26 THE PALEONTOLOGIC RECORD 



faunas in which few of the genera and none of the species are identical 

 with those now living the problem becomes more difficult and the con- 

 clusions are much less definite, as the comparisons must be more gen- 

 eral. Proofs of actual temperatures as measured in degrees should not 

 be expected unless the botanists can furnish data. There is, however, 

 great local differentiation of faunas and it is fair to ask the question 

 to what extent this is due to differences in climate. One of the earliest 

 discussions of this question was by Ferdinand Roemer, who more than 

 fifty years ago in " Die Kreidebildungen von Texas " noted the fact 

 that the Cretaceous of the highlands in Texas is lithologically and 

 faunally much like the Cretaceous of southern Europe and the Medi- 

 terranean region, that it differs from the Cretaceous of New Jersey in 

 about the same way that the southern European Cretaceous differs from 

 that of England and northwestern Germany, and that in each case the 

 European deposit is approximately 10 farther north than its American 

 analogue. He concluded that the differences between the northern and 

 southern facies were due to climate and that the climatic relations be- 

 tween the two sides of the Atlantic were about the same in Cretaceous 

 time as they are now. Roemer's conclusion that there were climatic 

 zones in the Cretaceous may be true, but his reasoning was based on 

 false premises so far as the American deposits are concerned, for the 

 New Jersey type of marine Cretaceous extends with little change all 

 the way from New Jersey to the Rio Grande, and the " Cretaceous of 

 the highlands " with which he contrasted it, now known as the 

 Comanche series, is not represented by marine beds on the Atlantic 

 coast. This shows the necessity for careful stratigraphic and areal 

 work as well as for good paleontology before such broad conclusions 

 can be safely made. 



The more general work of Neumayr 2 recognized in the Jurassic 

 and Cretaceous of Europe three fauna! provinces designated as boreal, 

 central European, and alpine or equatorial, which on account of their 

 zonal distribution he regarded as indicating climatic differences. He 

 believed that these zones are recognizable throughout the northern 

 hemisphere and cited evidence to show that similar zones exist south of 

 the equator. In recent years Neumayr's conclusions have been ques- 

 tioned by many because in so many instances genera supposed to be 

 characteristic of one zone have been found mingled with those of 

 another. For example, the alpine ammonite genera Lytoceras and 

 Phylloceras occur in Alaska (lat. 60) associated with the boreal 

 Aucella, and Aucella itself ranges from the Arctic Ocean to the torrid 

 zone. Still, in spite of such exceptions and anomalies in distribution, 

 there is much evidence for a real distinction between boreal and south- 

 ern faunas in the Jurassic and in the Cretaceous which may indicate 

 a zonal distribution of temperature in Mesozoic time. It should be 



2 " Erdgeschichte," Vol. II., p. 330 et seq. 



