10 



PKOOEEDINGS OF THE NATIONAL, MUSEUM 



VOL. 73 



masseter muscles or a corresponding increase in the breadth of the 

 lower jaw, accompanied by certain rather complicated changes, both 

 muscular and osseous, in the region of the palate ; or (b) by a decrease 

 in width of the interorbital septum, to this extent allowing the eyes 

 to roll upward and inward. The interrorbital septum of all pinni- 



preiTux. 



TRACHELOrAAST 

 TE^\POR^US 

 STLRNOIMST. 

 SPLENIU5 PART 



CEPHALOHUMERAL' 



RHOI«\B. ANTICUS^ 



r 



occipital 

 Fig. 2. — Dorsal view of the skull of Zalophus showing areas of muscle 



BWE-NT. Ctnv. 

 RECT. CKP. POST. P\M. 

 RtCT. C^P. POST. WNOR 

 >'f#--^_OBL\a. C^P. SUPER. 



ATTACHMENTS LABELED IN CAPITAL LETTERS ; NAMES OF BONES IN SMALL TYPE 



peds is proportionately thinner' than in existing terrestrial carniv- 

 ores, indicating that even in the Zalophus in which interorbital 

 breadth is 11 per cent of total skull length, dorsal vision is used con- 

 siderably. In the Phoca, however, this is excessively thin, its width 

 dorsad being but 3 per cent of the length of the skull, and more 



