80 MUSEUM OF COMPARATIVE ZOOLOGY. [Feb. 



has already convinced me of their great importance. Our knowledge 

 of the range of the natural faunae is verf imperfect, and I have found 

 it impossible to adopt, without modifications, any of the proposed 

 divisions of the earth's surface into zoological provinces. The divi- 

 sions thus far proposed show plainly that they were circumscribed by 

 physical considerations, and not by the special study of the range and 

 distribution of the animals themselves. However, by the very attempt 

 to place side by side, in a methodical order, all the representatives of 

 adjoining faunae, I have gradually been led to define more accurately the 

 natural limits of the faunae themselves. It is surprising to me that 

 the principle by which faunae may be defined has not yet been stated, 

 although it is very simple. It may thus be expressed : the geograph- 

 ical range of representative species occupying adjoining regions marks 

 the natural boundaries of their respective fauna. 



Since in our days it is no longer possible to study the animal king- 

 dom without including in the investigation the remains of past geo- 

 logical ages, the question has naturally arisen, what disposition to 

 make of the fossils. After mature consideration, I have come to the 

 conclusion, that for their most suitable arrangement it was indispen- 

 sable to make also two kinds of collections of the fossil remains. In 

 one of them, which corresponds to the systematic collection of the 

 living animals, they are arranged systematically, according to the 

 natural affinities of the different representatives of each geological 

 period, in such a manner that the zoological character of these epochs 

 is shown as distinctly to the eye of the student as the character of 

 the present creation, by the study of the systematic collection of the 

 living animals. With the aid of these collections, special zoological 

 treatises of each period may be compiled without difficulty ; and I 

 have already satisfied myself that a comparison of those collections 

 furnishes much information respecting the true affinities of animals. 



The second kind of collections of fossils is arranged in a way which 

 corresponds to the faunal collections of living animals ; that is to say, 

 according to their geographical distribution during each successive 

 geological epoch. This arrangement has enabled me to display by 

 themselves the more extensive collections of fossils, obtained from 

 particular localities, in their characteristic mode of association, without 

 crowding them upon the attention of the beginner, or giving them, 



