DEVELOPMENT OP TEETH IN HATTEETA PUNCTATA. 195 



until the jaws have practically stopped growing. However, 

 most of the teeth of Hatteria retain their odontoblasts in an 

 active condition during the greater part of the life of the 

 animal, and it is possible that no further tooth change takes 

 place.i Burckhardt's opinion that the form of the 

 premaxillary teeth is due to concrescence is quite 

 erroneous, if by this term he means the fusion of dentine 

 with dentine before the tooth is fully formed; still more so 

 if he intends to imply the fusion of one enamel organ with 

 another to produce a compound tooth, as has been described 

 in the Chameleon. The anterior teeth of Hatteria at the last 

 stao-e I have investigated are successional teeth developed 

 quite independently of one another, and their fusion is pro- 

 duced by the formation of bone round their bases, which 

 even passes some little distance down their sides. The 

 premaxillary bones also grow down, so as to cause their 

 apical tooth-bearing edge to project considerably beyond the 



gum. . , „ 



In the maxillae of a full-grown specimen now before me 

 there are anteriorly on one side three, on the other four, well- 

 defined teeth. The insertion of these on the jaw is not at the 

 same level as that of the teeth posterior to them. The appear- 

 ance suggests that a small strip of the tooth-bearing edge has 

 been removed, and the teeth inserted along the exposed 

 surface This is in effect what has happened. As may be 

 seen from several of my figures, when a tooth is shed a large 

 absorption of bone takes place, and the new tooth is inserted 

 at a different level from the old one. The assumption that 

 each of these anterior teeth is a successional one seems quite 

 justifiable, in view of the fact that I have myself found 

 four successional teeth in various stages of development in 

 this region. Assuming, also, that each of these teeth has 

 replaced two others of the alternating series, the number of 

 teeth now left will agree approximately with the original 

 number (say sixteen) of the latter in the maxilla. Posterior 

 to these anterior teeth there is, as I have intimated, a distinct 

 > See Addendum. 



