DESCRIPTION OF THE PLATES. 



19 



losaurus Bucklandi : a, successional teeth 

 b, outer alveolar wall ; c, transverse par- 

 titions. Fig. 9. Edge- view of a tooth, 

 with portion of jaw, of the Megalosaurus. 

 Fig. 10. Side view of the same tooth, 

 with dotted outline of pulp-cavity. Fig. 

 11. Transverse section of ditto. Buckland. 



PLATE 70. M. 



Fig. 1. — Nat. size, of Fig. 2, part of a 

 transverse section of the tooth of the 

 Megalosaurus, magnified 250 diameters. 

 Fig. 3. A peripheral portion of the 

 same, magnified 500 linear diameters : 



a, dentine ; b, boundary cells between 

 the dentine and c, the enamel. Original. 



PLATE 71. 



Outline of a transverse section of the tooth 

 of the Iguanudon, and a magnified view 

 of the moiety including the pulp cavity a ; 



b, the vaso-dentine ; c, stratum of minute 

 cellules. The opposite part of the section 

 is composed of hard un vascular dentine. 

 Original. 



PLATE 72. 



Fig. 1. — A portion of jaw, with two teeth, 

 of the Leiodon anceps: a, crown; a\ 

 anchylosed base ; b, fractured base of 

 crown. I 1 Transverse section of crown. 

 Fig. 2. Fractured anchylosed base of the 

 same. Fig. 3. Crown of the tooth of 

 the Polyptychodon continuus. Fig. 4. Front 

 and back views of the crown of a tooth 

 of the Polyptychodon interruptus. 4" Out- 

 line of transverse section of same tooth. 

 Fig. 5. Outline of transverse section of 

 the tooth of the Pliosaurvs. Original. 



PLATE 73. 



Fig. 1 . — A tooth of Ichthyosaurus inter- 

 medins. Fig. 2. A tooth of Ichth. lon- 

 chiodon. with a transverse section of 



the grooved base below. Fig. 3. A tooth 

 of Ichth. platyodon, viewed edge-wise with 

 an outline of the transverse section of the 

 crown. Fig. A. A tooth of Icht h. communis, 

 with an outline of the transverse section of 

 the crown. Fig. 5. A tooth of Ichth. tenui- 

 rostris. Fig. 6. A tooth of the Ichth. platyo- 

 don, showing the cavity a, produced by the 

 pressure of a new tooth. Fig. 7. A sec- 

 tion through the tooth and lower jaw of 

 the Ichth. communis, showing the young 

 tooth, c, which has penetrated into the 

 cavity formed by progressive absorption 

 in the fang or base of the old tooth, a, 

 remnant of the pulp-cavity ; b, consoli- 

 dated base ; d, is a section of the dental 

 canal. Fig. 8. Section of a tooth of the 

 Ichth. communis showing a, remains of 

 the pulp -cavity in the crown, filled by 

 spar; b, ossified base. Fig. 9. Portion 

 of alveolar groove with indications of 

 septa. Fig. 10. Tooth of the Plesio- 

 saurus macrocephalus. Original. 



PLATE 73 A. 



Fig. 1. — Longitudinal section of the crown 

 of the tooth of the Ichthyosaurus inter- 

 medins, magnified 250 linear diameters. 

 Fig. 2. A peripheral portion of the same 

 section, magnified 400 linear diameters : 

 a, dentine ; b. enamel, nat. size. Original. 



PLATE 74. 



Fig. 1 . — Longitudinal section of the apex of 

 the crown of the tooth of the Plesio- 

 saurus Havjkinsii, magnified 250 linear 

 diameters. Fig. 2. A peripheral portion 

 of the same section, magnified 700 linear 

 diameters. Original. 



PLATE 75. 



Fig. 1. — A tooth of the Crocodilus bipor- 

 catus, with the size and form of the 

 b 2 



