W. LINDGREN^F. H. KNOWLTON 



beds ; on the other hand Professor Whitney states in his volume 

 on the auriferous gravels that the matrix in which the fossils 

 occurred was rhyolitic tuff. Professor Andrew Lawson kindly 

 sent me some fragments of the matrix from the collection now 

 preserved in the University of California. They are soft gray- 

 ish to brownish compact clays which did not, under the micro- 

 scope, give any evidence of volcanic origin ; the extremely fine 

 grain, may, however, have masked their original character. This 

 much is certain that the fossils came from the uppermost bench 

 gravels, or the lowest rhyolitic tuffs and about 500 feet above 

 the bottom of the channel. 



The Independence Hill locality. — In 1891 Dr. Cooper Curtice, 

 on the request of Dr. G. F. Becker, visited many places in the 

 gold belt to collect fossils. Among these were the Washington 



Fig. I. General cross-section at Iowa Hill. 



gravel mine at Independence Hill, near Iowa Hill, Placer county. 

 Mr. J. B. Hobson, the owner of the mine, first directed our atten- 

 tion to the occurrence. A very fine and extensive collection of 

 fossil leaves was obtained. The leaves occur in a whitish or 

 bluish consolidated clay or shale which at first is soft, but on 

 exposure becomes moderately hard and brittle. This shale was 

 interbedded with gravels near the base of the 200 feet high bluff 

 produced by the hydraulic work. A glance at the section 

 (Fig. i) shows that the lower part of the bluff forms a part of 

 the bench gravels (2) which again are overlain by rhyolite tuff 

 (3) and gravels of the rhyolitic period (4). The fossils conse- 

 quently come from the uppermost gravels of the ante-volcanic 

 period. Professor Knowlton after making a careful study of this 

 collection, remarks on it as follows: "Dr. Curtice's is the first 

 large collection of plants that has been obtained from the aurif- 



