The Diplodocus 5 



strata a few very primitive mammals. In the Ceno 

 zoic rocks occur plants, fishes, reptiles, birds, and mam- 

 mals, gradually becoming, as we approach the top of 

 the series, more like the creatures which to-day exist 

 upon the globe. Finally on top of the Tertiary we 

 find the soil and gravel in which man of to-day plays 

 his part. 



The reptiles, which most concern us in this narrative, 

 reached their highest development in Mesozoic times 

 in point of numbers and variety of species. The Meso- 

 zoic age has been called 'the age of reptiles," as the 

 Cenozoic has been called 'the age of mammals." 

 But many of the reptiles of the Mesozoic were not like 

 the reptiles of to-day. There were great groups of 

 them which have become totally extinct, leaving no 

 survivors at the present time. Among these were the 

 dinosaurs. Towards the close of the Mesozoic age 

 they attained their greatest development, and then in 

 early Cenozoic times gradually died out. There were 

 probably hundreds, even thousands, of different kinds 

 of dinosaurs, which at one time lived upon the globe. 

 We know that some of these were quite small; others 

 were the hugest animals which have walked on four 

 feet upon the surface of the globe. It was the discovery 

 of fragments of some of these larger reptiles which led 

 Sir Richard Owen, the great English naturalist, to 

 coin a name for them, compounded of two Greek 

 words, oeivoq (deinos), meaning 'terrible," and aaupos 

 (saurus), meaning 'lizard." Dinosaurs are reptiles, 

 which lived in the Mesozoic and at the beginning of the 

 Cenozoic ages, millions of years ago. As I have inti- 

 mated, not all of them were "terrible." Some of them 

 were quite small. And these smaller reptiles are only 

 called dinosaurs, because they belong to the same natural 



