[52]At the time this was written it was not known that there were really four teeth in the lower jaw, but it is interesting to note that when the mandible was covered by the integuments none of the teeth was visible in the male, although the individual was 25 feet long, and that only two teeth were visible in the adult female. [53]Proc. U. S. Nat. Mus., vol. 6, pp. 75-77, June 22, 1883. [54]Duvernoy, Ann. Sci. Nat., ser. 3, Zoöl., vol. 15, 1851, p. 52, footnote. [55]Ann. Mag. Nat. Hist., ser. 4, vol. 6, October, 1870, p. 348. [56]Trans. New Zealand Inst., vol. 10, 1878, p. 338. [57]Ostéographie des Cétacés, pl. 23^bis. [58]Trans. Zool. Soc. London, vol. 8, 1872, p. 223. [59]Ostéographie des Cétacés, p. 615, pl. 23^_bis_. [60]Trans. New Zealand Inst., vol. 10, 1878, p. 339. [61]Trans. N. Z. Inst., vol. 10, 1878, p. 339. Hector remarks that in the skeleton studied by Flower there were twelve caudals with facets for chevrons, but I do not find it so stated in the original account. [62]Proc. Acad. Nat. Sci. Phila., Dec. 1869, pp. 191, 192. INDEX. A Academy of Natural Sciences of Philadelphia, 76 Agassiz, L., 3 description of _Mesoplodon bidens_ by, 4 Alaska, _Ziphius_ from, 1 Allen, Dr. G. M., 3 American Museum of Natural History, 2, 3 _ampullatus_ (_Balæna_), 76 (_Hyperoödon_), 76 _arnuxii_ (_Berardius_), 68 B _bairdii_ (_Berardius_), 60 _Balæna ampullatus_, 76 _rostrata_, 76 _Berardius_, 60, 77 from California, 1 from Pribilof Islands, 1 specimens of, in National Museum, 1 _Berardius arnuxii_, chevron bones of, 74 coloration of, 66 distribution of, 77 external dimensions of, 67 size of, 66 skeleton, dimensions of, 75 skull, dimensions of, 68 teeth, dimensions of, 70 vertebræ of, 73, 74 vertebral formula of, 72 _Berardius bairdii_, 2, 60 chevron bones of, 74 coloration of, 66 description of a young, from Bering Id., 64 distribution of, 77 earbones of, 69, 83 external dimensions of, 64, 67 from Bering Island, 1, 60 from Centerville Beach, Cal., history of, 2, 63 from St. George Island, Alaska, 2 external dimensions of specimens, 62 history of, 61, 62 from Trinidad, Cal., 2 humerus of, 74 original description of, 65 scapula of, 74 size of, 66 skeleton of, 72 skeleton, dimensions of, 75 skull of, 68 skull, dimensions of, 68 sternum of, 74 teeth of, 70 teeth, description of, 70 teeth, dimensions of, 70 ulna of, 74 vertebral formula of, 72 _Berardius vegæ_, 60 Bering Island, _Mesoplodon stejnegeri_ from, 24 Ziphiidæ from, 1 _bidens_ (_Mesoplodon_), 4, 76 (_Physeter_), 4 Boston Society of Natural History, 3