DEVELOPMENT OF TEETH JN HATTERIA PUNCTATA. 213 



successional teeth on its lingual side at a later stage (see also fig. 18). 

 (Stage T. X 60.) 



Figs. 20, 21, 22.— Three stages in the developineut and succession of teeth 

 in the premaxilla (riglit) of specimens 17 cm., 17'8 cm., and 21*2 cm. in 

 length. 1, 2, 3 are the teeth of the newly-hatched animal ; t. s. 1, 2, and 3, 

 are the successional teeth in the order of their formation. (L s. 1 in fig. 20 

 was missing in the preparation figured, but was inserted from sections). 

 X 10. 



Pig. 23. — Inner view of the anterior maxillary teeth of left side, from a 

 specimen 17"8 cm. in length, t. s. 1 is the first successional tooth of the 

 maxilla, which has cut the gum but is not yet fused with the bone. X 14. 



Fig. 24. — Transverse section across the vomers (vo.), cutting the two 

 vomerine teeth (/. v. I., r. v. t.) more or less longitudinally. The left tooth 

 had a considerable backward curve, which partly accounts for its division into 

 a free and an attached portion. From the same specimen as tiie last figure. 

 X 50. 



Fig. 25. — Inner view of anterior maxillary teeth of left side, from speci- 

 men 21*2 cm. in length. t. s. 1, 2, and 3 are the successional teeth, the 

 last being still deeply seated, x 14. 



Fig. 26. — Inner view of anterior mandibular teeth of left side, showing 

 two successional teeth, t. s. 1 no doubt replaced two of the earlier set (from 

 same specimen as last figure). X 14. 



Fig. 27. — Outline of marginal teeth of 21*2 cm. specimen. The uniform 

 series in the lower jaw already occupies considerable space, whereas all the 

 maxillary teeth are of the alternating series or their vertical successors (tiie 

 same may be said of the palatines at this stage). X 5. 



Fig, 28. — Portion of ground longitudinal section through the base of a 

 young tooth, to show tlie branching dentinal tubules {d. t.) with their pro- 

 longations into the enamel {d. I'.). X 300. 



Fig. 29. — Portion of a ground section through the specialised outer layei 

 of bone, on the lingual side of the adult lower jaw, to show tiie close 

 resemblance to enamel, b. c. Bone-corpuscles. X 300. 



