Xll PREFACE. 



age in Nevada was first made known by the Geological Sur- 

 vey, in the Proceedings of the California Academy (see Vol. 

 Ill, p. 307) in 1866. Previous to that, in May of the same 

 year, a synopsis of what was known in regard to the age of 

 the stratified rocks of Nevada, was communicated to the 

 same Academy (see Proceedings, Vol. Ill, p. 266). The 

 collections received from Nevada at various times, together 

 with the results obtained by myself in three visits to the 

 State, and the important work of Mr. Gabb and party in 

 1867, have given us a pretty good idea of the geological 

 structure of Western and Southwestern Nevada. The " Sur- 

 vey of the 40th Parallel," organized by the U. S. Engineer 

 Office in 1868, and placed in charge of Mr. C. King, formerly 

 of the California Survey, will give us a large amount of de- 

 tailed and reliable information in regard to the northern and 

 eastern portions of the State, and it only remains to work up 

 the southeastern corner, a very interesting region, but one 

 difficult of exploration. To this part of the State I had 

 hoped to be able to send a party during the summer of 1868; 

 but circumstances have rendered it impossible for me to carry 

 out my plans. 



At the meeting of the National Academy of Sciences, held 

 at Northampton, in August last, Mr. Gabb read a paper giv- 

 ing the results obtained by himself in working over the col- 

 lections of the Geological Survey, in reference to the subdi- 

 visions and paloeontological relations of the Cretaceous and 

 Tertiary rocks of California. In this paper Mr. Gabb pro- 

 poses a new division of the Cretaceous of the Pacific coast, 

 which is referred to in the body of the present volume, and 

 the leading features of which may here be succinctly stated. 



The Cretaceous formation is found covering large areas on 

 the West Coast, from Vancouver and the adjacent islands of 



