A HISTORY OF SURREY 



its many-ridged teeth being uniformly conical instead of more or less 

 distinctly trihedral. 



The second reptile is a huge marine turtle allied to the existing 

 leathery turtle (Dermatocbelys) ; it was named by the present writer 1 

 Protostega anglica on the evidence of two imperfect specimens of the 

 upper arm-bone (humerus) in the British Museum, one of which was 

 obtained from the chalk of Lewes and the other from that of Dorking. 



In several geological works it is stated that remains of another 

 reptile, Mosasaurus graci/ts, have been met with in the chalk of the 

 county. These, however, are now known to belong to fishes of the 

 genus Pacbyrhizodus, whose teeth are of unusual size and strength. 



Some of the most common fish-remains that occur in the Surrey 

 chalk are the well-known crushing palatal teeth of rays of the genus 

 Ptychodus, of which several species are represented in the county. Of 

 Ptychodus mammillaris the British Museum possesses twenty associated 

 teeth in a block of chalk from Guildford, and likewise an associated set of 

 twenty-three teeth obtained from the same locality in 1851 ; in addition 

 to these there are also teeth from the chalk of Dorking. In the same 

 collection there are likewise teeth of Pt. rugosus from Guildford, of Pt. 

 decurrens from Dorking, as well as of Pt. polygyrus from a chalk-pit on 

 St. Catherine's Hill near Guildford, while, there is a single large tooth of 

 Pt. latissimus from Croydon and a smaller one referable to the same species 

 from Guildford. A Cretaceous ray belonging to the genus Squatina is 

 represented in the national collection by several vertebra? from the chalk 

 of Dorking. 



Among sharks, a tooth from the chalk of Guildford in the British 

 Museum is referable to Notidanus microdon, one of the comb-toothed 

 representatives of the group. In the same collection are an associated 

 set of eleven vertebrae and a fin-spine from Guildford, as well as a tooth 

 from Warlingham near Croydon, referable to Cestracion rugosus, a com- 

 paratively rare species of pavement-toothed shark, nearly related to 

 the living Australian representative of the genus. Another type 

 of pavement-toothed shark is represented by Synecbodus illingivortbi 

 (formerly known as Acrodus] of which the British Museum possesses 

 teeth from the chalk of Guildford and Dorking. Among other sharks 

 Scapanorhynchus rhaphiodon is represented in the national collection by 

 teeth from the upper chalk of Shalford near Guildford, and Purley near 

 Croydon, as well as by others from the lower chalk of Guildford. 

 Scapanorhynchus was long regarded as an extinct type, but it appears 

 closely allied to, if not identical with, a living Japanese form described 

 as Mitsikurina. Of porbeagle sharks (Lamna) the British Museum con- 

 tains teeth from Surrey belonging to two species, L. sulcata and L. appendi- 

 culata, the latter being frequently referred to as Otodus appendiculatus. 

 Two teeth from the lower chalk of Guildford in the same collection are 

 assigned to the nearly related Oxyrbina angustidens, while the remains of 



1 Catalo&te Fossil Reptilia British Museum, pt. iii. p. 229 (1889). 



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