Description of Plates XXIV.—XXVI.
Plate XXIV.—A (a). Inner parapet of dentary bone of Leiodon. (b). Outer parapet of dentary bone. (c). Floor of dentary bone. (d). Cementing alveolus. (e). Dental fossa. (f). Primitive tooth. (g). Successional tooth.
A′ Side view of the same specimen.
B Transverse section of middle of crown of tooth.
C Base of tooth with surrounding alveolus, showing at (a) the encroachment of the successional tooth.
D Tooth from which the microscopic preparations were taken, showing the absorption of the alveolus at (a), where the successional tooth has forced its way out.
E Section of tooth showing the radiating calcygerous tubuli and the concentric contour lines.
F Section of tooth showing the calcygerous tubuli; the portion from (a) to (b) might be considered the enamel, if really any such distinct layer exists in the teeth of the Leiodon.
G (a, b, c). Tooth of Mauisaurus?
H (a, b). Tooth of Plesiosaurus traversii.
Plate XXV.—Section showing tooth, alveolus, and jaw-bone of Leiodon; the outline of the latter not very distinctly seen in the fossil. (a). Cementing alveolus. (b). Outer parapet of dentary bone. (c). Coronoid bone. (d). Descending process of dental. (d′). Angular bone. (e). Opercular bone. (f). Inner parapet of dentary bone. (g). Floor of dentary bone. (h). Pulp-cavity.
Plate XXVI.—A Section showing tooth of Leiodon, with channel communicating through the cement to the surface of the dentary bone.
B and C Sections of the jaw of an allied form to Leiodon (Taniwhasaurus). The lines XY should be vertical.