PREFACE. XI 



Region, and from the auriferous rocks of the Sierra Nevada. 

 Mr. R. Homfray kindly presented us with a valuable suite 

 of fossils from Nevada Territory. Mr. Remond has given 

 the Survey the use of his collections, made chiefly in the 

 vicinity of San Francisco Bay, previous to his joining our 

 corps. Dr. George H. Horn, U.S.A., who was stationed at 

 Fort Tejon for several months, collected assiduously in that 

 prolific locality of Cretaceous fossils, and kindly placed all 

 his materials at Mr. Gabb's disposal. Mr. E. Mathewson has 

 collected with great zeal in the prolific localities around 

 Martinez, and has generously furnished the Survey with 

 specimens of all such species found by him as were not 

 already in our possession. Other persons have contributed 

 one or more specimens each, some of which, belonging to the 

 larger mammalia, are of considerable value : these will be 

 noted in the volume in which they will be described, and 

 due credit given to the persons by whom they were pre- 

 sented. 



As the general plan of operations of the Survey, and 

 the progress made in each department up to the present 

 time, will be fully set forth in the volume of Geology, which 

 will soon follow this, it will only be necessary here to give 

 such a sketch of the extent and order of our field-work as 

 may be necessary to enable those consulting this volume to 

 understand what parts of the State and the adjacent Terri- 

 tories we have visited, and what districts are represented 

 by the materials elaborated in this portion of the Report. 



During the winter of 1860-61, the field-work having com- 

 menced December 12, 1860, we explored San Bernardino 



