jaw, decays and softens away like the old cuticle of the sole of the
foot when steeped in water”(l).
A thin transverse section of baleen, viewed with a low magnifying
power, demonstrates that the coarse fibres, as they seem to
the naked eye, which form the central substance, are hollow tubes(2),
with concentric laminated walls. Wdien a high magnifying power is
applied to such a section, the concentric lines are shown not to be
uniform; but interrupted here and there by minute elliptical dilatations,
which are commonly more opake than the surrounding
substance, and which, like the calcigerous cells of true bone, are
probably remains of the primitive cells of the formative substance:
similar long elliptical opake bodies or cells, are dispersed irregularly
through the straight parallel fibres of the dense outer laminae of the
baleen plate.
The chemical basis of baleen, according to Brande, is albumen
hardened by a small proportion of phosphate of lime.
HYPEROODON.
133. Before leaving the consideration of the horny teeth of
the Mammalia, it seems proper to notice in the present chapter the
hard horny pointed processes which are said to project from the
palate of the Bottle-nose Dolphin, thence called Hyperoodon, by
Lacepede ; which processes may be regarded as analogous to the
baleen-plates in true Whales, but I regret that no opportunity has
occurred to me of examining them.
RYTINA.
134. The singular armature of the palate and lower jaw, in
the Rytina, or Arctic Dugong, likewise falls within the present
category. According to Steller(3), this marine animal has no true
teeth, but only two large whitish dental masses, one adhering to
the palate, the other to the opposed part of the lower jaw : they
are not implanted by gomphosis, but adhere by numerous pores to
corresponding papillae of the membrane covering the palate and
lower jaw; besides which, the palatal tooth is fixed at the sides of
(1) Loc. cit. p. 397- (2) Heusinger Histoiogie, p. 198, pi. ii, fig. 3.
(3) Nova. Comment, Petropolit. tom, ii. p. 294, 1751.
its anterior part to furrows in the lining membrane of the thick lip.
The free surface of the dental mass is sculptured by undulating
grooves and risings, adapted to corresponding inequalities in the
opposite mass.
Dr. Brandt(1) has shown by later and more minute examination
of the problematical teeth of the Rytina, deposited by Steller
in the Petersburgh Collection, that their texture is horny, consisting
of minute hollow fibres, placed vertically to the plane of the grinding
surface of the tooth, but of unusual density. Thus the dentition
of the Rytina closely resembles that of the Ornithorhynchus in both
the texture and implantation of the teeth, which will probably be
found to contain a similar or greater proportion of osseous matter.
M. F. Cuvier(2) has suggested, that the above described plates may
be analogous in position, as in texture, to the horny covering of the
opposed surfaces of the deflected portions of the upper and lower
jaws in the Dugong.
C H A P T E R I II .
TEETH OF BRUTA, (EDENTATA, C d v .)
ORYCTEROPUS.
135.—The Orycterope, or Cape Ant-eater, differs from the
edentulous Ant-eaters of South America, in having teeth in both
jaws(3). These teeth are of a simple form, but peculiar structure;
their common number in the mature animal is |^ = 26 ; they all
belong to the molar series. The anterior teeth are very small, and
are not unfrequently wanting, or are concealed by the gum, especially
the first in the upper jaw : the second tooth of the upper jaw is
small, compressed and obtuse ; it opposes a similar one in the
lower jaw : the third and fourth molars increase in size, have an
elliptical transverse section, and a triturating surface of two lacets :
the fourth and fifth molars are the largest in the upper jaw1, are
of equal size, and have a longitudinal depression in their internal
(1) Mém. de 1’Acad. Imp : de Pétersb. vi. ser. t. ii. p. 103.
(2) Histoire des Cétacés, 8vo. 1830 p. 730, (3) PI. 70, fig. 89.