DEVELOPMENT OF TEETH IN HATTEEIA PUNCTATA. 207 



recently cut the gum, whereas che inner is older and more 

 worn. The latter is no doubt the third successional, shown 

 still below the gum in my fig. 22, whilst the former is a 

 fourth successional, belonging, like the third, to the fifth 

 dentition. It is indeed the tooth represented as 

 hypothetical in my diagram c. The bone has not yet 

 grown down with the teeth to any extent. 



Of the three successional teeth of the maxilla, the 

 anterior is the least worn and the middle one the most. The 

 posterior is the third successional shown deeply seated in 

 fig. 25 [t. s. 3), the middle one is the second successional 

 {t. s. 2), whilst the anterior is a fourth successional (which I 

 have mentioned but not figured), and represents the fifth 

 dentition, having replaced the first successional (fourth den- 

 tition). Posterior to these three anterior teeth are from ten 

 to twelve of the alternating series, but there are as yet no 

 indications of the uniform series. The number of teeth in 

 the upper jaw belonging to the second and third dentitions is 

 slightly greater than I had supposed from my earlier speci- 

 mens. 



Taking the maximum of twelve as the number remaining 

 at this stage, and adding two for each of the successional 

 (maxillary and premaxillary), we arrive at twenty-two as the 

 number of alternating teeth represented on each side of the 

 upper jaw. This would give us eleven each of the second 

 and third dentitions, whereas the first has only nine in the 

 correspondiug region. The discrepancy does not, however, 

 constitute any serious objection to the view that the ances- 

 tors of Hatteria at one period possessed a dentition consist- 

 ing of a definite number of teeth, about ten (marginal) ' on 

 each side above and below, and that these were replaced 

 regularly by vertical successors, without increase in number. 

 As I have already said, the uniform series is almost certainly 

 a later acquisition. 



' The number of palatine teeth was probably 3 — 4 on each side, though 

 the evidence here is not so satisfactory as in the case of the marginal teeth. 

 The number of vomerine teeth at this period is quite uncertain. 



