches from the cervical nerves. 



The Trapezius (proper) is in two parts, an anterior and a posterior. 



The anterior part with its fellow of the opposite side forms a trapezium. It is opposite the 

 vertebral border of the scapula, and arises from the posterior half of the ligamentum nuchas, 

 from the spines of the first six dorsal vertebras, and from the supra-spinous ligaments. The fibres 

 of this muscle are distributed in a threefold manner. The most anterior fibres pass anterior to 

 the scapidar spine at its axillary termination, and are partially concealed by the atlanto-humeral 

 muscle before being inserted into the anterior surface of the great humeral tuber, to the inner side 

 of this muscle; a few fibres do not reach the bone but blend with the atlanto-humeral. The 

 posterior fibres attach themselves to the vertebral end of the spine. The ones intervening between 

 the most anterior fibres and the posterior must be studied in two layers, a superficial, and a deep. 

 The superficial layer passes over the scapular spine and terminates upon the surface of the deltoid. 



