XIV 



The Record of the Rocks 269 



Archaeopteryx, the first bird-like creature, appears in the 

 Jurassic period. The Cretaceous or chalky rocks are 

 largely composed of solidified globigerina oozes, and in- 

 numerable shell-bearing sea creatures occur amongst them. 

 Fishes like the herring and salmon appear for the first 

 time, and huge reptiles and birds with teeth were common. 

 Traces of the flowering plants also appear amongst the 

 prevailing ferns. 



350. Tertiary Rocks. A great gap generally separates 

 the period of the Mesozoic rocks from that of the Cainozoic 

 or Tertiary. During the interregnum the great reptiles and 

 ammonites became extinct, and forms of life appeared more 

 closely resembling those of the present day. The divisions 

 of tertiary rocks Eocene, Oligocene, Miocene, and Pliocene 

 were originally arranged in the order of the abundance of 

 the fossils of mollusca, resembling those now existing. As 

 the period progressed plants and animals which approached 

 more and more closely to those we now know appeared on 

 the Earth. Foraminifera attained a great size and were 

 extremely numerous, one being the large coin -shaped 

 nummulite which makes up many of the limestones. Mol- 

 lusca like the oyster and snail began to predominate over 

 those of the cuttle-fish kind. Amongst the mammals the 

 marsupials became less numerous, and many transition 

 forms of the Eocene approach the carnivorous type. Later, 

 gigantic ant - eaters, the elephant - like Mastodon, pig- 

 like animals, antelopes, and apes appeared. A succession 

 of animals of increasing size, approaching nearer and nearer 

 the nature of the horse, runs through the series, culminating 

 in the true horses of the Pliocene age. The fossils of these 

 large animals are never so complete as those of mollusca or 

 ferns, some teeth, or a few shattered bones, being all that 

 is usually found. The Tertiary period was characterised by 

 great volcanic activity in all parts of the world, and the 

 existing scenery of many lands is due to the effects of 

 denudation on the basalt sheets and lava dykes of the old 

 volcanoes. 



351. Quaternary Rocks. The post-Tertiary or Quater- 

 nary rocks are the least ancient of all. They are rarely 



