96 PHILOSOPHY OF ZOOLOGY. 



In reference to this view of the subject, we may add, 

 that the laws which regulate the distribution of recent 

 animals, have been, in a great measure, deduced from ob- 

 servations on those which inliabit the countries between the 

 Tropic of Cancer and the Arctic Circle ; so that we have 

 much to learn with regard to the characters of those which 

 dwell between the Antarctic Circle and the Tropic of Capri- 

 corn. But the observations on the distribution of the fossil 

 species, from having been chiefly carried on in the middle 

 and south of Europe, are more confined. A vast number of 

 fossil species, therefore, remain unexplored in the equato- 

 rial and antarctic regions, the characters of which will ei- 

 ther confirm the view which is here given, or furnish evi- 

 dence for that alteration of climate, occasioned by a change 

 in the obliquity of the ecliptic, or in the Earth"'s axis of ro- 

 tation, which a few naturalists believe to have taken place. 

 If the fossil animals at the Equator do not resemble recent 

 or fossil Arctic productions but exhibit characters peculiar 

 to themselves, it will be necessary to abandon the idea of 

 great astronomical revolutions, and content ourselves with 

 investigating the changes organised beings are experiencing 

 at present, in order to discover those circumstances which 

 have impressed on the fossil species their peculiar outland- 

 ish character. 



3. The opinion entertained by Weiiner, that the petri- 

 factions of the older rocks, belong to animals of more simple 

 structure and less perfect organization, than those which occur 

 in the recent deposits, is, when considered in a very general 



much from those of another, as the recent kinds are known to do, so that 

 every country will have its fossil, as well as its recent testacea. Few obser- 

 vations illustrative of this branch of the subject have hitherto been pub- 

 lished." Mr Greenough has since combated the same opinion, in his «' Cri- 

 tical Examination of the First Principles of Geology,"— London 1819, 

 p. 287. 



