X. On the development of the teeth of fishes (Elasmobranchii and Teleostei)

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Abstract
The conformation of the jaws of the Elasmobranchii is such as to afford peculiar facilities for the study of the development of their teeth, and it has hence resulted that the older descriptions of the process approximate more closely to the truth than has been found to be the case in reptiles and mammals, and, I may now add, in osseous fish. The accounts given by Prof. Owen in his 'Odontography’ (p. 35) and 'Anatomy of Vertebrates’ (vol. i. p. 381) do not materially differ from one another; I will therefore make an extract from the latter work as embodying as concisely as possible the views of that anatomist, which are generally accepted as correct:— "It is interesting to observe in it (the class of Fishes) the process arrested at each of the well-marked stages through which the development of a mammalian tooth passes. In all fishes the first step is the simple production of a soft vascular papilla from the free surface of the buccal membrane; in sharks and rays these papillae do not proceed to sink into the substance of the gum, but are covered by caps of an opposite free fold of the buccal membrane; these caps do not contract any organic connexion with the papilliform matrix, but, as this is converted into dental tissue, the tooth is gradually withdrawn from the extraneous protecting-caps, to take its place and assume the erect position on the margin of the jaw.

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