Asferospoudyli, 



89 



Notidanns are known from the Lithographic 8toue of Bavaria 

 and the Upper Ci-etaceous of Mount Lebanon, bnt there are 

 none in the Collection. Numerous teeth are shown from 

 Jurassic, Cretaceoas, and Tertiary Formations, and it is note- 

 worthy that the largest and most complex teeth ai'e those of the 

 latest deposits (Fig. 119). The Cestraciontida? are also primi- 



FiG. 119. — Tt'C'iii 01 ^otidarMS (jigM, Sism.; Keil Crag, Suffolk. 



tive and represented only at the present day by the Port Jackson 

 Shark {Gestracion, Fig. 109, p. 82). Their extinct representa- 

 tives are extremely numerous. As in (Jestraciou (Fig. 120), the 

 majority of the teeth are always adapted for crushing, thoucrh 



Table- oase, 

 No. 27. 



Fig. 120.— Jaw of Port Jackson Shark, Costracion PhUippi (recent). 



some in front are prehensile and many are cuspidate. Their 

 variation in different parts of the mouth is thus so great, that 

 it IS often almost impossible to name detached fossil teeth. As 

 m Cestrasioii, also, each of the two dorsal fins is invariably pro- 



