American natural historyPart I, Mastology (Volume 3) . dvance of the head, by a sort of beak, smallerthan the rest of the head. They are destitute ofccecum. Vol. III.—H CHAPTER VII. Section I.—Size of the head bearing the ordinaryproportion to that of the body. Genus?—Dolphin; Delphinus; L. GENERIC CHARACTERS. The form of the head is very various; there isbut one, semilunar, external orifice to the nostrils,which is situated upon the crown of the head; thetrunk of the body is elongated; the tail fin is large,bifurcated and horizontal. Dental System. The teeth of the pisciverous cetaB ^scarcely
American natural historyPart I, Mastology (Volume 3) . dvance of the head, by a sort of beak, smallerthan the rest of the head. They are destitute ofccecum. Vol. III.—H CHAPTER VII. Section I.—Size of the head bearing the ordinaryproportion to that of the body. Genus?—Dolphin; Delphinus; L. GENERIC CHARACTERS. The form of the head is very various; there isbut one, semilunar, external orifice to the nostrils,which is situated upon the crown of the head; thetrunk of the body is elongated; the tail fin is large,bifurcated and horizontal. Dental System. The teeth of the pisciverous cetaB ^scarcely differfrom each other, except in number, all appearingto have the same form. They are conical andslightly hooked; only the larger species have largerteeth than the smaller, and when their series arenumerous, the anterior and posterior are smallerthan those in the middle. None of them have thealveolar processes divided, nor multiplex roots; thedental capsule remains for a long time free at thebase; but these teeth are not always growing, as the. THE TRUE DOLPHIN. 59 capsule is eventually obliterated. Then anotherevent occurs; ossification of the jaws takes placewithin the aveoles, and as the teeth are not opposedto each other, and no force retains them in theirplaces, they are soon thrust out and disappear. Thisexplains the very variable number of teeth we findin dolphins of the same species, and still more soin those of different species. Thus, not having ob-served between the teeth of dolphins any essentialdifference of form, and their differences of numbernot being determinate, we have nothing but the formof their heads from which to establish the genericdifferences. Species I.—The true Dolphin.* Delphinus Delphis; L. Le Dauphin: Bonnaterre ; Cetol. 20, pi. x, fig. VuJgaire : Desm. Mammal, sp. 758, p. 514. [Called Grampus, Porpess, Herringhog, Dolphin.~] Hitherto the subjects of our study have beeninhabitants of grassy plains, or shady forests ; themargins
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