TOOTH-GERMS IX A WALLABY. 933 



Opinion a tooth vestige (e). It lies close beneath the alveolar 

 margin (text-tig, 186). 



Then occurs a further interval through which the tooth-band 

 persists without giving rise to any further dental enlargements. 

 Three further teeth {h, i, and j) of premolariform pattern, follow 

 in the cheek region. Of these the middle one is considerably 

 the most extensive, the posterior one being quite small. To the 

 two anterior teeth there are indefinite indications of lingual 

 downgrovvths of the dental lamina. 



As in the upper jaw there are indications of eight teeth, five 

 antemolars and three maxillary teeth, 



A general impression of the number and relative positions of 

 the dental structures in both jaws may perhaps be best realised 

 by the following diagram, which has been drawn to scale in the 

 hoi'izontal direction. 



Text-fig. 187, 



^^Z" ^..i:::::^ 



\7 



Diagram showing number and relative positions of the tooth-germs in the jaws 

 of Stage I. Calcified germs more heavil}' outlined. 



Stage II. 



The difference in size between this embryo and that of Stage I 

 is very considerable, and as a consequence a number of additional 

 teeth have appeared in both jaws and those which were present 

 in the earlier stage have developed very materially. It is un- 

 fortunate that \ve have not had at our disposal an embryo of 



Proc. ZooL, Soc— 1911,No. LXIY, 64 



