ROOM V. 



FISHES OF THE PLACOID ORDER. 



449 



spines ; the ichthyodorulites of this family are abundant in the Wealden, 

 Oolite, &c. 



Lies. 96. FOSSIL TEETH OF FISHES ; CHIEFLY OF THE SHARK FAMILY. 

 2. Carcharias. 3. Corax. 



1. Otodus. 

 5. Notidanus. 



6. Lamna. 



4. Oxyrhina. 

 7. Acrodus. 



8. Pycnodon tooth of a ganoid fish ; upper surface. 



9. Lateral view. 10. Ptychodus. 



CESTRACIONS. Of this family a few teeth have been found in the 

 Kentish Chalk, that belong to fishes of the existing genus Cestracion, 

 or Port Jackson Shark. A genus of this family, named Ptychodus 

 (rugous-tooth,) must have swarmed in the cretaceous ocean, for its large, 

 quadrate, channelled molars, are found in every quarry of the White- 



LIGN. 97. TEETH OF HYBODCS. 



Chalk (Lign. 96, 10) ; there are groups of from ten to fifty on blocks 

 of chalk in the Table-cases, 



Of the PRISTIDES, or Saw-fishes, there are a few teeth, and portions of 

 the beak, of two species, from the Eocene of Bracklesham. 



FOSSIL EATS. Instead of pointed teeth, the masticatory organs of the 

 fishes of this family are wide, flat, dental plates, composed of distinct 



GG 



