ABSTRACTS AND DISCUSSIONS OF PAPERS 415 



that possibly an older portion of the Cretaceous is represented here with no 

 equivalent in the European standard. 



Professor Schuchert stated that there is no marked change in the flora of 

 the Jurassic, and that the change occurs in the Lower Cretaceous. On the 

 other hand, the marine faunas change rapidly and at the end of the periods. 



Professor Merriam said that the Cretaceous offers one of the best examples 

 in the use of the migration of strand-lines for correlation purposes. Before 

 an adequate time classification can be established it is necessary to know more 

 of the causes of life change and of diastrophic change. More is known of life 

 changes than of diastrophic movements. 



Professor Osborn remarked that the lines drawn by Cuvier and a number 

 of other early workers were based on paleontologic evidence. The chief objec- 

 tion to the use of diastrophism for correlation purposes is that its effects have 

 not been world-wide. The continent of Africa has remained approximately 

 the same for a considerable length of time. 



Doctor Ulrich stated that the systems were originally l)ased on lithology, 

 and it was afterward recognized that they could be determined by their faunal 

 content. He cited the Silurian and Devonian as examples. The idea of world- 

 wide diastrophism depends on the meaning of the term. It refers to any move- 

 ment which will affect the strand-line. 



Professor Schuchert emphasized the world-wide influence of diastrophic 

 movement, and referred to it as due to periodic shrinking of the earth's crust. 

 The influence of diastrophism is exerted over I)oth marine and continental 

 deposits. 



Doctor Matthew stated that he believed theoretically in diastrophism as an 

 aid in correlation, but doubted its value in practical application. He recog- 

 nized the obvious evidences of world-wide diastrophism, as in the Cretaceous. 



The meeting theu adjourned. 



Session of Friday, August 6 



The mooting was oallod to order by Truf. JFenry F. Oshorn at 10 

 oV'loc'k, in Bacon ITall, room 2(m;, ITniversity of California. Tlio sym- 

 posium, "Correlation between tlie Mioceiu> of the Paoifio region and that 

 of otber areas of the woi-bl," was tbo topic of tbis session, and the morn- 

 ing was devoted to tbo reading of Ibo fullowing pajxTs: 



INTRODUCTORY /?/;iM /.'AN OY COnUET.ATJOX OF MWCKyE 



liY llKNin lAIKI' IKI.l) OSMORN 



COllRELATIOX OF TlIF LOW El! MIOCENE OF CALIFORNIA 

 MY UAI.ril AUXOI.l) 



