THE EMPIRE OF THE GREAT REPTH.ES. 167 



Then .in the Jurassic and early Cretaceous the reptiles culmi- 

 nated, and presented features of magnitude and structural 

 complexity unrivalled in later times. At the same time the 

 Labyrinthodonts disappear, or are degraded into the humble 

 stations which the modern Batrachians now occupy. 



To understand the reptiles of this age, it will be necessary 

 to notice the subdivisions of their modern representatives. The 

 true reptiles now existing constitute the following orders : — 

 T, the Turtles and Tortoises (C/ie/om'a) ; 2, the Snakes (0/>/ii- 

 dia) ; 3, the Lizards {Lacertilia) ; 4, the Crocodiles and 

 Alligators {Crocodilia). All of these, except the snakes, are 

 well represented among Mesozoic fossils ; but we have in this 

 middle age of the earth's geological history to add to them 

 from five to seven orders now altogether extinct, and these not 



I'k;. 142.— Skeleton of hhthyosnurus. Li;is. ICngland. 



of low and inferior organisation, but including species far in 

 advance of any now existing both in elevation and magnitude, 

 and constituting the veritable aristocracy of the reptile race. 

 It will best serve our purpose here to consider chiefly these 

 perished orders and their history, and then to notice very 

 shortly those that now survive. 



The first of the extinct orders is that of the great Sea-lizards,^ 

 of which the now familiar Ichthyosaurus and Plesiosauriis ot 

 the English seas, to be seen in all museums and text-books, 

 are the types (Figs. 142, 1420; and i^2b). These were marine 

 animals of large size, but not fishes or amphibians. They were 

 true air-breathing reptiles, but with paddles for swimming 

 instead of feet, and some of them with long flattened tails 

 for steering and propulsion. They bore, in short, precisely 

 ^ Enalcosauria^ including Ichthyoptcry^ia and Saiiropterygia. 



