X PREFACE. 



the year an exploration of the southern Coast Ranges, partly 

 with the view of completing the palgeontological collections 

 in the Tertiary groups, and partly with the intention of 

 working up the geology of the region, in which, at that time, 

 a large amount of money was being expended for the purpose 

 of ascertaining the value of the bituminous materials occur- 

 ring there. This party continued in the field from January 

 to June, adding largely to our knowledge of the geology of 

 Los Angeles, Santa Barbara, and San Luis Obispo counties, 

 and to our collection of Tertiary fossils. 



Mr. Gabb continued his work northward from the Bay of 

 San Francisco, accompanied by Mr. F. Coffee, during the 

 months from July to November, and explored a large por- 

 tion of Sonoma, Mendocino, and Humboldt counties, a 

 region of sedimentary rocks, chiefly of Cretaceous age, but 

 not rich in fossils. 



A party was at work during this summer in the High 

 Sierra, in Mariposa and Tuolumne counties, under the 

 charge of Mr. King; but their operations Avere exclusively 

 confined to a region of granitic and volcanic rocks, and no 

 additions were made by them to our palaBontological ma- 

 terials. 



Another party, under my own charge, in Plumas County, 

 during the same summer, made a pretty careful exploration 

 of the fossiliferous localities around Genesee Valley, and col- 

 lected some new species. They were not successful, how- 

 ever, in finding, in Plumas County, any new localities of im- 

 portance, although the region was pretty carefully examined. 

 A party, under Mr. D'Heureuse, was also in the field during 

 the summer of 1866, in Kern County, but not in a fossilifer- 

 ous region. 



In 1867 there was no work done in the fossiliferous forma- 



