§33. FOSSIL TEETH OF SHARKS. 341 



beautifully displayed.* Scales and teeth are occasionally 

 found in flint ; sometimes adherent to the surface, and 

 in other instances imbedded in the stone. A fragment 

 of flint to which two minute scales are attached is figured 

 in Lign. 69, fig. 1 ; and the scales, highly magnified, are 

 represented in figs. 2 and 3. 



33. Teeth of sharks, &c. — Teeth of several genera of 

 fishes abound in the cretaceous deposits : and of these, by far 

 the greater number belong to the Sharks ; a family which 

 in the ancient, as well as in the modern seas, appears to 

 have been confined by no geographical limits. A group of 

 some of the usual forms is represented in Lign. 70. These 

 teeth possess a high polish, and are in an excellent state of 

 preservation ; they generally occur detached, owing to the 

 decomposition of the jaws, which from their cartilaginous 

 nature are but seldom preserved. A few specimens of the 

 fishes termed Hybodus.] have, however, been found with 

 several rows of teeth attached to the jaws. 



Large flat teeth, having a series of deep angular plaitings 

 on the crown, surrounded by a border of papillae {Lign. 70, 

 figs. 4, 5), are very abundant, and are commonly known as 

 " palates." They belong to a genus of the shark family called 

 Ptychodus (rugous teeth), allied to the Cestracion or Port 

 Jackson Shark. A group of teeth has lately been found in 

 the chalk by the Marquess of Northampton, which differ 

 but little from those of the recent living species. Dorsal 

 rays, or fin-bones, belonging to these fishes are occasion- 

 ally met with in the chalk ; the first known examples 

 were figured in my Fossils of the South Downs (Tab. 39). ± 



* For directions how to clear chalk fishes, see Medals of Creation, 

 vol. ii. p. 673. All my best specimens, most of which are figured in 

 the work of ML Agassiz, are now in the British Museum. 



f Medals of Creation, vol. ii. p. 609 ; Geology of the Isle of 

 Wight, p. 233. 



X Medals of Creation, vol. ii. p. 605. 



