Californian Metamorphic Formations. — Hcrshey. 233 
but also to their representing the older or Devonian portion 
of the series. 
This series of slates, quartzytes and limestones certainly 
represents in part the Calaveras formation of the Sierra Ne- 
vada region, but also seems to include strata of the same age as 
the Arlington and Robinson formations. The Devonian por- 
tion of the series is not well represented in the Sierra Nevada 
region, but strata of that age have been discriminated there. 
I should be inclined to extend the term Calaveras in its original 
significance to the Klamath region if it had not come to be 
restricted to a particular portion of the Devono-Carboniferous 
series. It is doubtful if we shall be able to separate the Devon- 
ian and Carboniferous components of the series in the south- 
western Siskiyon and Trinit}'- areas, and we may be obliged to 
adopt a collective name synonymous with that which I have 
used, the Lower Slate series. 
The thickness of the series in any one section is not known 
to me. Usually the succession of strata is repeated several 
times in a single area by faulting and folding. It appears to 
be considerably thicker than the schist series and than the later 
Mesozoic slates, and an estimated average for the entire terri- 
tory of 5,000 feet is probably sufficiently accurate for the 
present. 
The Clear Creek greenstone. — Southeast of the high rugged 
peaks constituting the Sierra Costa range, there is a much 
lower mountain country constituting the basin of Trinity river 
between Trinity Center and Lewiston, the Trinity mountain 
and the ridges eastward to the Sacramento river. The geolo- 
gy of this extensive territory is comparatively simple and en- 
tirely unlike that of the country to the west. Aside from the 
intrusive granites and porphyries, the mountains are made up 
of two formations, the Clear creek greenstone and the Bragdon 
slates. The former is the foundation rock of the region and 
upon it the slates have been deposited. 
In general, the slate formation remains practicallv in its 
original horizontal position except that it has been thrown into 
a broad, shallow syncline, with an axis a few miles east 
of the summit of the Trinity range; but, considered in detail, 
it is much disturbed by faults and folds of small dimensions 
so that locally it presents dips of high degree, in not a few 
