The teeth of the various North Atlantic and North Pacific specimens merit
a somewhat more detailed description than is given on pages 50 to 53. Six
pairs of teeth from six different individuals are available for
comparison. Their dimensions are as follows:
_Dimensions of the teeth of Ziphius cavirostris._
Cat. Locality. Age. Sex. Teeth.
No.
Length. Greatest
diameter.
mm. mm.
21975 Charleston, South Carolina[a] Young Female 45 10
20971 Barnegat City, New Jersey Adult Female 56 13
22069 Bering Island Adult (Female?) 41 14
20993 do[b] Adult (Male?) 48 25
21248 do Adult (Male?) 58 30
49599 Newport, Rhode Island Adult Male 63 29
[a] Type of _Z. semijunctus_.
[b] Type of _Z. grebnitzkii_.
_21975. Charleston, South Carolina._—Young female. (Type of _Z.
semijunctus_.) The teeth are slender, conical, and acuminate, largest at
the base and tipped for about 2 mm. with white enamel. The remainder of
the teeth is coated with a thin layer of cement. The teeth in what
appears to be their natural position protrude horizontally from the
mandible for about 17 mm. They are slightly curved upward near the tip
and are oval, or elliptical, in section, the transverse diameter being a
little less than the vertical diameter. They are a little flattened
externally. The surface is smooth. They are open at the root, and hollow.
(Pl. 38, figs. 1, 2; pl. 22, fig. 1.)
Doctor Manigault, curator of the Charleston Museum, wrote to Professor
Cope regarding these teeth, as follows:
Another peculiarity of the head consists in the lower maxillary bones
being provided each at its point with a single small and very sharp
tooth. These were not noticed during the dissection, owing to their
being too much embedded in the integuments.[46]
_20971. Barnegat City, New Jersey._—Adult female. The teeth are slender,
cylindrical, and irregularly pointed at both ends. The tips show what
appears to be an inner core of dentine which has been worn down nearly to
the cement coating and somewhat fractured. The cement coating is several
millimeters thick, but does not increase the diameter of the teeth near
the middle, so that they remain irregularly cylindrical throughout. The
surface of the cement is rough and irregular. The root is short, conical,
and closed at the end. These teeth are nearly straight. As they have been
extracted from the jaw and the latter is broken it is not possible to
distinguish which is the upper and which the lower surface, but they are
irregularly oval in section, and a little compressed. (Pl. 38, figs.
3-5.)
In my original notes on this specimen, I recorded that there was a small
pair of teeth behind the larger ones described above. Mention of these
will be made again later. (See p. 57.)
_22069. Bering Island._—Adult female (?). The teeth are in position in
this specimen and are nearly horizontal in position, but a little
inclined upward and toward each other. They do not extend beyond the tip
of the jaw nor up to the level of the upper surface of the symphysis, but
protrude about 13 mm. beyond the alveoli on the side. They are rather
slender, somewhat fusiform, blunt at both ends and slightly curved
upward. The surface is irregular. They are nearly round in section. The
root is closed, and the apex shows what appears to be a core of dentine
surrounded by cement. There is a depression on the inner side near the
root. These teeth are remarkable as intermediate in form between those of
the preceding specimen and those of the specimens next to be mentioned.
(Pl. 38, figs. 6, 7; pl. 22, fig. 3.)
_20993. Bering Island._—Adult male (?). (Type of _Z. grebnitzkii_.) These
teeth are almond-shaped and very symmetrical. They are thickest near the
base and taper gradually to the tip, which is quite acute. They are
somewhat compressed and hence elliptical in section, the vertical
diameter being greater than the transverse diameter. One side (probably
the inner) is flattened. They are slightly curved upward toward the apex,
which is a little worn and fractured. The root is very short and conical.
It is nearly closed, but a very small canal extends upward for about 10
mm. The surface of the tooth is quite smooth, but dull in the lower half.
The line of demarcation between cement and dentine is not evident. (Pl.
38, figs. 8, 9; pl. 23, fig. 1.)
_21248. Bering Island._—Adult male (?). In this specimen the teeth are
still in the natural position in the jaw. They are held in place by
ligaments and protrude far beyond the alveoli, only about one-ninth of
their length being below the superior border. They incline forward at an
angle of about 45° with the longitudinal axis of the jaw and diverge
slightly at the tips.
The teeth themselves have the same general form as those of the preceding
specimen, but are larger. The inner surface is flattened and the outer
strongly convex. The tips are quite pointed, but show some indications of
wear. The roots can not be seen distinctly, but appear to be closed. (Pl.
22, fig. 4.)
_49599. Newport, Rhode Island._—Adult male. These teeth are longer than
those of the preceding specimen, and while they resemble the latter in
general form, taper much more gradually to the tip. The root, or portion
below the point of maximum girth, is much shorter than that above, and
rugose, with several deep furrows. A very small circular opening at the
base of the root marks the orifice of the nerve. The upper half of the
teeth is smooth, and the tips slightly worn and fractured. The small
elliptical worn area is situated on the convex side of the tooth, which
appears to be the outer side. As the alveoli of the jaw are, however,
filled with a network of bone, the teeth can not be inserted in them.
They were detached when received. (Pl. 38, figs. 10, 11; pl. 22, fig. 2;
pl. 23, figs. 2, 3.)
Besides the difference in the size and form of the teeth in the two
sexes, it is probable, as will be seen by consulting the foregoing data,
that in the female the apex of the teeth does not extend more than a very
small distance above the alveoli even in mature individuals, and probably
often not more than a few millimeters; while in adult males the teeth are
almost entirely protruded from the alveoli, which are filled with a
coarse bony network. These differences are carried out in all the
American specimens, and also characterized the New Zealand specimens, as
may be learned from the accounts of Haast and Hector.
A number of rudimentary teeth in addition to the large terminal pair have
been noted in the Aresquiers, Buenos Ayres, and perhaps other specimens,
and two such teeth were found in the mandible of the Barnegat specimen,
behind the large pair. One of these rudimentary teeth has been preserved.
It is cylindrical and moderately curved. The length is 16 mm. and the
diameter 2 mm. The whole tooth, with the exception of the extreme tip, is
thickly coated with cement. The root is closed and the crown acute and
apparently abraded by use. (Pl. 38, fig. 5.)
Returning now to the question of the validity of _grebnitzkii_ as a
species, I would say that after comparing the measurements of the Bering
Island skulls with those of the Atlantic coast specimens, and comparing
the skulls themselves, I have been unable to find any constant difference
of importance, except the size and form of the periotic bone. As the
earbones are lacking from many of the skulls, the series available for
comparison is small.
As compared with the Atlantic coast specimens, the anterior portion of
the periotic bone in _grebnitzkii_ is larger, broader, and more
rectangular in outline when viewed from below. I observe, however, that
the absolute size and outline of the periotic vary considerably in the
different specimens of _grebnitzkii_ without relation to age. The same
appears to be true of _cavirostris_, but comparing the two series of
skulls as a whole it appears to be true that the anterior mass of the
periotic is larger in _grebnitzkii_. I do not think, however, that the
latter species should be kept distinct on this account alone, at least
until the character has been confirmed, and perhaps strengthened by
others, through the examination of a larger series of specimens.