PREFATORY NOTE. 



The Carnegie Institution of Washington has already published several mono- 

 graphs upon paleobiological subjects, written by its research associates, Hay, 

 Wieland, and Case. Each author has dealt with the subject-matter of his particular 

 field, but each has brought to bear upon his work common factors which have 

 placed his labors upon a broader basis than the mere morphological descriptions 

 of fossil forms of life. Case has published four monographs upon the morphology 

 and taxonomy of the Permo-Carboniferous vertebrates of North America, and 

 has followed these by a fifth, in which all the known factors bearing upon the 

 development of the life were assembled in an effort to discuss the paleogeography 

 of the period. In his conception paleogeography is a very broad term, involving 

 not only a study of the distribution of land, water, and life in any one interval of 

 time, but a consideration of all the factors in the extremely complex inter-rela- 

 tions of organic and inorganic matter and causes which influence the development 

 of each part. 



Geologists and paleobiologists have alike suffered in their interpretation of 

 past conditions, because of their lack of knowledge of the work done by others. 

 Stratigraphy may not be interpreted from the preserved fossils without a knowledge 

 of biological laws, and the formations of the earth may not safely be rearranged 

 to account for the present or past distribution of life without a knowledge of geo- 

 logical processes. 



It is obvious that such work is beyond the possibilities of any one man; it is 

 rather the work of a group of men, each broadly trained and each master of his 

 own field and able to contribute to and criticize the work of his fellows. Nowhere 

 could close cooperation of this kind be better accomplished than under a system 

 such as the Carnegie Institution of Washington has developed, whereby the research 

 associates of the Institution and others of its staff may call in the assistance of 

 men in related fields. Already the value of this procedure is apparent in the results 

 accomplished by cooperation. 



The following monograph, by Dr. Roy L. Moodie, adds an important link to 

 the series of paleobiological publications of the Institution and is closely connected 

 with the work already done upon the Permo-Carboniferous vertebrates, since it 

 supplies a description of the life of the period immediately preceding. It is hoped 

 that the volume will contribute in no small measure to an understanding of the 

 broader problems of paleogeography and the recognition of the mutual problems 

 of the paleobiologists and the geologists. 



E. C. CASE. 

 UNIVERSITY OF MICHIGAN, March ij, 1916. 



