2 INTRODUCTION. 



English oucs to express the meaning. Por the same reason, in addition to disphiying in correlative 

 order the distribution of plants and animals throughout the globe, so that the facts may be analj'sed 

 and reasoned on, I shall make it an object to supply general information regarding the habitats of 

 those plants or animals as to which the educated reader is most likely to feel curiosity. References 

 to authorities will be given whenever they seem likely to be usefid. Every naturalist must have 

 folt the want of such references when searching for information on any subject ; and in the present 

 case they are especially necessary, for the Zoologist is often unfamiliar with Botany, the Botanist 

 with Zoology, and the specialist at sea when he gets beyond the limits of his o^Ya territory ; and 

 yet none of them can proceed far in their work without having frequent occasion to know something 

 relating to the geographical distribution of other organized beings which incidentally come in con- 

 nexion with the subject of their studies. I have endeavoured in my references to hit the medium 

 between a burthensome display of erudition, and a selection too meagre to be of use. 



It is right for me to say that I should never have ventured to undertake a work of such extended 

 scope, were it not for the promised aid and support of many naturalists eminent in those depart- 

 ments in which I am myself more especially deficient. 



To assist the non-geological reader in following any speculations in which extinct animals 

 are concerned, I have given a diagram, showing the succession of geological strata, and their 

 respective thickness. 



I have also given several maps of a general nature. The first is one representing the 

 100 fathom line of coast ; that is, the line outside of which no soundings are obtained at a depth 

 of 100 fathoms (600 feet), so that it shows what woidd be the configuration of the dry land if 

 it were everywhere raised 600 feet. I have to thank Captain Richards and the other oftieers 

 of the ITydrograiihic department of the Admiralty for the kindness and liberality with which 

 they enabled me to prepare this map, by giving me access to the charts in their possession, as 

 well as ready information on every point on which I applied to them. 



The second map represents what would be the i^robable coast-line if the whole land were 

 depressed 600 feet. It is unnecessary to say that this is much less accurate, notwithstanding 

 tliat I have had the advantage of the materials in the Geographical Society's possession. Com- 

 jiaratively few of the lower altitudes of the earth's surface are known ; it is, therefore, not to 

 be taken as more than a very conjectural approximate essay. 



A third map shows the parts of the earth on which tertiary and quaternary formations 

 have been ascertaiued to occur, that is, those which were probably imder water at the time of 

 the glacial epoch or not long previously. 



A fourth map shows, so far as known, the localities where glacier action or remains of the 

 di-ift or boulder clay have been remarked. My best thanks are due to Professor Ramsay for the 

 readiness witli whicli lie has imparted to me his copious information both on this and other subjects. 

 Nevertheless this map, too, is merely offered as a distant approximation. The importance of 

 the effects of the glacial epoch, however, renders even such an imperfect tentative very desirable 

 for the proper understanding of the questions arising out of the action of that period. 



