The series of skulls of _Z. grebnitzkii_, which the Museum owes to the
activities of Dr. L. Stejneger and Mr. N. Grebnitzki, comprises specimens
of different ages, and, as will be shown presently, probably both sexes.
Taken together with the skulls from the east coast of the United States
they probably represent very fully the variations which the skull
undergoes in the present species. These changes may, perhaps, be best
made evident by the following brief descriptions of the various skulls:
_21975. Charleston, South Carolina._—Young female. (Type of _Z.
semijunctus_.) All sutures open, and elements of occipital bone
distinguishable. No mesethmoid ossification. Opposite maxillary notches,
premaxillæ closely approximated, nearly flat and horizontal, and about
level with adjacent parts of maxillæ. Left premaxilla grooved
longitudinally at this point. Orifice of anterior nares on a level with
lower end of rectangular projecting boss formed by superior portion of
nasals. Rostrum pointed, much broader distally than it is deep. A very
distinct rudimentary alveolar groove in distal end of each maxilla.
Proximal end of vomer resting against anterior face of nasals and
reaching up to overhanging boss. Anterior face of the latter nearly flat.
(Pl. 14, fig. 1; pl. 18, fig. 1; pl. 20, fig. 1; pl. 21, fig. 2.)
Rami of mandible not anchylosed together at symphysis. Teeth hollow, open
at the root, acute at apex, tipped with enamel; diameter 10 mm. (Pl. 22,
fig. 1; pl. 24, fig. 1.)
_20971. Barnegat City, New Jersey._—Adult female. Majority of sutures
open, but those on superior surface of rostrum between maxillæ and
premaxillæ partly anchylosed. Vomer nearly all anchylosed to rostral
portion of premaxillæ; it presents a slight median elevation, but there
is no mesirostral ossification. Right premaxilla in front of nares broad,
flat, and horizontal; left, nearly so, but with a quite broad
longitudinal groove. Opposite maxillary notches premaxillæ nearly on a
level with adjacent parts. Orifice of anterior nares level with lower end
of nasal boss. End of rostrum quite acute, and broader than deep.
Rudimentary alveolar groove distinct distally. Proximal end of vomer
anchylosed with anterior face of nasals and reaching up to nasal boss,
which has a sharp median ridge completing nasal septum superiorly.
Anterior face of nasal boss slightly concave on each side of median line.
(Pl. 14, fig. 2; pl. 18, fig. 2; pl. 20, fig. 2; pl. 21, fig. 3.)
Rami of mandible anchylosed together at symphysis and suture largely
obliterated. Teeth slender, cylindrical, rugose, rather blunt; roots
closed; diameter 13 mm. (Pl. 24, fig. 3.)
_22069. Bering Island._—Adult female? All the sutures about as in
preceding specimen. Mesirostral ossification distinct, rounded, extending
from base of rostrum nearly to apex, but disappearing before reaching
line of anterior ends of maxillæ. Its upper surface below that of
premaxillæ. Premaxillæ approximated, and right premaxilla with an angular
process near base of rostrum overlapping mesirostral ossification.
Premaxillæ at base of rostrum, anterior nares, proximal end of vomer, and
nasals as in preceding skull. Apex of rostrum moderately acute, broader
than deep. Rudimentary alveolar groove shallow. (Pl. 15, fig. 1.)
Rami of mandible anchylosed together and suture largely obliterated.
Teeth somewhat fusiform, blunt; roots closed; diameter, 14 mm. (Pl. 22,
fig. 3.)
_83991. Bering Island._—Similar in all respects to preceding, but
mesirostral ossification a little less well developed.
_22874. Bering Island._—Entirely similar to two preceding, but premaxillæ
a little curved out from mesirostral ossification and left premaxilla
opposite maxillary notch rather strongly inclined, nearly vertical.
Anterior face of nasal boss distinctly concave. (Skull defective.)
_21246. Bering Island._—Sutures as in three preceding skulls. Mesirostral
ossification distinct and rounded, but much below level of premaxillæ.
Rostral portion of premaxillæ narrow and widely divergent toward base of
rostrum, leaving mesirostral entirely exposed. Right premaxilla on a line
with maxillary notches strongly concave and sunk below level of maxillæ.
