56 PROCEEDINGS OF THE NATION" AL MUSEUM vol. 73 



Arctocephahis^ the eleventh rib. The description for Odohenus is 

 obscure. 



Mm. intercostales externi (figs. 18, 19) in the Zalophus were extensive 

 and covered all the intercostal spaces except a part of these that lay 

 deep to the sternocostalis. In the Phoca the external intercostals 

 between the first three ribs did not reach much beyond the bony 

 part of the costae, but caudad therefrom they gradually approached 

 nearer the sternum. 



Mm. intercostales interni exhibited no peculiarity save that the lateral 

 fibers almost met over the ribs. 



M. sternocostalis (figs. 18, 19) (supracostalis Murie, transversus 

 costarum latus Lucae) in the Zalophus arose deep to the pectoral 

 mass from the sternum between the first and fourth costae. Inser- 

 tion was by two slips passing to the lateral (dorsal) part of the 

 first and second costal cartilages. In the Phoca it arose from 

 the manubrium and first two sternebrae, and insertion was upon the 

 first costal cartilage. Miller reported this slightly more extensive 

 in the animals which he dissected, but Murie found it essentially 

 the same as I did. No sternocostalis posterior, such as Miller found 

 in Phoca mtvlina between the third and seventh ribs, was encoun- 

 tered by me. 



Levatores costarum muscles were noted in both genera, but were 

 not followed, nor were any of the muscles within the thorax sought. 



MUSCLES OF THE ABDOMEN 



M. rectus abdominis (figs. 11, 18, 19) in the Zalophus was rather 

 weak. It arose from the symphysis pubis and adjoined the mid- 

 ventral line only as far craniad as the ninth rib. Thereafter slips 

 inserted progressively upon the eighth, seventh, sixth, and fifth ribs, 

 none of these being in contact with the sternum. In the Phoca 

 it was relatively much broader and stronger. Discernible muscle 

 fibers disappeared from its medial part at the fifth and from the 

 lateral border at the third rib, from which point a broad tendinous 

 sheet extended with a medial inclination to the sternum as far 

 craniad as the first rib, but not to the presternum. In Eumetopias 

 insertion was upon the sixth rib. Minor differences of insertion 

 occurred in the specimens dissected by Miller, save that in Phoca 

 vitulina the broad tendon of insertion also extended laterad to the 

 humerus. 



Because of excessive contraction of the thorax in the Zalophus. 

 the other abdominal muscles were much wrinkled. They were thus 

 very difficult to dissect, and as the preservation of this region in 

 the Phoca was poor, all parts, especially craniad, were not completely 

 investigated. 



