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?).

ABCDEFGH
mm.mm.mm.mm.mm.mm.mm.mm.
Total length of skull1,3721,392b1,1741,5241,4231,3781,062(?)1,474
Height from vertex to inferior border of pterygoids533494(?)493563544......575
Breadth across middle of orbitsc625684577766682662530[716]
Breadth across postorbital processes686748606808722...560[760]
Breadth across zygomatic processes671748584750675...520[740]
Length of rostrum919894800960925880578+1,025
Breadth of rostrum at base399414378475420428310429
Breadth of rostrum at middled152150149207197188...223
Length of premaxillæ.........................
Breadth of premaxillæ at middled9190101120119115...125
Greatest breadth of premaxillæ in front of nares208210189235217238187239
Greatest breadth of premaxillæ behind nares...246193215195181165197
Distance from anterior end of premaxillæ posterior end of pterygoids (median)1,0971,0809351,1851,130...720+1,187
Distance from anterior end of premaxillæ to anterior end of vomer345264252276270260115+307
Length of portion of vomer visible on palate...420253±535370472360±450
Length of nasals (greatest, median, straight)132162(?)13413511813598142
Breadth of nasals (greatest)1021801251199710590105
Breadth of anterior nares7410280110989683100
Breadth of foramen magnum61...728582848371
Breadth across occipital condyles191213186261228240195235
Breadth of each condyle......751231041088398
Height of each condyle......135193171168142178
Length of mandiblee1,2451,236...1,3341,2891,282f8831,360
Length of symphysis310294...295295270f145310
Height at coronoid211222...271230223175245
Distance from tip of jaw to center of first tooth3445...504835f2260
Distance from tip of jaw to center of second tooth155159...200182165f87195

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.

EARBONES.

The tympanic and periotic bones of B. bairdii (Pls. [34]-[37]) present a number of characters by which they may be distinguished from those of B. arnuxii. While of about the same size in both species, the two bones when in the natural position, viewed from without, are nearly square rather than triangular in outline in B. bairdii, the superior border of the periotic being nearly parallel with the inferior border of the tympanic, and the anterior lobe of the periotic being turned down nearly at right angles with the rest of the bone. The periotic is shorter anteriorly than the tympanic in B. bairdii, while the reverse is true in B. arnuxii. In the former species the eustachian canal of the tympanic is wider, the distance between the outer and inner lips being greater. The involuted portion of the inner lip is shorter and differently shaped. The groove between the postero-inferior lobes is wider. The periotic beside having a much shorter anterior lobe than in B. arnuxii has also a smaller and smoother middle lobe, and the internal auditory meatus is smaller and more oblique. The dimensions of the bones in the Centerville beach skull, No. 49725, are as follows: Tympanic: greatest length, 62 mm.; greatest breadth, 46; least breadth of eustachian canal, 17; height at sigmoid process, 47. Periotic: greatest length, 66; greatest breadth, 40; height at center of middle lobe, 35; length from tip of anterior lobe to anterior margin of internal meatus, 38.

TEETH.

Although all the specimens of Berardius bairdii are more or less incomplete, two or three of the mandibular teeth have been preserved in nearly every instance; namely, in the adult female from St. George Island, the left anterior and right and left posterior; in the immature male from the same island, both anterior teeth; in the Centerville beach specimen, the left anterior and right (?) posterior teeth; in the skull from Bering Island formerly regarded as the type, all four teeth; in the very young skull from Bering Island, the left anterior and posterior teeth.

Taken as a whole, these teeth are not larger than those found in the specimens of B. arnuxii thus far recorded, but in both species they vary so much on account of age, or for other reasons, that a comparison of dimensions is unsatisfactory. The dimensions are as follows:

Dimensions of teeth of Berardius arnuxii and B. bairdii.