166 DR. J. MURIE ON THE FORM AND STRUCTURE 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, 6h. 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 horny 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 sete from base to tip. The intervening palatal 
spaces have a less rasping surface, but are not altogether smooth. The largest V-shaped 
papille in the female measured 0-2 inch long and 0:1 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 their and subsequent researches it is 
now known that in //alicore 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. 
1 Hunterian Lectures, Lancet, 1866, p. 180, ? Voyage de l’Astrolabe, 1830, vol. i. p. 146. 
