EXTINCT REPTILES 



sidered as one double order. Extinct repre- 

 sentatives of all these orders are found right 

 away down through the Mesozoic strata to the 

 Trias (see table of strata, p. 60). But there is 

 nothing very astonishing about them excepting 

 the large size of some of the extinct tortoises 

 and snakes, and the fact that the older extinct 

 crocodiles had the opening of the nose-passages 

 into the mouth-openings, which we and all air- 

 breathing vertebrates also possess, placed far 

 forward as they are in the more primitive air- 

 breathers, whereas Hving crocodiles have them 

 pushed ever so far back to the very furthest 

 recess of the long ferocious mouth, from which 

 arrangement it results that the modern crocodile 

 can have its mouth full holding the body of a 

 victim under water whilst the air passes from the 

 tip of its nose through the long nasal passage 

 to the very back of its mouth and so to its 

 lungs. This convenience was not enjoyed by 

 primitive crocodiles. 



The great interest in regard to extinct reptiles 

 centres in those which were so entirely different 

 from the reptiles of to-day that naturalists have 

 to make separate orders for them. Many of 

 them were of huge size. They flourished in the 



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