FISH-LIZARDS. 79 



the period of the 



Oolites and Chalk, 



till they finally died 



out, so far as we are 



aware, with the close 



of the Chalk period. 



The Fish - Lizards 



are, therefore, char- 



acteristic of the 



Secondary period, so 



that when we pick m y jm ^ 



up one of the joints j 



of their backbones 



(of which more 



anon), we know that Hv!&<9 ^SlS 



it must have come 



from some part of 



that great system, 



even though we find 



it embedded in the 



gravels lying above 



the Tertiary system. 



One other impor- 11^H "( 



tant point remains 



to be mentioned in 



connection with the 



beds in which the 



remains of these 



Fish-Lizards occur ; 



and this is, that they 



