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Bashford Dean Memorial Volume 

 DEVELOPMENT OF THE TEETH 



Among Dean's drawings of Heterodontus japonicus are four figures, which were 

 found mounted in serial order, illustrating the development of the teeth. These are 

 reproduced as my Text'figures 66 to 69. There are no records concerning the original 

 drawings, neither accompanying the drawings nor in Dean's notebooks. 





Text-figure 67- Text-figure 68 



Interior of the mouth and pharynx of a young (probably recently hatched) Japanese Bullhead Shark, 



Heterodontus japonicus. 

 Text-figure 67. Roof of the oro-pharyngeal cavity, revealing the teeth of the upper jaw, the breathing 



valve, and the pharyngeal denticles. 



Text-figure 68. Floor of the oro-pharyngeal cavity, showing the teeth of the lower jaw, also both oral 



and pharyngeal denticles. 

 After drawings left by Bashford Dean. 



The earliest stage, represented by Text-figure 66, represents the roof of the mouth 

 cavity viewed from below. This drawing was made from the 78-mm. embryo, in Dean's 

 collection, described and figured (Figure 38, plate III) in the present article. The lower 

 jaw of this embryo has been cut away in order to expose the roof of the mouth. I have 

 compared this dissection with Dean's drawing (Text-figure 66) and can state that the 

 drawing corresponds, in every detail, with the structures revealed by the dissection. 

 Teeth are not yet visible; but the arch-like dental ridge (formed by the lower surface of 



