DB. J. MUEIE OX THE FOEM AND STEUCTUEE OF THE MANATEE. 165 



catory and lingual apparatus, then, I propose to append to the remarks of Rapp, Vrolik, 

 and Stannius reference to sketches of the palatal and mandibular arches. These I have 

 had illustrated, I believe for the first time, both as viewed in conjunction, in a longi- 

 tudinal vertical section (fig. 37, PI. XXVI.), and as separated (PI. XXII. figs. 18 & 19). 

 I shall also oiFer some observations on the composition of the parts, particularly as 

 respects the so-called horny plates, and their bearings towards those of the edentulous 

 Rhytina stisUeri. 



If the section made lengthwise through the cranium, and slightly to the left of the 

 median vertical line, as given in fig. 37, be examined, the relations of the parts will be 

 easily comprehended. Confining a survey to the mouth-cavity, the lower lip, with its 

 sinuous, bristle-clad, thick epidermis, points forwards. Each bristle springs from a 

 considerable-sized lenticular hair-sac. The fibro-muscular tissues beneath are unusually 

 well developed. The mandibular pad (?'. e. inner lower lip) is composed deeply of a 

 thick gristly or fibrous layer, and a thinner superincumbent epidermis. In front it is 

 separated from the outer lip by a deepish furrow, and behind stops short at the tip of 

 the tongue, though, as afterwards shall be shown, it is continuous with the gums. The 

 tongue is bound down behind the pad, and is incapable of being protruded. Fonvards, 

 from the soft membranous uvular curtain, the fleshy palate, to just in front of the 

 molars, is only moderately thick, whence it by degi'ees increases in thickness and fills 

 the deep concavity of the premaxillary bones, its anterior smoother portion forming the 

 upper inner lip-pad. This latter is separated by a deep furrow from the true bearded 

 lip and truncated muzzle. The palate and the said pad are equally made up of a thick 

 substratum of firm fibro-elastic material overlain by much thinner derm and epiderm. 

 What has been termed the horny plate is alone distinguishable by warty elevations. 

 The lips and cheeks, from opposite the superior pad backwards to the front molar, have 

 a clothing of long stiffish hairs, thickest set along the outer border of the gum ; these 

 are chiefly directed downwards and backwards. 



Turning now to the view of the mandible when removed (fig. 18), the outer true lip 

 is notably dotted with short truncated bristles and longer hairs. The coriaceous pad 

 has a deep and straight longitudinal median groove its whole length. Each moiety of 

 this is again partially divided by a wavy but shallower furrow, which anteriorly and 

 posteriorly curves outwards. The outer raised segments of the pad are only moderately 

 roughened — but the inner ones remarkably so, being studded with short, erect, hard 

 papillae of two sorts. The larger kind are conical, and about 0'5 inch high; the 

 smaller setose sort are nearly as long, and abundantly fill the interstices between the 

 first mentioned. 



The tongue quite agi'ees with Rapp's statement, having long brush-like retroverted 

 filiform papillae towards the tip, many irregularly dispersed and different-sized fungi- 

 form papillae, and a very numerous, closely arranged, double set of circumvallate glands 

 situate at the root. The series of circumvallatse, as noted by him, also extends Unearly 



