44 FOSSILIFEKOUS 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 ; but 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 

 l^art 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 j^reserve 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 1^ 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 (Jaganum,) was 



