Reviews 



The Environment of Vertebrate Life in the Late Paleozoic of North 

 America; A Paleogeographic Study. By E. C. Case. Carnegie 

 Institution: Washington Publication No. 283, 1919. Pp.273, 

 figs. 8 and two correlation tables. 

 This publication will be welcomed by all geologists as a signal con- 

 tribution to the interpretation of conditions of the late Paleozoic. Dr. 

 Case is well qualified to summarize the conditions surrounding the verte- 

 brates, and to draw conclusions as to the influence of the environment 

 on their development and distribution. 



In the first chapter the various methods of attack and the complexity 

 of the factors in any paleogeographic problem are briefly presented. 

 There follows a summary of late Paleozoic rocks in the several prov- 

 inces of North America. For the most part the descriptions are quota- 

 tions from other writers and are not intended to present new material. 

 Quite apart from the obvious purpose, this summary will be of great 

 use to the student, gathered as it is from a voluminous hterature on 

 the subject. The selections are well made; they are representative of 

 current opinion, to the point, and show no evidence of an attempt on 

 the part of the compiler to prove a point. The full usefulness is slightly 

 impaired, perhaps, by the absence of an index. The accompanying 

 correlation tables differ little from generally accepted views. 



Contrary to what might be expected, the author makes no attempt 

 to fix the lower boundary of the Permian. Throughout the work he 

 refers repeatedly to Permo-Carboniferous times in the sense of a transi- 

 tion period between the Pennsylvanian and the closing events of the 

 Paleozoic. He makes a sharp distinction, however, between Permo- 

 Carboniferous times and Permo-Carboniferous conditions, and em- 

 phatically states that these two things are not necessarily coincident. 

 Perhaps the most important deduction reached, together with the 

 dependent conclusions, is that Permo-Carboniferous conditions pre- 

 vailed in the east, starting with Mid-Conemaugh time, and reached the 

 southwest considerably later. The deposition of red sediments is taken 

 to mark the introduction of important new climatic and physiographic 

 conditions and accompanying changes — Permo-Carboniferous condi- 



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