170 DISTRIBUTION OF EXTINCT ANIMALS. [part n. 



Distribution of Land Animals ; and however imperfectly the task 

 has been performed, the reader will at all events have been con- 

 vinced that some such preliminary investigation is an essential 

 and most important part of our work. So much of palaiontology 

 is at present tentative and conjectural, that in combining the 

 information derived from numerous writers, many errors of detail 

 must have been made. The main conclusions have, however, been 

 drawn from as large a basis of facts as possible ; and although 

 fresh discoveries may show that our views as to the past history 

 of some of the less important genera or families are erroneous, 

 they can hardly invalidate our results to any important degree, 

 either as regards the intercommunications between separate 

 regions in the various geological epochs, or as to the centres 

 from which some of the more important groups have been dis- 

 persed. 



