12 BRITISH MAMMALS 



(creodonts, seals, dogs, cats, bears, etc.) ; (7) the Rodents 

 (squirrels, rats, hares, etc.) ; (8) the Insectivores (moles, 

 hedgehogs, shrews, and their allies) ; (9) the Eats ; (10) the 

 Primates (lemurs, monkeys, man). The term " order " is 

 of somewhat varying signification in these groupings, but in 

 a work of this description it is unnecessary to discriminate 

 too closely. 



The history of mammalian distribution over the British 

 Islands, and the relations of that colonisation with the great areas 

 of mammalian development in the world at large may be 

 summarised as follows : It is possible that the Mammalia as 

 a class originated in North America 1 or in some region round the 

 North Pole. During the early part of the Secondary Epoch, the 

 backbone of Britain, that is to say, the mountainous regions of 

 Scotland, Wales, and Ireland, possibly formed an outlying 

 peninsula of the North American continent, and from that 

 direction came the first primitive types of monotreme, mar- 

 supial, and early Eutherian, remains of which are found in 

 British formations of the Secondary Epoch. No doubt at this 

 time Britain may have been a link connecting the Old World 

 with the New in the Northern Hemisphere, whilst South America 

 was connected through Antarctica with Australia, and later, in 

 equatorial regions, with Africa. This connection of Britain with 

 the Western Hemisphere no doubt ceased to a great extent 

 before the Tertiary Epoch. 2 During the Tertiary Epoch, Scot- 

 land and Ireland seem to have been but little favoured in 

 mammalian distribution, whilst England and Wales (connected 

 then with the European continent) shared to a considerable 

 extent in the great mammalian developments of France, Germany, 

 and the Mediterranean regions. 



1 On the other hand, it is equally possible that they may have grown out 

 of Theriodont reptiles in South Africa. But hitherto the remains of the most 

 primitive mammals the earliest known in geological time have only been 

 obtained in North America and in England. 



2 Except for the northern link by way of Iceland and Greenland, which 

 (especially when reinforced by ice-floes in the Glacial periods) may have 

 enabled a few northern forms to reach Britain from Arctic America. 



