98 J. Arthur Phillips — On Silicified Woods of California. 



fully twice the size of the largest Bostellaria yet known from the 

 Ganlt. 



Tn my opinion, as well as that of many of my geological friends 

 who have done me the honour of examining this fossil, it is quite a 

 new species, and as such I propose to name it Bostellaria maxima, 

 that being the most appropriate designation I can apply to it. 



II. — Note on the Silicified Woods of Califoknia. 

 By J. Arthur Phillips, M.Inst.C.E., F.G.S., F.C.S. 



THE deep placers of California are often covered by a thick cap- 

 ping of lava ; in other places, the eruptive matter overlying 

 the auriferous gravels occurs in the form of columnar basalt, 

 beneath which is found the auriferous strata of sand, clay, and 

 gravel. These deposits often contain immense numbers of large 

 tree-trunks, which, with those portions of their branches which 

 remain, are either silicified, or are converted into a lignite, often 

 containing a considerable amount of iron pyrites. 



Many of these trees bear unmistakable marks of having been 

 exposed to the action of violent currents before becoming embedded 

 in the detritus which now covers them, and fragments are some- 

 times met with, of which one portion had become more or less com- 

 pletely converted into lignite previously to silicification. In such 

 cases, specimens may be obtained having the appearance of jet and 

 opal respectively ; each portion distinctly retaining the original 

 structure of the wood. 



In these sedimentary deposits, leaf-beds and impressions of leaves 

 are of not nnfrequent occurrence, and from a preliminary examina- 

 tion of these, by Dr. Newberry, they are believed to be of Tertiary 

 age ; probably belonging to the later Pliocene epoch.^ 



In order to determine the difference in composition existing 

 between silicified wood and silicified lignite, the following analyses 

 were made : — 





Silicified Wood, 

 sp. gr. 204. 



Silicified lignite, 

 sp. gr. 1-95. 



Silica 



I. 

 92-43 

 trace 

 •90 

 •12 

 •41 

 •20 



1-87 

 3 90 



II. 



92-26 

 trace 

 •88 

 -18 

 -37 

 •18 



1-90 

 3-90 



I. 



80-04 



trace 



-92 



•16 



•37 



-20 



14-06 



1-49 



2-92 



II. 



79-82 



trace 



-87 



•16 



•30 



•22 



13-92 



1-54 



2-92 



Alumina 



Ferrous Oxide 



Lime 



Potassa 



Soda 



Carbonaceous matter 



■rrr , ( ComMued 



water 1 Hygroscopic 



99-83 



99-67 



100-16 



99-75 



Both specimens were obtained from the trunk of the same tree, 

 found in the auriferous drift under a volcanic capping, near Nevada 

 ^ Geological Survey of California, pp. 250-251. 



