166 DR. J. MUfilE ON THE POEM AND STEFCTUEE OF THE MANATEE. 



and laterally forwards to the anterior third of the organ, and they lie in close approxi- 

 mation with the dental portion of the gum. 



In the younger male the lengths of the tongue and symphysial pad mesially were 

 3-2 inches and 1-4 respectively, in the female 4 inches and 2; the breadth of the 

 tongue of the latter was 0-8, and the widest portion of the inferior pad 1-3 inch. 



On the palato-dental arch (fig. 19) the cheeks and lips, as before mentioned, are 

 bestrewed with hair and short stiff bristles. These latter form a scattered row, reaching 

 from the upper external labial clump (seen on the front of the muzzle, figs. 6 & 7) 

 backwards slightly beyond the angle of the mouth. The thick brush of hairs in the 

 deep hollow just outside the palate is well shown in fig. 19, hh. The long narrow 

 palate is divisible into three portions. The anterior, somewhat horseshoe-shaped, is 

 the smoothish, convex, elastic pad regarded by some as the inner upper lip. The 

 middle portion is the rasping homy plate, which is slightly concave longways and 

 across, and does not extend to the front molar by half an inch. Its surface is very 

 rough and warty-looking, being almost entirely covered by thick, flattish, V-shaped, 

 retroverted elevations. Some of these are rounder than others on the summit, many 

 are acerate, and all are fringed by short setse from base to tip. The intervening palatal 

 spaces have a less rasping surface, but are not altogether smooth. The largest V-shaped 

 papillse in the female measured 0-2 inch long and 01 inch in diameter at the base. 

 In front and behind their size diminishes as they merge into the smoother anterior pad 

 and posterior palate. The posterior third portion is equal to the preceding two in 

 length, and is smoother ; in it there is a longitudinal mesial and linear elevation, which 

 runs backwards from opposite the anterior molar tooth. 



Leaving the histological consideration of these buccal appendages and mouth-arma- 

 ture for further inquiry, I shall meantime, in the superficial relations of parts, compare 

 what obtains in the other Sirenian genera and some neighbouring orders of mammals. 



According to Huxley', Messrs. Quoy and Gaimard^ first paid attention to the horny 

 jaw-plates of the Dugong. Be this as it may, from theii- and subsequent researches it is 

 now known that in IlaJicore bristles and hairs are found in the mouth almost identical 

 in position with those above described. The bent-down symphysial portion of the 

 mandible and palatal surface of the premaxillaries are also each covered by a coriaceous 

 tuberculated plate ; and the tongue is bound down behind. Both Dugong and Manatee 

 possess a series of molar teeth ; and in both, upper and lower incisors are present. But 

 it is further to be observed that these latter bear a gradated development, inasmuch 

 as in Manatus they are quite rudimentary, only discovered in the foetus, and never 

 protruded, whilst in Halicore they are diminutive and functionless in the female, but 

 two upper ones in the male form powerful tusks. 



With respect, therefore, to the formation of the lips, mouth-armature, and dentition, 

 the homologous parts coexist in the above two forms. 



' Hunterian Lectures, Lancet, 1866, p. 180, ^ Voyage de I'Astrolabe, 1830, vol. i. p. 146. 