Left premaxilla vertical, with a broad groove. Right premaxilla remains
low and concave proximally, the posterior end being then abruptly turned
upward and reaching level of vertex. Orifice of anterior nares on a level
with lower end of nasal boss, and vomer resting against anterior face of
nasals, which latter have a median ridge continuing nasal septum, but
with a slight vacuity between the two. Rudimentary alveolar groove nearly
obliterated. Outer sides of premaxillæ at distal end strongly concave.
Rostrum rather acute, about as deep as wide opposite distal ends of
maxillæ. (Pl. 15, fig. 2.)
_20993. Bering Island._—Adult male? (Type of _Z. grebnitzkii_). Majority
of sutures open, but maxillæ and premaxillæ anchylosed together above and
on the sides. Premaxillæ approximated anteriorly, but diverging
posteriorly. Mesirostral ossification well developed, reaching level of
premaxillæ; anteriorly rather narrow but a little broader near middle of
rostrum, where it is beveled off abruptly. Behind this point premaxillæ
strongly concave, nearly vertical and widely separated, forming a large
and deep basin, in the bottom of which the vomer appears as a broad,
irregular bony surface. Bottom of basin much below level of surrounding
parts. Orifice of anterior nares much below level of nasal boss. Vomer
reaching lower end of nasals. Anterior face of latter strongly concave,
with only a moderate median ridge completing nasal septum above.
Mesirostral with a median groove at distal end. Premaxillæ high at distal
end, but sides nearly plane. Rostrum compressed near apex, deeper than
wide. (Pl. 16, fig. 1; pl. 19, fig. 1; pl. 20, fig. 3.)
Rami of mandible anchylosed together and suture partly obliterated. Teeth
conical, with rather short, acute tips; roots closed, short and conical;
diameter, 25 mm. (Pl. 23, fig. 1; pl. 24, fig. 2.)
_21245. Bering Island._—Nearly all sutures between maxillæ and premaxillæ
at end of rostrum, above and below, anchylosed together, but majority of
others traceable. Condition of superior surface of skull very similar to
that of preceding, but premaxillæ rather low at distal end. Mesirostral
at distal end rather lower than premaxillæ and concave superiorly; more
posteriorly assuming form of a narrow ridge, with a deep channel between
it and premaxillæ on each side. More posteriorly still it widens rapidly,
with a convex surface, and terminates abruptly with a truncated end, the
surface of which is concave. A deep basin around nares, as in preceding
skull. Orifice of anterior nares far below level of nasal boss. The
latter largely absorbed and deeply undercut and concave in front. Nasal
septum terminating before reaching lower end of nasals, and ridge on
latter low and traversing left nasal. Sides of premaxillæ at distal end
very concave. Rudimentary alveolar groove nearly obsolete. Rostrum blunt
at apex, and about as deep as wide at anterior ends of maxillæ. (Pl. 16,
fig. 2.)
_21248. Bering Island._—Similar to preceding, but mesirostral
ossification higher than premaxillæ at distal end and convex above; less
abruptly widened posteriorly and posterior termination flat. Narrow, deep
grooves between ossification and premaxillæ on each side, or, in other
words, premaxillæ more closely approximated to sides of mesirostral
distally. Basin around nares and conformation of the several bones
bordering it similar to preceding. Sides of premaxillæ concave at distal
end, the grooves thus formed in them intruding some what on the maxillæ,
especially posteriorly. Apex of rostrum very blunt, rounded off below and
projecting above; deeper than wide. Rudimentary alveolar groove nearly
obsolete. (Pl. 17, fig. 1; pl. 22, fig. 4.)
Rami of mandible anchylosed together and the symphysis and suture largely
obliterated. Teeth very broadly fusiform; tip short and rather blunt;
roots closed; diameter 30 mm.
_49599. Newport, Rhode Island._—Adult male. All sutures on superior
surface of skull more or less anchylosed together. Mesirostral
ossification and premaxillæ all on one level near apex of rostrum, but at
extreme tip mesirostral lower, forming a narrow ridge with a deep groove
on each side between it and premaxillæ. The same conformation repeated
more posteriorly, but grooves deeper and wider, while mesirostral
maintains the same level as premaxillæ. It widens suddenly here, forming
a broad flat-topped mass, which is a little overlapped by the premaxillæ.
