374 



HISTORICAL GEOLOGY. 



teeth could hardly have been less than sixty to seventy 

 feet long. 



Reptiles. The reign of reptiles is past. The Reptilian 



dynasty is overthrown. 

 This class no longer oc- 

 cupies a prominent place 

 in history. In geological 

 history the ruling class 

 is always the fittest to 

 rule, which can not al- 

 ways be said of the 

 reigning families in hu- 

 man history. 



The great char- 

 acteristic reptiles 

 of the Mesozoic 

 are all extinct. 

 Among great rep- 

 tiles, the crocodili- 

 ans alone remain. 

 The reptiles of 

 the Tertiary are 



FIG. 338. Tertiary fishes Sharks : Carcharodon J 



megalodon, x . (After Gibbes.) 01 the Same am- 



ilies as now exist, 



viz., crocodiles, turtles, snakes, lizards, frogs, toads, and 

 salamanders. Snakes seem a low type, and yet were intro- 

 duced only in the Tertiary. But they are not low in the 

 sense of undeveloped. They have developed backward 

 they are an example of a degraded type. The tailless am- 

 phibians (frogs and toads) are undoubtedly the highest 

 among amphibians ; for they pass through the tailed stage 

 (tadpole) in embryonic life. These tailless amphibians 

 were introduced first in the Tertiary. The biggest known 

 t-urtle (Colossochelys) was found in the Miocene of India. 

 Its shell was twelve feet long, eight feet wide, and seven 

 feet high. 



