PREFACE. 



This paper is the second of the series upon the vertebrate fauna of the Permian 

 or Permo-Carboniferous beds of North America. The first, "A Revision of the 

 Pelycosauria of North America," appeared as publication No. 55 of the Carnegie 

 Institution of Washington, in 1907. The third, "A Revision of the Amphibia and 

 Pisces of the Permian of North America," will follow shortly. 



Much doubt has recently been cast upon the true Permian age of the Red Beds 

 in Texas, where the fauna is most abundantly represented. Evidence has been 

 brought forward to show that these beds and the fauna in them (which is also present 

 in other parts of the continent) must be referred, in part at least, to the Pennsyl- 

 vanian age. The name Permian has been retained provisionally in the title until 

 more complete evidence has been gathered. It is hoped that a fourth volume of 

 this series may be completed, gathering together the evidence as to the age of this 

 fauna, its relations to its surroundings, and its origin and final distribution over the 

 world. 



In this place, I desire to express my thanks to the Carnegie Institution of 

 Washington for its continued support. 



To the authorities of the American Museum of Natural History in New York 

 I am greatly indebted for their kindness in permitting me to study the type material 

 there preserved and to publish illustrations and descriptions of their material. 

 Especially am I under obligation to President H. F. Osborn and to Dr. W. D. 

 Matthew for advice and assistance in the work. 



Both Dr. S. W. Williston, of the University of Chicago, and Dr. Richard Broom, 

 of Springs, South Africa, have been of great assistance to me in the preparation of 

 the manuscript. 



Finally, I must express my thanks to Mr. Erwin Christman, without whose 



painstaking care in preparing the illustrations, both this and the forthcoming volume 



would have lost much in value. 



E. C. Case. 



