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._ Column headings: A: Greatest height. B: Greatest breadth. Species and locality. Sex and Length. Large Small Remarks. age. tooth. tooth. A B A B _B. arnuxii._ ft. in. mm. mm. mm. mm. Akaroa (Van Beneden. Male. 32 0 [a]90 90 66 40 From Type). figure.[b] New Brighton (Haast Male(?). 30 6 [a]73 63 47 31 From and Flower). figure. Port Nicholson (Knox (?) 27 0 [a]65 50 (?) (?) From and Hector). figure. Locality unknown (Van (?) (?) 72 53 51 30 From Beneden and Gervais, figure. pl. 21 _bis_). _B. bairdii._ 49725—Centerville, Male(?), 41 ± [a]83 65 53 28 California. adult. 49726—St. George Female, 40 5 [c]79 72 62 45 Island. adult. 49727—St. George Male, im. 25 0 [a]86 61 ... ... Island. 142118—Bering Island Young. ... ... [a]50 37 31 31 [a] Tip more or less acute. [b] Van Beneden’s measurements are slightly different. [c] Tip much worn. A description of the teeth of the different specimens of _B. bairdii_ is subjoined.