PEEFACE. VII 



perhaps the last work done by Mr. Marvine ; at the time he was in very 

 ill health, and a few days after sank into a condition from which he never 

 recovered, and we now have to mourn the loss of a conscientious, able, and 

 vigorous geologist, and it is with profound sorrow that I am compelled in 

 acknowledging his courtesy to record his death. 



Mr. J. C. Pilling, for the past three years, has traveled with me as 

 stenographer an 4 assistant geologist, and to him I am indebted for the col- 

 lection of a great body of details of diverse character, but especially in the 

 measurement of many sections. 



Mr. W. Cleburn, one of the engineers of the Union Pacific Railroad, 

 and who has been engaged in that work for many years, has at the same 

 time interested himself in the geology and paleontology of the region, and 

 to him I am indebted for many favors, and especially for the use of his 

 valuable collection of fossils. 



To many of the citizens of the region I am indebted for courtesy and 

 substantial favors, but especially to Capt. Pardon Dodds, of the Uinta Val- 

 ley, and Mr. S. I. Field, of Green River Station. 



J. W. P. 



The following note from Professor White is inserted: 



DEAR SIR : Since my report, comprising Chapter III of this volume, 

 was put in type, further investigation of the fossils collected from the Canon 

 of Desolation has led me to doubt the correctness of the reference I have 

 there made of them to the Point of Rocks Group. It now seems probable 

 that they properly belong to the Bitter Creek Group, notwithstanding the 

 close relationship of two or three of the species with some of those found in 

 strata that are still referred without doubt to the Point of Rocks Group. 



Further collections and investigations in the field will, however, be 

 necessary before this question can be definitely settled. 

 Very truly yours, 



G. A. WHITE. 



Prof. J. W. POWELL. 



