DEVELOP.MKNT OF TEETH IN HATTEEIA PUNCTATA. 189 



ting teetli are subject to great modifications in later stages, 

 and this has no doubt affected their earlier development, so 

 that we may well consider them as originally siinilar to the 

 rest. At Stage R, then, No. 2 premaxillary, Nos. 2, 4, 6, 8, 

 10 maxillary (though here this is not quite constant as far as 

 the first five are concerned). No. 2 palatine, and Nos. 2, 4, 6, 

 8, 10 mandibular, belong to the earlier set of smaller teeth. 

 It is, I consider, a support to this view, that amongst the first 

 successional teeth to be developed are those formed liugually 

 to No. 2 premaxillary, and No. 2 mandibular, the first 

 palatine successional tooth being also lingual to the second 

 in order. In the maxilla the relations are not so clear, 

 though the third successional is lingual to one of the smaller 

 teeth, the first and second giving no indications of their exact 

 place of origin in any of my specimens. The second succes- 

 sional of the mandible lies at the base of two teeth, though 

 from its relations I believe it to have originated lingually to 

 the smaller one. I have already noted that these successional 

 teeth replace, undoubtedly in three cases, and very probably 

 in two others, two deciduous teeth of the alternating series. 

 Now according to my view, in the premaxilla3 of Hatteria the 

 following dentitions are represented : 



First, or embryonic — those shed during incubation. 



Second, — the smaller teeth ot" the alternating series (i.e. 

 the second in order). 



Third, — the larger teeth of the alternating series (i.e. 

 the first and third). 



Fourth, — the first and second successional. 



Fifth, — the third successional (which, as is required hy 

 my theory, evidently replaces onl}' one of the preceding 

 dentition). 



I have chosen the premaxillge for illustration, because they 

 retain their successional teeth in greater number than do the 

 other dentigerous bones, as far, at least, as my specimens 

 enable me to decide. 



I have endeavoured to correlate and account for the fore- 

 going anomalies of tooth succession by means of the following 



