MOUTH AND NOSE 



size of these pads is chiefly for the purpose of maintaining the nares 

 in a closed position. The large pads of Potomogale, otters and phocids, 

 by their bulk and elasticity crowd the narial apertures so that in their 

 fullest development little or no muscular effort is necessary for closure. 

 If effort be necessary, then it can be supplied by the radiating fibers 

 of the pad itself and by tension of the naso-labialis muscle. In the 

 fissipeds and pinnipeds the pad pressure is largely in a medial direc- 



FIGURE 12. Pharyngeal region of the pigmy sperm whale Kogia, from above 

 (redrawn from Kernan and Schulte) ; (a) tongue; (b) nasopharynx; 

 (c) oropharynx; (d) larynx; (e) arco palato-pharyngeus ; and (/) esopha- 

 gus. 



tion, while in Potomogale it would seem to be chiefly anteriorly. The 

 reason for the latter condition is that in this insectivore otter there is 

 a bilobed rhinarial shield, smooth and evidently firm in life. The nasal 

 passages are situated posterior to this while the openings are to the 

 sides of the shield. Hence, pulling the very broad mystaceal pads to 

 the rear opens the nostrils, and relaxation presses them firmly against 

 the shield. 



[89] 



