REPORT ON THE SEALS. 149 



posterior border of the flipper, and the anterior border of the radius about its middle. 1 The abdominal 

 part, after disappearing beneath the sternal, is joined by the outer division of the latisshnus dorsi, 

 and then joins the portion of the sternal part which is inserted into the humerus. The humeral 

 portion is muscular on the under surface in the upper third and tendinous in the lower two-thirds. 



In Arctoccpludus gazella there are also three parts having almost similar names. The pre- 

 sternal part is most anterior, and consists of a narrow muscular band. It arises from the lateral 

 anterior termination of the presternum by a small tendon. It is half under cover of the sternal 

 part, and courses almost transversely outwards to the shoulder over the sterno-cleido-mastoid, 

 which descends behind its inner half to gain the fascial slip occupying the position of the absent 

 clavicle. The outer half is between this muscle, which is now ventral to it, and the sternal part. 

 Over the shoulder it is lost among the fibres of the stemo -mastoid above and the sternal part be- 

 hind. 2 The sternal part lies posterior to the presternal, and anterior to the thoracico-abdominal, 

 partly covering it. It is a fleshy mass of transverse fibres of considerable depth and breadth. It 

 arises from the lateral half of the presternum and meso-sternum ; and from the cartilages of the 

 four anterior ribs. It blends over the presternum and meso-sternum with the same part of the 

 opposite side. The fibres reach the anterior border of the humerus in a sheet of the same breadth 

 as at the origin. This wide bundle is inserted in its anterior half after blending with the thoracico- 

 abdominal part into the inner lip of the deltoid ridge of the humerus. The anterior three- 

 fourths of this insertion pass beneath a slip of the sterno-cleido-mastoid, which is adherent to the 

 pectoral, and end by dividing into two ; the outer slip becoming confluent with the origin of the 

 inner part of the brachialis anticus, and the inner by ending similarly upon the pectoral. The 

 posterior half is inserted obliquely into the deep fascia of the forearm, from the anterior side of 

 the bend of the forearm to the middle of the posterior border of the ulna. It is also attached 

 to the cartilaginous bar over the outer side of the forearm near the elbow-joint. The thoracico- 

 abdominal part is a large strong triangular sheet with the base in the mesial plane. It arises by 

 two divisions ; the ventral from the linea alba 1 inch behind the xiphi-sternum, and from the 

 outer half of the xiphi-sternum. This soon blends with the dorsal, which arises from the cartilages 

 of the 2nd to the 11th ribs ; from the 8th to the 11th ribs, opposite to the origin of the 

 ventral division, it only springs from the cartilages ; but anterior to the 8th rib it also has 

 origin from the side of the meso-sternum, and blends with its fellow as far forwards as the 4th 

 rib. Anterior to this, it does not blend over the meso-sternum ; for the sternal part intervenes 

 between the origins of the thoracico-abdominal parts of the opposite sides. The fibres pass to- 

 wards the humerus, partly under cover of the sternal part ; the posterior fibres ascend, the anterior 

 are transverse. At the level of the 5th rib laterally, the outer division of the latissimus dorsi 

 blends with it. After gaming these fibres along its outer edge, it blends with the sternal part and 

 is inserted with it. The under surface of the insertion is tendinous. 



As a guide to the descriptions of this muscle in Phoea xitidina, Arctocepludus gazella, Of",'-- 

 and Trichechus, a statement of the names used for the various divisions may be useful, as anatomists 

 differ much in their nomenclature. 



In Phoea vitulina there are three parts — (1) the Presternal, (2) the Sternal, (3) the Abdominal. 



1 The deep fascia over the anterior surface of the forearm divides into two layers — the anterior one gives attachment 

 to the panniculus, as has already been stated ; the posterior is for the pectoral muscle. 



2 The fascial slip representing the clavicle is attached to the presternum internally, and passes outwards beneath 

 the inner half of the presternal part of the pectoral, to end by joining the sterno-cleido-mastoid going to the humerus. 



