FORMER SHORES OF THE TERTIARY SEA—CHICO CREEK STRATA. 
173 
the current, although, in many respects, the bed appeared like a beach accumulation. The 
valves were broken and separated, and piled in confusion, one on another, the interstices being 
filled with coarse sand. The shells could not, however, have been rolled on the beach or trans¬ 
ported about in contact with gravel and sand for a very long period, as the perfection of the 
moulds of the outer parts was such as to lead to the belief that they had not been long exposed 
to attrition. 
The proximity of these beds to the high ridges of the Sierra Nevada, and to the underlying 
granitic and metamorphic rocks, render the presence of beach accumulations extremely probable. 
They would, in most cases, become re-assorted and drifted to a short distance during a period of 
subsidence, especially if attended by sudden or convulsive movements. 
We should expect to find, also, at dilferent points along this belt of Tertiary strata, the 
evidences of the former flow of rivers from the mountains as at the present day. Indeed, it is 
most probable that the great mass of the strata is composed of materials transported to the 
former sea by the rivers of the Sierra. At the points where these rivers were most numerous 
and powerful, we should expect to find great variations in the lithological characters of the 
strata, and also the remains of land plants and animals. The layers of charcoal which occur, 
may have been, and probably were, brought down to the sea by rivers. These little fragments 
not only show the presence of adjoining dry land covered with vegetation at that distant period, 
when the whole inhabitable part of California was submerged beneath a Tertiary sea, but they, 
together with the volcanic ashes in which they are entombed, assure us of then existing 
volcanoes, in full activity, sending out streams of lava and producing conflagrations in forests 
long since passed away. 
The remains of marine mollusca and of sharks are now about one hundred miles distant from 
the ocean, and separated from it by high mountains. The bed of shells is at an elevation of 
750 feet above tide, and the shark’s teeth were at least 1,200 feet. It is probable, however, 
that at other localities similar remains will be found at a much greater elevation; the hills upon 
which the teeth were found being much lower than many within a short distance. There is 
little doubt that in a few years, when the country becomes settled, and it is possible to roam 
over the hills of this formation at leisure, many important localities of organic remains will be 
found, and that it will become a favorite resort for the palaeontologist. 
CHICO CREEK AND VOLCANO RIDGE—VALLEY OF THE SACRAMENTO. 
A very interesting deposit of fossil shells occurs on Chico creek, in the valley of the Sacra¬ 
mento, at the foot-hills of the Sierra Nevada. This was brought to notice by Dr. Trask in his 
reports, and he presented me with a specimen of the rock. It is a compact calcareous sand¬ 
stone, very hard, and of a gray color. The fossils are well preserved, and are white. Most 
of them are fragments, and many species are thickly mingled together. The single specimen con¬ 
tains a Nucula , N. divaricata, Conrad, Madra albaria, Conrad, Tellina ——, [?] Natica -[?] 
and fragments of spiral shells. There are also fragments of Dentalium and small Bacuities. 
The occurrence of the latter in this deposit is exceedingly interesting, and was first announced 
hy Dr. Trask. Three fragments can be recognized in the specimen I obtained. They are 
partly exposed, and are about one-quarter of an inch in diameter, but the suture lines are very 
distinct. 
An interesting deposit of fossils, or rather of their casts, (for all the lime has been removed,) 
