396 HVEOS JO WIKINAUE, (QUE (GAB QIL(OXG, NZ, 
probably Danwopsis marantacea, another Rhetic plant. It shows the nerva- 
tion and basal portion of several pinnules attached to the rachis. 
There are probably three different ferns, but they are so few and in such 
small fragments of the terminal portions of ultimate pinne, that nothing of 
their true nature can be made out. It is impossible to say if they are Triassic 
or Jurassic. They have rather more of a Jurassic than a Triassic facies. 
Taking all the evidence, I think it can be positively said that ¢izs flora ts 
not older than the uppermost Trias, and not younger than the Oolite. \ feel 
pretty sure that it is true Rhetic, somewhat younger than the Los Bronces 
flora of Newberry, and the Virginia Mesozoic coal strata. It is much like the 
Rhetic flora of France, made known by Saporta. At any rate, this zs a@ new 
grouping of plants that certainly deserves to be carefully collected. I do not 
think the fossils now in hand suffice to fix narrowly the age, which may be 
Lower Jurassic. 
| 
Siene a SDE 29° N 
“mapnesian qP Ee a lewal 
limest. series. 
Fic. 2. Section across the Sierra Buttes. Horizontal and vertical scale one mile 
to the inch. qp=quartz-porphyry. qb—=quartz-porphyry breccia. at=augitic tuffs. 
M=Milton series. ss=siliceous schist. 
» On the east slope of the Sierra Buttes ( Downieville atlas 
sheet) the rocks are magnificently exposed through glacial 
agency, and during the past season the writer obtained evidence 
there of the succession (see Fig. 2) of the old volcanic rocks 
which form the larger part of the Buttes. 
Forming the mass of the Buttes is a fine-grained rock contain- 
ing abundant porphyritic quartzes. No analysis has been made of 
the Sierra Buttes rock, but from the north end of the same area, 
which extends to Eureka Peak, three specimens were collected 
and analyzed,’ giving the following results : 
™ Fourteenth An. Rep. U. S. Geol. Survey, p. 473. 
