GENERAL CHARACTERS 7 



the lower jaw was close on six feet and that of the thigh-bone, 

 or femur, fully a yard, from which some estimate may be formed 

 as to the total dimensions of these monsters. As the plesio- 

 saurs and ichthyosaurs began to wane, their place was filled by the 

 sea-serpents, or Pythonomorpha, of the Upper Cretaceous, the 

 length of some of which is estimated at not less than forty feet. 

 Neither were these huge bodily dimensions by any means con- 

 fined to the extinct Mesozoic ordinal groups, for we find many 

 of the Lower Eocene, and even in some cases the later Tertiary, 

 representatives of modern groups far exceeding in point of size 

 their living relatives. The giant Eoclielone of the London Clay 

 had, for instance, a skull fully three times the size of that of 

 the modern leathery turtle, or kith {Dermochelys) which is itself 

 one of the largest of living reptiles ; while a snake {Gigaiitophis) 

 from the Lower Eocene of Egypt probably fell but little short of 

 fifty feet in length. Again, in the Lower Pliocene the gharial- 

 like Rhamphosuchus of India has been estimated to have reached 

 a length of between fifty and sixty feet ; while in the Pleistocene 

 the giant monitor ( Varanus prisats) of Queensland probably 

 grew to something like fifty feet. 



Finally, as the dinosaurs or giant land-reptiles, and the 

 earlier mammal-like theromorphs took the place during the 

 Mesozoic epoch now held by terrestrial mammals, while the 

 ichthyosaurs, plesiosaurs, and sea-serpents played the part of 

 the whales of our modern seas, so the flying pterodactyles ful- 

 filled the role of birds, which during the earlier part of that era 

 of the world's evolution were probably non-existent, while in the 

 later stages of the same they apparently occupied a subordinate 

 position and had not yet gained the dominion of the air. As 

 the crocodiles, tuateras, and tortoises and turtles of the Mesozoic 

 represented the reptiles of the present day, it is thus evident 

 that the reptilian class, at that distant epoch, occupied the 

 positions in nature now filled collectively by mammals, birds, 

 and reptiles, and that the title " age of reptiles " which has been 

 bestowed on the era in question is fully justified. 



" It is noteworthy," writes Dr. A. Smith Woodward, " that 

 nearly all reptiles with well-formed limbs — whether adapted for 

 habitual support of the body on land, for flight, or for con- 

 stant swimming — -flourished only before mammals and birds 

 became dominant ; the vast majority of the survivors during 



