Fig. 3. Fig 4. 



teeth 3 and 4 in the scheme of fig. 2, at a stage of' development 

 somewhat vouiiger tlian was at inv disposal. The agreement is so 

 striking tliat only the more powerful development of the primitive 

 pulp-cells in fig. 4 proves thai it is not a teeth-band with dental 



a. 



CO. 





■■^^3. 



rrv 



^>^ 



;^.- 





/^. 







sm 





I d. 







It >>'f vy " 





i' '* 



M 



J f 





Fig. 5. 

 Proceedings Royal Acad. Amsterdam. Vol. XVIII. 



47 