The mass terminates suddenly somewhat behind middle of rostrum with a
deep concavity placed obliquely. Basin in front of the nares and
conformation of bones composing it as in two preceding skulls. Vomer at
proximal end touching lower end of nasals, and nasal septum continued
behind and above it as a low ridge, composed of the inner edges of the
two nasal bones and reaching up to the nasal boss. Outer sides of
premaxillæ near distal end deeply concave. Apex of rostrum rather blunt,
deeper than wide opposite distal ends of maxillæ; all the bones
anchylosed together, but some of the sutures indicated by grooves.
Rudimentary alveolar groove nearly obsolete. (Pl. 17, fig. 2; pl. 19,
fig. 2; pl. 21, figs. 1, 5.)
Rami of mandible anchylosed together at symphysis, the suture indicated
only by a groove. Teeth large, broadly conical and tapering at the tip.
Root very short, rugose, conical and closed; diameter 29 _mm._ (Pl. 22,
fig. 2; pl. 23, figs. 2, 3.)
The dimensions of the several skulls are as follows:
_Dimensions of ten skulls of Ziphius cavirostris (including the types
of Z. grebnitzkii Stejneger and Z. semijunctus Cope)._
Column headings:
A: 83991. Bering Island. _grebnitzkii._
B: 21248. Bering Island. _grebnitzkii._
C: 22874. Bering Island. _grebnitzkii._
D: 21246. Bering Island. _grebnitzkii._
E: 20993. Bering Island. Type _grebnitzkii_.
F: 22069. Bering Island. _grebnitzkii._
G: 21245. Bering Island. _grebnitzkii._
H: 21975. Type _semijunctus_.
I: 20971. Barnegat, N. J. Female, _cavirostris_.
J: 49599. Newport, R. I. Male, _cavirostris_.
Measurements. A B C D E F G H I J
mm. mm. mm. mm. mm. mm. mm. mm. mm. mm.
Total length 900 877 [a]807 850 963 882 855 797 945 915
Length of rostrum 491 480 [a]397 470 550 480 476 463 550 514
Height from vertex to 433 450 ... ... 515 471 481 349 440 465
inferior border of
pterygoids
Distance from tip of rostrum 664 670 ... ... 735 682 673 614 735 726
to posterior free margin of
pterygoids (median)
Distance from the same to 617 621 [a]538 600 690 623 589 590 708 676
anterior end of nasals
Breadth between centers of 495 513 [b]499 488 563 [b]486 492 393 476 530
orbits
Breadth between zygomatic 511 513 ... 505 573 531 530 415 503 548
processes
Breadth between temporal fossæ 270 309 325 300 349 317 311 242 302 313
Breadth of rostrum at base 319 331 345 324 380 337 320 249 307 337
Breadth of rostrum at middle 102 117 [b]94± 107 120 109 112 83 112 113
Breadth of premaxillæ at same 54 67 58 62 78 70 75 44 62 80
point
Depth of rostrum at middle 66 81 80 79 118 117 113 50 77 107
Breadth of premaxillæ in 176 177 184 205 221 230 219 128 176 234
front of nares
Greatest breadth of anterior 74 77 77 90 98 103 108 70 76 112
nares[c]
Greatest length of temporal 161 158 154 149 152 140 146 133 143 155
fossa
Greatest depth of temporal 81 73 77 79 87 74 89 67 80 76
fossa
Length of orbit (ant.-post.) 131 133 132 130 137 126 117 113 134 132
Distance from anterior end of 78 92 82 70 83 89 85 61 82 99
orbit to maxillary notch
Length of tympanic bulla ... ... ... ... 53 ... ... 54 ... 55
Breadth of tympanic bulla ... ... ... ... 24 ... ... 37? ... 25
Length of mandible ... 769 ... ... ... ... ... 679 ... 842
Length of symphysis ... 170 ... ... ... 184 ... 149 ... 176
Depth of mandible at coronoid ... 153 ... ... ... ... ... 133 ... 153
[a] About 150 mm. lacking from end of beak.
[b] A little abraded.
[c] Taken on a level with the curve of the inner margin of the
premaxillæ. Is only approximate.