The teeth are remarkable for their size and form. They are somewhat more
than twice as broad as teeth of adult males of _bidens_, as shown by the
figures of Lankester[32] and Grieg,[33] and also a little longer. They
are, in fact, probably broader than, or at least as broad as, the teeth
of any other species of _Mesoplodon_, not excepting _layardi_. Sir
William Turner remarks regarding a specimen of _layardi_ examined by him
that “the breadth of the tooth, where it emerged from the alveolus, was
3½ inches.”[34] He does not state, however, whether the measurement was
taken along the top of the alveolus, at an angle with the transverse axis
of the tooth, or along the transverse axis itself. At all events, the
teeth figured by Owen and others are much less than 3½ inches broad. The
teeth of adult _europæus_ are only 2 inches broad, and of _bidens_, as
already stated, 1½ inches broad.
In _stejnegeri_ (Pl. 12, figs. 1-3) the portion of the tooth above the
alveolus is inclined slightly inward and backward, but the pointed tip
curves outward so as to be vertical. When extracted from the alveolus,
the whole tooth is found to be concave internally and convex externally.
The posterior margin is convex and the anterior sinuous, a slight
convexity occurring on the portion which projects above the alveolus. In
this place the outer coating of cement is broken through, showing the
underlying dentine or osteo-dentine, which is somewhat corroded or
absorbed. This is particularly noticeable on the left tooth.
The upper margin of the tooth is transverse, or nearly at right angles
with the anterior and posterior margins. The posterior angle is rounded
and the anterior raised into an acute point by the projection of the
dentine as a distinct, sharp cusp. The inferior end of the tooth is cut
off obliquely and the margin is broken by numerous prominent rugosities.
The surface of all that part of the tooth which is contained in the
alveolus and covered by the gum above it is rugose, while the part above
the gum is quite smooth and highly polished.
The right tooth has the following dimensions (in straight lines): Length
of anterior border, 150 mm.; length of posterior border, 107; length of
superior border, 54; length of inferior border, 86; average length of
exposed dentine tip, 10; greatest breadth of tooth, antero-posteriorly,
81; greatest breadth of tooth, transversely, 15; distance from center of
base of exposed portion, when in position in the alveolus, to tip of
dentine projection, 82; distance from center of base of portion above the
gum to tip of dentine projection, 70; distance from center of base of
portion above the gum to center of inferior margin, 76.
The dimensions of the skulls are as follows, those of the type-specimen
having been revised and corrected:
_Dimensions of two skulls of M. stejnegeri._
Column headings:
A: 143132 U.S.N.M. Yaquina Bay, Oregon, adult.
B: 21112 U.S.N.M. Bering Id. Type (1715), young.
Measurements. A B
Total length 715 [a]633
Length of rostrum 413 [a]325
Distance from occipital condyles to distal end of 612 567
maxillæ
Breadth between centers of orbits 309 279
Breadth between zygomatic processes 310 278
Breadth between temporal fossæ 228 212
Breadth between postorbital processes of frontals 323 ...
Breadth of rostrum at base (between maxillary 172 [b]158
notches)
Breadth of rostrum at middle 40 44
Depth of rostrum at middle 52 42+
Greatest breadth of anterior nares 56 54
Greatest breadth of premaxillæ proximally 130 118
Greatest breadth of premaxillæ in front of nares 108 109
Length of temporal fossa 92 86
Depth of temporal fossa 63 46
Antero-posterior length of orbit 96 82
Breadth of foramen magnum 38 39
Length of tympanic bulla 48 ...
Breadth of tympanic bulla 32 ...
Length of mandible 610 ...
Length of symphysis 138 ...
Distance from anterior end of mandible to alveolus 166 ...
[a] Tip of rostrum lacking.
[b] The skull is much worn around the left notch and the measurement is
only approximate.