ANCIENT CLIMATE AND PALEOCEth ;RA Y. 1 li math- zones are thought to have existed as early as Cambrian time and to have continued through the Silurian and Devonian periods. The Euro and North American fauna. of these pe riods can be separated into northern and southern types which are quite distinct, the various genera having representative spceies in eavh zone. The conrses of oeeaMe currents have been indicated for the -arty :Ind late Ordovieian by Matthew and IZuedetnann. other evidence regarding the climate of the Paleozoic is derived from study of the of the fossil coral reefs of the Silurian. and of the plants of the Carboniferous. The Silurian coral reefs are found in high lati tildes and indicate rather warm temperatores for those regions, and the structure of the Coa• boniferons tree trunks points to a remarkable uni formity of the seasons (luring that period. Neu. move bins tried to demonstrate that the Jurassic aid Cretaceous faunas show the iniluenee of N‘(.11 marked climatic zone: which extended in around the globe independent of the continental barriers. hut his result: have not been eonfirn ed
by subsequent investigations. During the Ter tiary, lume%er, climatic zones certainly exi,ted, as is indicated by the fossil floras and faunas, but a lowering of the temperature began during Emetic tune in North America and during Mio cene time in Europe. and culminated in the ice age of the Pleistocene. Various interesting at tempts have been made by Neumayr, Chamberlin, and others to correlate the evolu tion of animals and plants with the changes of climate in past times.
It will be seen from what has been said re garding faeies development that the study of the distribution and migration of fossil faunas leads to conclusions regarding the physical geography, pale(,geography, of ancient times; these conclu sions most of course be tested in the light of the evidence derived from the study of the tectonic features. Much has been accomplished in this fold of research by Ileer. Neumayr, Suess, De Lapparent. Cann, Smith. Chamberlin, Weller, Ortmann, Schuehert. Ulrich. and Clarke.