190 F. H. KnowUon — Evolution of Geologic Climates. 



temperature changes but slowly, there to await the return 

 of more favorable conditions. Schnchert appears to rec- 

 ognize the potency of physical causes other than temper- 

 ature in delimiting these stress-faunas, but adds: '^yet 

 the chief deterrent seemingly was the lack of proper 

 warmth.'' But this appears to be opinion unsupported 

 by corroborating facts, at least in this paper. 



The testimony of a number of well-known invertebrate 

 paleontologists may be cited on this point : 



Thus, Doctor Ulrich has already been quoted as saying 

 that the geologic marine record, from the Cambrian to 

 the Tertiary, ^'suggests equable, mild, almost subtropical 

 climates over the whole Northern Hemisphere in all the 

 ages represented." There is evidence, Ulrich adds, of 

 times when ^'frigid conditions occurred at least locally," 

 but he makes no mention of any zonal disposition of 

 temperatures. 



Dr. John M. Clarke writes that while ^Hhere is of 

 course plenty of evidence of cold weather periods and 

 also of local cold throughout Paleozoic history, I can not 

 say that such determinations are, in any single particular 

 within my knowledge, dependent upon the fossils of the 

 rocks ; nor can I say that the obvious evidences of recur- 

 rent land glaciation are connected in any way or sup- 

 ported by any facts deducible from coexistent faunas 

 and floras. ' ' 



Dr. James Perrin Smith, after discussing the range 

 of certain Triassic limestone with thick coral reefs, inter- 

 prets the evidence as indicating ''a nearly uniform 

 distribution of warm water over a great part of the 

 globe" during Triassic time. 



Dr. T. W. Stanton permits me to say that in his extensive 

 studies on the distribution of Jurassic faunas from Texas 

 to Alaska he has failed to find any indication of climatic 

 zones, and Burckhardt has had a similar experience in 

 his studies of the Jurassic faunas of northern South 

 America and Mexico, where he found a striking mixture 

 of types that should appertain to two or more of the so- 

 called climatic zones as interpreted by Neumayr. 



If it is urged that some of the above examples relate 

 to distribution in the middle portion of systems, examples 

 are not wanting of beds closing or initiating systems that 

 are likewise widespread and without e\ddence of climatic 

 zoning. Thus Doctor Ulrich directs my attention to the 



