XIV PREFACE. 



Bay of San Francisco was more thoroughly examined by 

 small parties on foot, especially portions of Santa Clara, 

 Contra Costa, and Alameda counties. During this season 

 the larger portion of the Cretaceous fossils described in this 

 volume were collected, a large number of the most prolific 

 localities having been discovered in the course of the sum- 

 mer. The Carboniferous limestones of the Sierra Nevada, 

 from Pence's ranch north to Bass's ranch, were also carefully 

 examined during this season, and the collections made which 

 are reported on by Mr. Meek in this volume. 



During the season of 1862, we were fortunate enough to 

 secure Triassic fossils from several different portions of the 

 Territory of Nevada, especially a valuable collection made 

 by Gorham Blake, Esq., in the Humboldt Mining Region. 



In 1863, the region about Fort Tejon, the Canada de las 

 Uvas, and that portion of the State which lies about the 

 head-waters of the San Joaquin, was made the object of a 

 reconnoissance by Messrs. Brewer and Gabb. and a conside- 

 rable number of new Cretaceous species discovered. After 

 this was accomplished, the work of the Survey was, during 

 the remainder of the season, mainly confined to the high 

 Sierra, and consequently but little was added to our stock of 

 fossils. In September, however, Messrs. Brewer and King 

 made the interesting discovery of a locality of Triassic, and 

 also one of Jurassic fossils, in and near Genessee Valley, in 

 Plumas County ; the latter constitute the material worked up 

 by Mr. Meek in Section III, of this volume. The Triassic 

 fossils from Genessee Valley, together with those collected by 

 Mr. G. Blake, and by the Survey as previously noticed, and 



