539 



Fig. 1. Section through the third upper Incisor of Dog 3 Weeks old; shewing a 

 Portion of the Deciduous and the Successional Tooth and Post-Permanent Downgrowth. 



present in Dasyums and possibly some other Marsupials ^). These 

 go-called pre -milk teeth are so regarded on account of their deve- 

 lopment on the labial side of the milk dentition. The next point to 

 determine is whether these latter are the true milk teeth, or whether 

 they may not belong to the permanent series. 



Leche(7) figures (fig. 129) in Myrmecobius a tooth in the incisor 

 region and a labial downgrowth, but no apparent trace of any other, 

 and calling the more fully developed one a milk tooth, the other, he 

 says, must be a pre-milk. Kükenthal (8), discovering strong swellings 

 of the dental lamina on the lingual side in Didelphys, had previously 

 attempted to show that the dentition of Marsupials was a persistent 

 milk one. 



Leche in support of this view calls attention to the fact that 

 Myrmecobius is a very primitive creature with mesozoic allies and 

 therefore likely to retain a primitive first dentition. Beyond this 

 I can find no definite reasons for regarding the teeth as Leche has 

 done. 



1) I gladly take this opportunity of expressing my indebtedness to 

 Mr. M. F. WooDWAKD who has kindly allowed me to examine his sections, 

 and to take photographs of those shown in fig. 3. 



35* 



