UPPER, OR FLINTY CHALK. 225 



but no where more abundantly than in the chalk of the South Downs, 

 in the immediate vicinity of Lewes. 



The specimens are generally imperfect and distorted, and afford but 

 slight indications of the form of the original; but few examples having 

 been found, in which the number and situation of the fins, and other 

 parts essential to the determination of the genus, or species, are distinctly 

 exhibited. Yet, in many instances, their general characters are suf- 

 ficiently defined, to prove their entire want of correspondence with any 

 known existing species. 



The teeth and palates are remarkably beautiful, their original substance 

 being heightened by an impregnation with iron, and their natural polish 

 and sharpness remaining uninjured. The vertebrae and other bones are 

 of a reddish brown colour, and very friable. 



The fins and scales possess a glossy surface, are exceedingly brittle, 

 and both in colour, and in the mode of their preservation, perfectly re- 

 semble the ichthyolites of Monte Bolca. 



Of the cartilaginous fishes, the teeth of several species of Squalus or 

 shark, are most frequent; the vertebra are also occasionally met with, but 

 no decided examples of any other part of these animals have hitherto been 

 discovered. 



99. Vertebrae of an unknown species of Squalus. Tab. xxxiii. fig. 10. 



The specimen here represented exhibits two vertebrae, and the section 

 of a third, imbedded in chalk, and is part of a large mass containing 

 eleven others. The vertebree are concave both anteriorly, and posteriorly; 

 but no traces of the spinous, or transverse processes remain. They re- 

 semble those of the recent Squalus ?naximus; and correspond both in size, 

 form, and colour, with the fossil vertebrae, figured in the Oryctographie de 

 Bruxelles, PI. ii. B. G. and PI. iii. B. 



The latter are 38 in number, and articulated to each other, forming a 

 column more than five feet long; they are thus described by Blainville*: 

 " Dans le milieu de la pierre a chaux d'une carriere des environs de 



* Nouveau Did, d'Histoire Nat. Vol. xxviii. Art. Ichthyolites. 



G G 



