In B. bairdii the anterior border of the scapula is narrower than in B. arnuxii, the anterior ridge coming close to it and lying parallel with it. The acromion is directed more upward, so that the angle between it and the body of the scapula is more acute, and the process itself is rather more expanded distally. The coronoid is inclined a little more downward. The whole surface of the scapula is very uneven. ([Pl. 33], fig. 2.)
HUMERUS AND ULNA.
The humerus is shorter than in B. arnuxii and broader distally, and much more recurved on the ulnar side. The ulna is much broader distally and its whole shape is different. ([Pl. 33], figs. 3 and 4.)
CHEVRONS.
As the skeleton of the typical form arnuxii has been described in considerable detail and accurately figured by Flower and by Van Beneden and Gervais, it is not considered necessary to give a complete description of that of bairdii in this place. The entire skeleton and many of the separate bones are figured in Pls. [42], [32], and [33]. The phalanges are lacking altogether, or are incompletely represented, in the various skeletons of bairdii, and for that reason the phalangeal formula can not be given. The chevrons number ten in the skeleton from Centerville beach, California (Cat. No. 49725). Both Flower and Van Beneden and Gervais give nine chevrons as the number for the skeleton of arnuxii in the Hunterian Museum, London, but the latter authors have added a tenth in outline in the figure of the skeleton of that species which is in the Paris Museum. Ten are mentioned by Hector as the correct number for the skeleton of arnuxii from Wellington Harbor examined by him.[61]
STERNUM.
The sternum of bairdii ([Pl. 32], fig. 2) consists of five segments and does not offer characters by which to distinguish it from that of arnuxii. In the former species the first eight pairs of ribs possess distinct heads and tubercles; the tubercle is rudimentary in the ninth pair and absent in the tenth and eleventh.
The dimensions of the three skeletons of bairdii and of that of arnuxii described by Flower are as follows:
Dimensions of one skeleton of Berardius arnuxii and three skeletons of B. bairdii.
Column Headings: B. arnuxii. B: New Brighton, New Zealand, 1868, (Flower). No. 3. B. bairdii. C: 49726 St. George Island, Alaska, female adult. D: 49725 Centerville, California, male(?) adult. E: 49727 St. George Island, Alaska, male young.