4 INTRODUCTION. 



the only other considerable collection of Permian vertebrates from the 

 United States.* 



The fauna as represented in the various collections is very rich, con- 

 taining abundant representatives of the Pisces, Amphibia, and Reptilia. 

 The Reptilia is represented by two orders, the Cotylosmiria and the Chely- 

 dosauria^ and the suborder Pclycosatiria. The present paper has to do with 

 the last of these only, but the author hopes to discuss the other forms in 

 future papers. 



In 1904 the author received a grant from the Carnegie Institution 

 of Washington enabling him to complete the writing and illustration of 

 this monograph, which was already begun. To the authorities of the Insti- 

 tution are due his thanks for aid that permitted the work to take its present 

 form and scope. Much of the work was done at the American Museum, as 

 many of the types are presei^'ed there, where every assistance was rendered 

 the author in the preparation of material and illustrations. For this and 

 for many valuable suggestions as to the form of the work and the interpre- 

 tation of specimens, the author desires to express his hearty thanks to Dr. 

 Henry Fairfield Osborn, the curator of the department of vertebrate pale- 

 ontology, and to Dr. W. D. Matthew of the same department. 



The author is painfully aware that the following pages can lay no 

 claim to being an even approximately complete description of the Pelyco- 

 sauria ; much work, both of collection and description, remains to be done. 

 He has therefore refrained from much speculation, contenting himself with 

 the hope that he has placed the classification on a sound basis for progress 

 and has rendered the known material more available. 



* During the summer of 1906 the author made a third collection in Texas, which will go to the Amer- 

 ican Museum in New York. I have just learned that there is a small collection from Texas in the Museum 

 of Comparative Zoology at Harvard University made by Mr. Chas. Sternberg. 



