INTRODUCTION. 



the conditions under which they Hved and developed may properly be 

 offered as a part of the series and for the same purpose — to form a basis for 

 future work. 



From evidence furnished in the body of this work the author is convinced 

 that there were two large areas of Red Bed deposition in western North 

 America near the close of the Paleozoic. One may be referred to as the 

 Plains Province; it included the western portions of Texas, Oklahoma, 

 Kansas, Nebraska, and southwestern South Dakota and the portions of 

 Wyoming, Colorado, and New Mexico east of the Rocky Mountain Front 

 Ranges ; that this area extended far to the north, even into Canada, there is 

 some evidence, but the limits of the northern portion can not yet be stated. 

 The other area, referred to as the Basin Province, can not be so clearly 

 outlined as the first, but from the combined evidence of vertebrate and 

 invertebrate fossils it is apparent that there was an area of Red Bed deposi- 

 tion west of the Rocky Mountain Front ranges, extending from the Colorado 

 Canyon through western New Mexico, western Colorado, Utah, and Wyo- 

 ming. Whether this area also extended farther to the north is not known. 

 The extent of these areas is shown on the map opposite page 88, plate 4. 



It is not the intention of the author to maintain that deposition in the 

 two areas was contemporaneous ; in fact, there is some reason to believe that 

 the western area received its deposits somewhat earlier than the eastern, 

 but this matter also remains to be decided. 



Vertebrate fossils of Permo-Carboniferous age have been found in five 

 localities in North America : (i ) In an area in Texas, Oklahoma, and Kansas, 

 a portion of the Plains Province; (2) in north-central New Mexico, a portion 

 of the Basin Province; (3) in east-central Illinois; (4) in western Pennsyl- 

 vania; (5) in Prince Edward Island, Canada. 



The author desires to repeat the thanks, expressed in previous publica- 

 tions, to the Carnegie Institution of Washington and its officers, for the 

 aid and encouragement which has enabled him to carry thus far a research, 

 which has involved no small amount of time and labor. 



