DESCRIPTION OF THE PLATES. 



11 



of the base ; b, parallel vertical medullary- 

 canals ; c, calcigerous tubes radiating 

 therefrom. 



PLATE 27. 



Transverse section of portions of two con- 

 tiguous teeth, showing a, their uniting 

 suture ; b, area of medullary canal ; 



c, dentinal tubes radiating therefrom, 

 (with an enlarged outline at the side) ; 



d, intermediate osseous or cemental tissue 

 binding together the denticles which form 

 the compound tooth. Original. 



PLATE 28. 



Fig 1 . — The dental plate of the upper 

 and lower jaw of the Southern Chi- 

 meera, (Callorhynchus australis). Fig. 2, 

 Side view of the same. Fig. 3. Vertical 

 longitudinal section of the same. Ori- 

 ginal. Fig. 4. Outer side of small an- 

 terior and large posterior or lateral dental 

 plates of the upper jaw of the Chimcera 

 monstrosa. Fig. 5. Inner side of the 

 same. Fig. 6. Outer side of the single 

 dental plate of the lower jaw of the same. 

 Fig. 7. Inner side of the same. Fig. 8. 

 Horizontal section of the same. Agassiz. 

 Fig. 9. Part of the lower jaw of a Shark 

 (Galeus) pierced by the barbed caudal 

 spine b, of a Sting- ray (Trygon,) show- 

 ing the effect of the wound of the dental 

 matrix, in the teeth which have advanced 

 in their revolving course over the jaw. 

 a, one of these teeth erect in the row 

 which is in use. Andre.* 



PLATE 29. 



Fig. 1. — A section of the dental plate 

 of a Chimeera across the medullary ca- 

 nals, magnified 50 diameters by re- 

 flected light. Fig. 2. A section a little 

 obliquely to the course of the medullary 

 canals. Original. 



* Philosophical Transactions, 1678. 



PLATE 30. 



Fig. 1. — A portion of a fossil jaw of a 

 Lepidotus Mantellii. Fig. 2. Molars and 

 alveoli of the prehensile intermaxillary 

 teeth of Placodus Andriani. Fig. 3. 

 Detached prehensile intermaxillary tooth 

 of ditto. Fig. 4. Side view of dentary 

 piece of the lower jaw of ditto. Agassiz. 



PLATE 31. 



Part of vertical longitudinal section of a 

 tooth of the Lepidotus Mantellii, magni- 

 fied 300 linear diameters. Original. 



PLATE 32. 



Vertical section of a tooth of a Sphcero- 

 dus magnified 50 linear diameters. Ori- 

 ginal. 



PLATE 33. 



Fig. 1 . — Grinding surface of a tooth of the 

 Sphcerodus gigas. Fig. 2. Vertical sec- 

 tion of the same. Fig. 3. A portion of 

 the section in PI. 32, magnified 500 

 linear diameters. Original. 



PLATE 34. 



Fig. 1. — Part of fossil vomer with teeth 

 of Pycnodus rugulosus. Fig. 2. Vome- 

 rine teeth of Pycnodus Bucklandi. Fig. 3. 

 Side view of fragment of a vomer of 

 Pycnodus dydimus. Fig. 4. Side view of 

 lower jaw and teeth of Gyrodus jurassicus . 

 Fig. 5. Upper view of the same. Fig. 

 6. Side of single tooth of Gyrodus rugu- 

 losus. Fig. 7. Grinding surface of ditto. 

 Fig. 8. Basal surface of ditto. Agassiz. 



PLATE 35. 



Fig. 1. — Portion of jaw of a recent Sau- 

 roid (Lepidosteus osseus), showing the 

 large conical laniariform teeth, and the 



