DESCRIPTION OF THE PLATES. 



PLATE 9. 



Longitudinal section of a rostral tooth 

 under a low power, showing the course 

 and anastomoses of the vascular canals. 

 Fig. 2. A transverse section of the tooth, 

 magnified 350 linear times, shewing the 

 reticular dentinal tubes continued from 

 the vascular canals, and the clear inter- 

 spaces which define each system of canals. 

 Original, 



PLATE 10. 



Fig. 1. — Side view of the skull and teeth 

 of the Cestracion Philippii. Fig. 2. 

 Oblique view of the skull of the Monk- 

 fish (Squatina angelus) : a, antero-supe- 

 rior rostral cartilage (' intermaxillary' of 

 Cuvier) ; b, postero-superior rostral carti- 

 lage (' maxillary' of Cuvier) ; c, inferior 

 rostral cartilage (' premandibular' of Cu- 

 vier) ; d, confluent maxillary and palatal 

 bones ; e, confluent dentary and angular 

 pieces of the lower jaw ; both figures 

 \ nat. size. Original. 



PLATE 11. 



Fig. 1. — Portion of fossil jaw with verti- 

 cal rows of six teeth of the Hybodus 

 grossiconus. Fig. 2. Lower jaw and 

 teeth of the Cestracion Philippii. Fig. 3. 

 Detached grinding tooth, showing the 

 contracted base of attachment of Cestra- 

 cion. Fig. 4. The same with a section 

 removed from the crown, showing the 

 orifices of the vascular canals. Original. 



PLATE 12. 



A longitudinal section of a grinding tooth 

 of Cestracion Philippii, magnified 150 

 linear, showing the general course of 



the vascular canals and of the calcige- 

 rous or dentinal tubes which radiate 

 therefrom. Original. 



PLATE 13. 



A portion of the same section magnified 

 350 linear, showing the sub-parallel 

 tubes in the hard peripheral dentine, 

 and the reticulate disposition of the 

 tubes in the interspaces of the canals. 

 Original. 



PLATE 14. 



Five teeth in natural relative position of an 

 allied extinct cartilaginous fish (Acrodus 

 nobilis), nat. size ; and half of a vertical 

 section of one of the teeth, magnified 30 

 linear diameters. Original. 



PLATE 15. 



Portion of a vertical section of a tooth of 

 Acrodus nobilis, more highly magnified : 

 a, large vascular canals at the base of the 

 tooth ; b, smaller vascular canals in the 

 body of the tooth ; c, calcigerous or den- 

 tinal tubes radiating from the vascular 

 canals ; d, the sub-parallel tubes in the 

 outer layer of hard dentine ; e, modified 

 enamel. Original. 



PLATE 16. 



Fig. 1. — Section of a dried head of an 

 Eagle-ray (Aetobates Narinari). Fig. 2. 

 A section of the enamel and hard 

 dentine of the tooth of Acrodus nobilis, 

 magnified 400 linear times ; showing the 

 continuation of the fine terminal branches 

 of the dentinal tubes into the so-called 

 enamel. Fig. 3. One of the medullary 

 canals, with its radiating system of cal- 

 cigerous tubes, divided more or less 

 obliquely from the body of the tooth 



