24 PROCEEDINGS OF THE ISTATIONAL MUSEUM 



Sternum. — In essential features the sternal complex of Zalophus 

 and Phoca\ are largely similar. In these two skeletons all of the ele- 

 ments are articulated and the bony portions (exclusive of presternal 

 and xiphoid cartilages) constitute in Zalophus 56, and in the Phoca 

 but 37 per cent of the trunk length (41 in a cat). In the Phoca 

 skeleton there is a long, slender presternal cartilage which is two 

 and a half times the bony part of the sternum and 71 per cent of 

 the whole manubrial complex. In the ZalopJius a similar result has 

 been attained but chiefly by anterior extension of the bony part of 

 the manubrium. Thus, in the Zalophus the latter is 22 per cent 

 (17 in the Phoca) of the bony sternum, but the presternal carti- 

 lage is insignificant, and but 30 per cent of the size of the manubrium 

 proper. The presternum of Phoca projects relatively farther for- 

 ward than in the otariid, however. The bony manubrium is longer 

 in the latter (over twice the length of the first sternebra), but in 

 both the first pair of costal cartilages arises from lateral processes, 

 in the Zalophus caudad and in the Phoca rostrad of the middle of the 

 bone. In the former there are six and in the latter seven sternebrae. 

 In the Zalophus only, the last of these has a pair of broad facets for 

 the attachment of the costal cartilages. In this genus the xiphoid 

 or enciform bone is relatively shorter but its cartilage is longer than 

 in Phoca. 



Ribs. — As already mentioned, there are 15 pairs of ribs in both 

 animals, which is normal for otariids and phocids, but Odohenus 

 has only 14. Attachment to the vertebral column of the first 10 

 pairs is both capitular and tubercular, and capitular onlj^ in the 

 case of the last 5. The relative stoutness and shortness of the first 

 rib is more accentuated in the Phoca. In Zalophus the first eight pairs 

 of costal cartilages are securely attached to the sternum, while in the 

 Phoca there are nine, there being in this genus one more sternebra. 



EXTREMITIES 



Pectoral girdle.— This is incomplete in the pinnipeds, there being 

 no clavicle. The scapulae of the Zalophus and Phoca are very dif- 

 ferent. In the former the supraspinous fossa is two or more times 

 the size of the infraspinous, the coraco-vertebral angle is well defined, 

 and the vertebral border extends definitely caudo-ventrad. In the 

 Phoca there is no coraco-vertebral angle proper, this part of the 

 scapula being evenly curved, and to this extent the supraspinous 

 fossa is reduced. The gleno-vertebral part of the infraspinous space 

 (so termed to differentiate it from the more circumscribed infra- 

 spinous fossa proper, from Avhich arises the muscle of this name) 

 is much lengthened, giving to the scapula its characteristic sickle 



