The skull of _Berardius bairdii_ presents many characters by which it may
be distinguished from that of _arnuxii_, whether adult or young. As
compared with the latter, the rostrum is less massive at the base. The
pterygoid has a rounded extension posteriorly and superiorly, so that the
posterior portion of the upper border of the pterygoid sinus is convex,
rather than nearly straight, as in _arnuxii_. The exoccipital is larger
and broader distally below, and its external surface is plane or concave,
rather than convex, as in _arnuxii_. The distal end of the zygomatic
process is much more incurved. The nasal bones instead of presenting
lateral extensions have nearly straight sides. The vomer is deeply
emarginate at the base of the skull posteriorly where it rests against
the presphenoid. The palatines extend scarcely or not at all in front of
the pterygoids. The foregoing differences will readily be seen by
comparing the figures on Pls. 26-29 with those of the type of _B.
arnuxii_ given in Van Beneden and Gervais’s Osteography, plate 23.
The following are dimensions of skulls of both species:
_Dimensions of five skulls of Berardius bairdii (including the type)
and of three skulls of B. arnuxii._
Column headings:
_B. arnuxii._
A: New Brighton, New Zealand (Flower). No. 3.
B: New Zealand (V. B. and Gerv.). (Type). ([a])
C: 21511, U.S.N.M., New Zealand, young.
_B. bairdii._
D: 49726, St. George Island, female, adult.
E: 49725, Centerville, California, male(?) adult.
F: 20992, Bering Island, (Type).
G: 49727, St. George Island, male, young.
H: Mounted skull, Bering Island(?) (Grebnitzki?).
A B C D E F G H
mm. mm. mm. mm. mm. mm. mm. mm.
Total length of 1,372 1,392 [b]1,174 1,524 1,423 1,378 1,062(?) 1,474
skull
Height from vertex 533 494(?) 493 563 544 ... ... 575
to inferior
border of
pterygoids
Breadth across [c]625 684 577 766 682 662 530 [716]
middle of orbits
Breadth across 686 748 606 808 722 ... 560 [760]
postorbital
processes
Breadth across 671 748 584 750 675 ... 520 [740]
zygomatic
processes
Length of rostrum 919 894 800 960 925 880 578+ 1,025
Breadth of rostrum 399 414 378 475 420 428 310 429
at base
Breadth of rostrum 152 150 149 207 197 188 ... 223
at middle[d]
Length of premaxillæ ... .... ... ... ... ... ... ...
Breadth of 91 90 101 120 119 115 ... 125
premaxillæ at
middle[d]
Greatest breadth of 208 210 189 235 217 238 187 239
premaxillæ in
front of nares
Greatest breadth of ... 246 193 215 195 181 165 197
premaxillæ behind
nares
Distance from 1,097 1,080 935 1,185 1,130 ... 720+ 1,187
anterior end of
premaxillæ
posterior end of
pterygoids
(median)
Distance from 345 264 252 276 270 260 115+ 307
anterior end of
premaxillæ to
anterior end of
vomer
Length of portion ... 420 253± 535 370 472 360± 450
of vomer visible
on palate
Length of nasals 132 162(?) 134 135 118 135 98 142
(greatest,
median, straight)
Breadth of nasals 102 180 125 119 97 105 90 105
(greatest)
Breadth of anterior 74 102 80 110 98 96 83 100
nares
Breadth of foramen 61 ... 72 85 82 84 83 71
magnum
Breadth across 191 213 186 261 228 240 195 235
occipital condyles
Breadth of each ... ... 75 123 104 108 83 98
condyle
Height of each ... ... 135 193 171 168 142 178
condyle
Length of mandible [e]1,245 1,236 ... 1,334 1,289 1,282 [f]883 1,360
Length of symphysis 310 294 ... 295 295 270 [f]145 310
Height at coronoid 211 222 ... 271 230 223 175 245
Distance from tip 34 45 ... 50 48 35 [f]22 60
of jaw to center
of first tooth
Distance from tip 155 159 ... 200 182 165 [f]87 195
of jaw to center
of second tooth
[a] From Van Beneden and Gervais figure.
[b] A little broken at tip.
[c] “Suprafrontal processes of maxillæ.”
[d] Same point.
[e] “Length of ramus.”
[f] About 27 mm. lacking from tip of mandible.
The foregoing measurements indicate a considerable variation in
proportions among the different individuals, but there appears to be
nothing that can be fixed upon in this small series to distinguish the
two species by dimensions alone.