12 University of Kansas Geological Survey. 



the strictly scientific descriptions. For extended description of 

 the Upper Cretaceous horizons, the reader is referred to papers 

 by Mr. W. N. Logan and the writer in the second volume of 

 this Survey reports. 



The writer desires here to express his warmest thanks to Prof. 

 E. C. Case (K. U. '93) , of the Wisconsin Normal School, for the 

 preparation of his part on the Turtles ; to Dr. George I. Ad- 

 ams (K. U. '93) for the chapter on the Upper Cretaceous; to 

 Mr. C. E. McClung (K. U. '96), instructor in Zoology in the 

 University, for the chapter on the Microscopic Organisms of the 

 Cretaceous; and especially to Mr. W. N. Logan (K. U. '96), 

 n ow fellow of Chicago University, for the extensive work on 

 the Invertebrates. Messrs. Case, Adams and Logan were former 

 students in the department of Paleontology of the University ; 

 Mr. McClung, the writer's former assistant in Microscopic 

 Anatomy. They have all given their careful and skilled labor 

 wholly without remuneration from the state, and with but very 

 slight expense. 



All the drawings illustrating the vertebrates, save the first five 

 plates, have been made for this work under the writer's imme- 

 diate and constant supervision. For their accurac} r he is 

 alone responsible. Most of those of the Mosasaurs and part of 

 those of the Turtles have been made by Mr. Sydney Prentice 

 (K. U. '96), and thanks are due him for the fidelity, skill and 

 zeal that he has shown in their production. The plates upon 

 the skull, especially, have required an unlimited amount of 

 patience on his part to insure their accuracy. The larger part 

 of the figures illustrating the Turtles were made by Miss Mary 

 Wellman (K. U. '92), and do not need commendation. All of 

 the photographs used in the volume have been made either 

 by the writer or under his immediate direction. The illus- 

 trations for the Invertebrates have been largely copied or re- 

 drawn from previous authors. 



S. W. WILLISTON. 



