44 
FOSSILIFEROUS SANDSTONES OF THE 
this bed in the valley was 250 feet. In Panza valley, lying several miles to the east, and on 
the other slope of the granitic axis, it was found much thicker. No fossils were observed in 
either of these rocks ; hut it is probable that the upper layers may yet be found fossiliferous. 
Above these, and conformable to them, was a whitish sandstone rock, coarse in its lower layers, 
with pebbles of rounded white quartz. Calcareous fossiliferous layers occurred in the upper 
part of this sandstone, which, in places, had a dip of 35° to the southwest; the strike, north 
46° west. The total thickness of this rock is nearly 450 feet, and may be subdivided con¬ 
veniently into four beds, commencing with the most inferior. 
First bed reposes on the agatic or flinty layers described as met with at the upper end of the 
Salinas valley ; is about 200 feet thick ; a whitish sandstone grit, containing calcareous layers 
two to four feet thick ; these layers are mostly made up of ostrea titan, (Conrad,) in a condition 
tolerably perfect, cemented by a calcareous paste, the debris of the shells comminuted finely ; 
the paste includes fine grains of rounded quartz pebble. This bed of ostrea was the first one 
encountered on entering the valley where it was found, fifty yards to the left of the wagon 
road, and less than four miles north of Don Joachim’s residence. 
Second bed lies above the foregoing, from which it is separated by a quartz grit layer ; it is 
a grey sandstone, including a calcareous cement; it contains a mass of broken shells, forming 
a cement mass in which are imbeded layers of ostrea and pecten ; the ostrea in this bed have 
not the size of the mollusc of the first bed. The pectens are large, rarely perfect, and when 
so, in such a soft condition that it was found difficult to preserve them. The pecten, (hinnites 
crassa, vide Conrad’s report,) as a fossil, more abundant than the oyster. This bed averages 
from 70 to 85 feet in thickness. 
Third bed varies from 60 to 90 feet thick ; is made up almost completely of white calcareous 
cement, broken shell, and quartz pebble. The fossils lie in two layers, separated by a bed of sand 
rock. The lower layer contained ostrea and pecten (hinnites) about 60 inches thick. in the 
upper, ostrea and asterodapsis. The latter (echinoderm) is the characteristic of this bed; it 
was not found in the lower beds ; the individuals vary in size from to inch across ; they 
are in every respect similar to the Estrella fossils ; pecten discus of a small size was found 
in this upper bed. 
Fourth bed. A soft brown sandstone, which splits readily into thin slabs, perforated with 
circular holes, three-fourths inch in diameter, bored obliquely, showing the action of boring 
molluscs upon it; thickness from three to six feet. 
Accompanying the echinoderms. was a mass of broken fragments of their own species ; this 
Comminution took place while the bed was yet soft and inhabited, as few of the specimens are 
broken in place, though so brittle that it is difficult to remove them ; they lie crowded together 
and conformable to the plane of deposition, as do also the ostrea and pecten. The ostrea lie in 
regular layers with their flat shell uppermost, apparently undisturbed except by the general 
elevation. 
Mr. Conrad has described the pecten as a hinnites, and given the characters of the fossils 
in his report. 
These four beds were never found together in the same immediate locality, but usually 
within a longitudinal range of five miles. The first bed was rarely upheaved, and constituted 
the level ground of the valley ; while beds two and three were usually found cropping out of 
the low hills on the east side of the valley; the continuity was, however, satisfactorily traced 
in several instances. Some of the beds, as that containing the asterodapsis ( laganum ,) was 
