64 Vertebrate Palaeontology of Cambridgeshire 



Passing on to the fishes of the Cambridge Greensand, it 

 may be noted that teeth of various sharks are among the most 

 common remains in this formation. The more simple types 

 of such teeth have been identified 1 with the species known as 

 Corax falcatus, Lamna appendiculata, Oxyrhina angustidens, 

 0. macrorkiza, and 0. mantelli, most of these ranging upwards 

 to the Chalk, although the fourth is restricted to the Gault 

 and Cambridge Greensand. Of another genus (Scapanorhyn- 

 chus) of the family Lamnidae there are three representatives 

 in the Cambridge Greensand, of which S. gigas is restricted 

 to that formation, while the other two, S. subulatus and 

 8. rhaphiodon, are typically from the Chalk. The genus was 

 long supposed to belong to an entirely extinct type, but is 

 now known to be closely allied to, if not identical with, 

 a shark from Japanese waters, named Mitsikurina. Fin- 

 spines described as Spinax major probably indicate sharks 

 of the genus Synechodus, which belongs to the family 

 Cestraciontidae, now represented by the Port Jackson shark. 

 Of the comb-toothed sharks (Notidanidae) the species Noti- 

 danus microdon, widely distributed in the Upper Cretaceous, 

 is met with in the formation under consideration. 



The solid tooth-like jaws, with their characteristic masti- 

 cating surfaces, or ' tritors,' of extinct generic types of fishes 

 allied to the living chimaera, or king-of-the-herrings, are far 

 from uncommon in the Cambridge Greensand. Thus the 

 genus Edaphodon is represented by the species E. laminosus, 

 E. crassus, E. reedi, and E. sedgwicki, of which the second 

 and third are confined to the present formation, while the 

 others have a wide range in the Upper Cretaceous, and 

 are not typically from Cambridgeshire. Of the allied genus 

 Ischyodus, the Cambridge Greensand likewise possesses four 

 specific representatives, of which /. latus and /. planus are 

 confined to that formation, while /. thurmanni and /. incisua 

 are typically from other horizons. 



Among the most beautiful of all vertebrate fossils from the 



1 See Smith Woodward, Proc. Geol. Assoc. xin. 196 (1893). 



