MOUTH AND NOSE 



terminal tactile appendage aborted, structurally the manatee's naso-labial 

 organ would assimilate with it." Being derived from proboscidean stock 

 (according to belief) it is perhaps not astonishing that sirenians should 

 have such a highly developed and unique labial equipment. Neither 

 is it surprising to find that in consequence (evidently) of this great 

 mobility of the lips this order is incapable of protruding the tongue. 



In sirenians the ingestion of food is aided by bristles upon the inner 

 lips, hairs and bristles upon the oral cheek surfaces, and fibrous papillae 

 upon both the floor and roof of the oral cavity. These papillae are bet- 

 ter developed in the dugong than the manati, and are said to have been 

 best defined in the extinct Steller sea cow. In the dugong at least, a 

 skinned head of which I examined in the National Museum, the papillae 

 constituted rasp-like surfaces that must be extraordinarily efficient in 

 tearing up vegetable food. This individual also had a most peculiar 

 oral development consisting of a subglobular prominence the size of 

 a small hen's egg upon the ventral part of the rostral tip. This was 

 smooth, and hard and tough in the preserved specimen, but in life it was 

 evidently soft and mobile, functioning as a sort of soft, accessory tongue 

 tip. From Murie's figure the tongue proper of the manati is relatively 

 smooth. 



The adult male walrus is so constructed that it cannot use the fore 

 limbs as an aid to ingestion of food, and unless a morsel is small 

 enough to slip readily between the bases of the huge tusks, difficulty is 

 encountered. The midsection of the upper lip is relatively immobile, 

 and the lower lip seems but slightly muscular and incapable of protru- 

 sion. The difficulty is therefore partly overcome by the mystaceal pads. 

 These are greatly developed, project considerably, are mobile, and fitted 

 with short vibrissae of such large diameter that they are veritable 

 spikes. By a medial contraction of these, food may be forced into the 

 mouth. There is record of a captive walrus having killed and partly 

 eaten a seal, using the bristly pads to tear off flesh — a feat which it 

 would have been entirely incapable of accomplishing without their aid. 



The apex of the walrus tongue is rounded and entire, but cleft in all 

 other pinnipeds, according to Sonntag (1923) . In comparing pinniped 

 with fissiped tongues he stated that in the former the tongue is "shorter, 

 wider, thicker. Apex cleft in all except Trichechus (Odobenus). Edges 

 lobulated or have laterally-projecting papillae. Mucosa of pharyngeal 

 part folded. Many glandular orifices present. Vallate papillae fre- 

 quently absent. Lytta absent. Frenum slight. No trace of a spinous 

 patch or papillae clavatae. Lateral organs variable." He also stated 



[77] 



