C. Schucliert — Evolution of Geologic Climates. 321 



have so well in hand. However, that not all of his col- 

 leagues are in harmony with his views is shown by the 

 following quotation from Wieland r 



''Does not a larger part of the Jurassic Ginkgo record also in- 

 dicate wide climatic variation, second only in extent to that of the 

 time of the Glossopteris flora ? AVonld it not be singular if plant 

 evidence remained wholly at variance from that of the insects and 

 invertebrates, indicating climatic cooling in the late Trias and 

 early Jura, not local in character?'' And A. G. Nathorst is 

 quoted by Wieland as saying that ''during the time when the 

 Ginkgophytes and Cycadophytes dominated, many of them must 

 have adapted themselves for living in cold climates also. Of this 

 I have not the least doubt. ' ' 



Knowlton knows that certain invertebrate evidence 

 which he quotes from the writer and to which Wieland in 

 the above quotation refers, indicates that toward the end 

 of Triassic time and early in the Jurassic there were win- 

 ters, about as they are now, in the latitudes of England to 

 South Germany. In this connection it may be well to 

 quote from still another paleontologist. Ulrich says :^ 



"Doubtless even in' the Paleozoic there were times of relative 

 frigidity — when some of the higher parts of the marginal lands 

 were ice-covered, in some instances attaining locally to glacial 

 conditions. Here and there regular tillites are indicated, nota- 

 bly, as recently brought out by Dr. Edwin Kirk, in the Silurian 

 deposits along the coast of Alaska." 



A careful reading of Knowlton 's paper leaves the 

 writer with the impression that the former holds that, ex- 

 cept for the early Huronian, early Permian, and world- 

 wide Pleistocene glacial times, the earth has been with- 

 out temperature zones and large arid tracts, and that in 

 general humidity has prevailed. Any paleontologist who 

 is familiar with the climatic aspects of fossils will proba- 

 bly have to agree with Knowlton that the biotic evidence, 

 and chiefly that of the floras, does in general bear out his 

 conclusion that '^climatic zoning such as we have had 

 since the beginning of the Pleistocene did not obtain in 

 the geologic ages prior to the Pleistocene.'^ But what 

 Knowlton actually holds is that there was ''a non-zonal 

 arrangement [of climate] prior to the Pleistocene'' (p. 

 541), and that the temperature of the oceans was every- 

 where the same and without ''wide-spread effect on the 

 distribution of life" (p. 548). 



' G. E. Wieland, Amer. Jour. Botany, 7, 154, 1920. 



^ E. 0. Ulrich, Jour. Washington Acad. Sci., 10, 67, 1920. 



