364 



Plate XXXI. 



Tankoliasaurus oioeni, Hector. 



A, B. Portion of liead and lower jaw. (No. lie, one-fourth natural size.) 



A, upper surfacfe of cranium ; A', side view of tlie same ; B, fragment of the lower 

 jaw, seen from above, and restored to its proper position relative to the cranial frag- 

 ment ; B', lower jaw seen from the right side. These bones are much broken, and the 

 drawing of the lower jaw is to some extent a restoration. 



C. Paddle bones. (No. 11&, one-fourth natural size. ) 



A vein of calcspar, which is shown in the drawing, passes through the ulna and 

 across the articulations with the humerus above and the carpal below. In the slab the 

 radius has been displaced from its proper position, but has been restored in the drawing, 

 and fits exactly with the other bones into its position. On the same slab, but not 

 connected with paddle bones, are fragments of ribs and of a smooth, radially-striated 

 pelvic (?) bone, not represented on the plate. 



Description of Plates XXIV.— XXVI. 



Plate XXIV. — A (a). Inner parapet of dentary bone of Leiodoii. {b). Outer parapet 

 of dentary bone. (c). Floor of dentary bone. {d). Cementing alveolus, (e). Dental 

 fossa. (/). 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 (h) might 

 be considered the enamel, if really any such distinct layer exists in the teeth' of the 

 Leiodon. 



Gr [a, b, c). Tooth of Mauisaurus ? 



H (a, h). 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, (h). Outer 

 parapet of dentary bone. (c). Coronoid bone. [d). Descending process of dental. 

 (cZ'). Angular bone. (e). Opercular bone. (/). Imier parapet of dentary bone. (j/). 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 (TaniivJiasaurus). The 

 lines XY should be vertical. 



