External dimensions of Berardius bairdii and B. arnuxii.
Column Headings: bairdii. A: 49726 St. George Island, Alaska, (Judge), female adult. B: 49727 St. George Island, Alaska, (Judge), male imm. arnuxii. C: Wellington, New Zealand, (Hector), male.
| Measurements. | A | B | C | |||
|---|---|---|---|---|---|---|
| ft. | in. | ft. | in. | ft. | in. | |
| Total length | 40 | 2 | 25 | 5 | 27 | 6 |
| per cent. | per cent. | per cent. | ||||
| Distance from tip of snout to blowhole | 10.8 | 11.8 | 12.8 | |||
| Distance from tip of mandible to corner of mouth | 6.0 | 6.9 | a6.1 | |||
| Breadth of flukes from tip to tip | 25.3 | 24.6 | 19.1 | |||
| Length of pectoral fin along outer edge | 12.4 | 13.4 | 9.4 | |||
| Distance from anus to “end of body” | 29.0 | 29.8 | [34.0] | |||
| Height of dorsal fin | 2.5 | 2.4 | 3.0 | |||
| Distance from anterior base of dorsal fin to “end of body” | 29.7 | 29.2 | [34.6] | |||
a “Length of gape.”
The measurements of these specimens of bairdii agree well together. The specimen of arnuxii appears to have had narrower flukes, shorter pectoral fin, and a rather higher dorsal fin, situated farther forward than in bairdii. Measurements of a larger number of specimens might show that some or all of these differences of proportion are elusive, but it will be observed that in the Wellington specimen of arnuxii, recorded by Doctor Haast, the breadth of the flukes is only 21 per cent of the total length. The pectoral fin is said to be only 19 inches long, or only 5.2 per cent of the total length, but the manner of taking the measurement is not mentioned.
As regards size, the largest specimen of B. arnuxii of which I find record is the type specimen. This was 32 feet long, and the skull 1,400 mm., or about 55 inches long. This appears to have been an adult male. The Centerville specimen of bairdii, which was an adult male, was about 41 feet long, and the skull 1,532 mm., or about 60 inches long, while the adult female from St. George Island was 40 feet 2 inches long and the skull 56 inches. Although the total length of the specimens of bairdii is so much greater, it will be observed that the length of the skull, while a little greater, absolutely fails to measure up to the proportions found in arnuxii. It might be suspected on this account that the external measurements of bairdii were exaggerated, but that such is not the case will appear from an examination of the measurements of vertebræ given on page 75. It is evident that the specimens of bairdii are far more massive in all parts of the skeleton than the specimen of arnuxii there cited. The same relations will be found upon comparing measurements of the specimen of arnuxii figured by Van Beneden and Gervais.[57] The truth appears to be that bairdii is a much larger species, but that the skull is considerably smaller relatively.
SKULL.
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.