106 LIFE ON THE EARTH. 



II. Chelonida (Turtles), in. Ophidia (Snakes), iv. La- 

 certilia (Lizards), and v. Crocodilia (Crocodiles), are 

 both recent and fossil ; and eight, viz. vi. Deinosauria, 

 vir. Thecodontia, vm. Pterosauria, ix. Anomodontia, 

 x. Sauropterygia, xi. Ichthyopterygia, xn. Labyrinth- 

 odontia, xm. Ganocephala are only found in a fossil 

 state. Among the marine tribes are some of the 

 Chelonida, all the fossil Ichthyopterygia, Sauropte- 

 rygia, some of the Crocodilia and Lacertilia, possi- 

 bly the Thecodontia 1 , omitting the Chelonida. They 

 stand in the following order of time : 



Mososaurus Chalk. 



Leiodon Chalk. 



Pleiosaurus Kimmeridge Clay. 



Cetiosaurus Great Oolite and upwards to Wealden. 



Teleosaurus Lias and upwards to Chalk. 



Ichthyosaurus Lias and upwards to Chalk. 



Plesiosaurus Bone Bed, Aust, and upwards to Chalk. 



Stagonolepis 2 Triassic Sandstone of Elgin. 



Thecodontosaurus. Conglomerate, Bristol. 



It will be seen hereafter that Terrestrial and 

 Freshwater Reptilia appear to be of higher antiquity 

 than the marine tribes yet discovered. Remains of 

 Chelonida appear to be about of the same antiquity 

 as the marine Saurians; they occur in the Red 



1 The fossil Crocodilia may perhaps have visited rivers and 

 the land ; their legs might allow of this, and their feet are not 

 unsuitable. 



2 Huxley, Geol Soc. Journal, 1859. 



