22 THE BRITISH NATURE BOOK 



of the most probable of scientific theories. In the Secondary Epoch,* Great 

 Britain, instead of being an island, was probably a peninsula attached to the 

 North American continent, and from that direction there came the first primi- 

 tive types of some of the mammals. In the ages that succeeded, the British 

 Isles became disconnected from the Western Hemisphere as the great oceans 

 were formed, though they were connected for a time with Northern Europe, 

 till finally separated by the shallow sea we now call the Channel. So, in 

 the Tertiary Epoch, Britain received its mammals from Europe ; and as the 

 North of Europe, together with Scotland, Ireland, and much of Wales, was 

 at the close of the Tertiary Epoch under ice, the chief mammals were found 

 in the South of England, and, as has been discovered, hi East Anglia, at that 

 time joined to Holland and Belgium. 



It is known, from remains that have been discovered, that at least 113 

 different species inhabited the British Isles from the end of the Pliocene Period 

 onwards ; but of their descendants only seventy are now to be found, and 

 of these at least fifteen are so rare that they need not be counted. The total 

 number of species within British confines is fifty-seven. 



Order: CETACEA Whales and Porpoises. 



The Whales are easily the largest of British mammals, t They were origin- 

 ally land animals, which have become completely adapted to living in water. 



* The following are the great epochs into which geologists have divided the past history of 

 the world : 



SECONDARY. The Triassic Period, in which the first Reptiles (Anomodontia) and a few 

 Mammals of low type began to appear. 



The Jurassic Period, when Birds began to originate from Reptiles. 



The Cretaceous, or Chalk, Period, which was the great age of Reptiles, and when, possibly, 

 some of the later types of Mammals had their first forms. 



TERTIARY. The Eocene Period (Oligocene), when many of the present-known orders of Mammals 

 were first evolved. 



The Miocene Period, in which the families of Mammals developed. 



The Pliocene Period, in which MAN originated. 



The Pleistocene Period, when many modern species were first distinguished, and Man became 

 established in Great Britain. 



QUATERNARY. The Prehistoric Period, in which Neolithic Man lived, and most of our domestic 

 beasts originated. 



The Recent Period, from somewhere about 7000 B.C. to the present time. 



t The following is a list of all the orders of mammals to be found in Great Britain : 



Ungulata : Single-hoofed mammals example, the Horse. 



Ruminantia : Cud chewers Deer, Cow, Sheep. 



Cetacea : Whale-like, including Porpoises and Dolphins. 



Pinnipedia : Fin-footed the Seal. 



Carnivora : Flesh-eating Weasel, Stoat, Cat, Dog, etc. 



Rodentia : Gnawing mammals Rat, Rabbit, Squirrel. 



Insectivora : Insect -eating mammals Shrew, Hedgehog, Mole. 



Cheiroptera : Hand-winged the Bats. 



Primates : " Highest " mammals Man. 



This classification is based chiefly on the character and arrangement of the teeth, but also upon 

 the form of the limbs. If you examine your own teeth, you will find that you possess three kinds: 



