452 The Outline of Science 



eating, the teeth of others point to a herbivorous habit. The 

 sharp incisors of some types may have been used to pierce the 

 shells of the eggs of waning Dinosaurs. According to some 

 authorities, many of the early mammals were arboreal, denizens, 

 perhaps, of estuarine and swampy forests. The advantage of 

 such a habitat or mode of life is suggested by the scant vegeta- 

 tion of the arid ground. 



Archaic Mammals 



During the geological Middle Ages (Mesozoic) the mam- 

 mals did not make much headway. Their opportunity was not 

 yet; it was still the Age of Reptiles. The mammals continued 

 a little folk, probably for the most arboreal, keeping out of the 

 way of the huge carnivorous dinosaurs, "stalking terrors such 

 as the world never saw before nor since." 



As a matter of fact, however, the giants disappeared, and 

 the pigmies had their innings. With the dawn of the Tertiary 

 time, the mammals began to possess the earth. Their giant 

 enemies had gone, and it is probable that the vegetative con- 

 ditions became more favourable. The grass began to spread like 

 a garment over the earth. 



I 



Modern Types of Mammals 



Progress was at first very gradual ; the early Tertiary mam- 

 mals were still pigmies and with very small brains ; but the point 

 is that they began to radiate out into old-fashioned marsupials, 

 carnivores, and hoofed mammals some of the last attaining ele- 

 phantine dimensions. 



As the primitive and archaic mammals disappeared, there 

 rose up in their stead the mammals of the modern type with 

 better brains and more plastic feet and teeth. We refer to such 

 families as Cats, Horses, Elephants, and Monkeys. The 

 original headquarters were probably in some northern or circum- 

 polar land, which enjoyed a warm and equable climate. 



