DEVELUPMENT OF TEETH IN HATTEKIA PUNCTATA. 183 



becoming detached from the bone by absorption at its base 

 internally, and also that there is a further absorption of bone 

 at some depth, a developing tooth {t. s. 2) being found at 

 this point. Serial sections through the left premaxilla 

 confirm all these observations, and show that in all essential 

 respects the second successional tooth resembles the first 

 (fig. 18, t. s. 1) in its relations to the neighbouring parts. 

 Comparison of figs. 20, 21, and 22, will make clear the order of 

 tooth change in the premaxilla up to the stage of my largest 

 young specimen. 



The number of maxillary teeth on each side, visible with- 

 out dissection, was thirteen, regularly alternating in size 

 throughout, although the three anterior differed somewhat in 

 size from the following teeth. Microscopic examination 

 shows that the first tooth is one which has only recently been 

 formed (fig. 23, t. s. 1). Its pulp cavity is wide, its enamel 

 is almost undamaged, it is not j^et fused with the bone, and it 

 has evidently just grown up from the area (indicated in the 

 figure by lighter shading), where bone absorption had been 

 proceeding. There is no doubt as to the successional cha- 

 racter of this tooth, although I have not found its early 

 stages in any of my specimens. I am unable to say whether 

 it replaces two or only one of the preceding teeth. 



The palatine teeth arc six in number on each side, some 

 being large and others small, but they show a less definite 

 alternation than do the marginal teeth. 



In the lower jaw we find on each side three anterior teeth, 

 the outer being a little larger than the other two. Posterior 

 to these are thirteen teeth alternating in size, but all of them 

 small, and further back still are three or four larger teeth 

 of uniform size. Here, then, we see that whereas in the 

 maxilla all the teeth belong to the alternating series, in the 

 mandible there is already a commencement of a posterior 

 uniform series. In this specimen I found no indication of 

 replacing teeth in the lower jaw. 



In the middle line of the roof of the mouth, about opposite 

 the ninth maxillary tooth, and just anterior to the line joining 



