168 DE. J. MUEIE ON THE FOEM AND STEUCTUEE OF THE MANATEE. 



Sirenian manducatory plate. The lower masticatory plate, again, may have its homo- 

 logue in the firm membranous portion of the symphysis, which is toothless. 



In the Eorqual {Physalus antiquonim) bristle-like hairs are met with on the lower 

 lip, and there is a protuberant chin. The mucous membrane of the roof of the mouth 

 is indurated, transversely arched, and about a foot wide behind, but flattened, more 

 callous, and only half the width in froat. The baleen-plates and vasculo-fibrous root- 

 matrix spring from outside the palate, and, though in close relation, are not a diffe- 

 rentiated portion of it. The baleen, in fact, at its hindermost end, is little else than a 

 matted tuft of hairs ; and quite in front it shortens and resolves itself into isolated 

 patches composed of aggregated clumps of bristles, there being mesially a distinct but 

 small-sized pad'. 



We learn, moreover, from the extensive researches of MM. Eschricht and Eeinhardt', 

 that in the foetal and very young Balcena mysticetus short stiff hairs are distributed on 

 the outer anterior surface of the upper and lower lips ; and besides these there are 

 median bald spaces, apparently corresponding to the pads of Manatus. The palate is 

 much narrower than in Balmnoptera and Megaptera ; nevertheless it is strictly defined 

 by the raised membranous fold or " wreathband " {Kranzhand). This circumstance, 

 and that of the baleen-plates and matrix forming two long strips outside, and not 

 merely occupying the anterior midpalatal space, militate against the baleen being the 

 homologue of the Sirenian horny rasping-plate. The above authorities affirm that 

 in the fcetus the subsidiary whalebone-blades " consist each of a fasciculus of hairs 

 agglutinated by the gum;" and as there is no special cortical tissue, this serves as "a 

 sufficient proof that the hairs are the primitive formation of every baleen blade." 

 Hence the conclusion arises that the homologues of the baleen, in the so-called herbi- 

 vorous Cetacea, are the long hairs and bristles found inside the mouth, and situated, like 

 the baleen, lengthwise outside on each side of the palate. 



Eeverting to the structure of the Ruminant mouth (for instance, that of the Sheep), 

 the palate is smooth behind, transversely ridged (or covered by short, double, somewhat 

 V-shaped arches') in front of the molars to as far as the terminal well-known semilunar 

 pad. This last, when seen in front, quite resembles the so-called inner lip of Manatus. 

 The fringed part appears as the homologue of the bruising plate of that genus ; and 

 the posterior part corresponds in each as the smooth portion of the palate. It is true 

 there are no hairs developed within the buccal region in the Sheep, but, instead, 



' In this species also Professor Flower (P. Z. S. 1869, p. 606) has found a fringe of short, stout, coarse fibres 

 or hairs basally and outside the baleen, corresponding with which in the Manatee short hairs and bristles 

 obtain. 



2 Eay Soo. 1866. Translated firom the Danish Eoy. Acad. Mem. 1861 and 1862. 



" Professor Turner (Trans. Eoy. Soc. Ediab. vol. xxvi. p. 222) holds that these palatal folds in Euminants are 

 the equivalent of whalebone. But in the Cetacea we have palatal structures with which they seem more allied ; 

 hence the homologue of the whalebone must be looked for external to them. 



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