168 DR. J. MURIE ON THE FORM AND STRUCTURE 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 Rorqual (Physalus antiquorum) 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 front. 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 Reinhardt’, 
that in the feetal and very young Balena 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 Balenoptera and Megaptera; nevertheless it is strictly defined 
by the raised membranous fold or “ wreathband” (Aranzband). 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 foetus 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. 
Reverting 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 M/anatus. 
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, 
1 Tn this species also Professor Flower (P. Z. 8. 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. 
? Ray Soc. 1866. Translated from the Danish Roy. Acad. Mem. 1861 and 1862. 
* Professor Turner (Trans. Roy. Soc. Edinb, vol. xxvi. p. 222) holds that these palatal folds in Ruminants 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. 
