LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

CRETACEOUS SEDIMENTARY DIVISIONS 47
sandy, and the upper part composed of shales. Although not many
molluse.Rn species have been found here which characterize the Paskenta
group in its type district, several forms of equally diagnostic value have
been obtained, showing that the lower beds in this area come within the
limits of the Valanginian stage, and, therefore, within the limits of the
Paskenta group.
Thus far no species of AuceUa, Berriasella, or BochianUes has been found
in this group north of the axial parts of the delta, and this fact is noteworthy
as showing the contrast in the faunas of the two areas. The species
common to the two areas include Lytoceras saturnaU, Aeroteuthis skastensia,
Aeroteuthis onoensis, Inoceramua ovalus, and Crioceras latum Gabb. In
addition to these a few genera may be mentioned, which, although not
specifically identical with those south of the delta, still have diagnostic
value. These include Thurmannia, Neocomite&f Subastieria, and olcostepbanids.
In both districts Lytoceras aatumale ranges throughout most of
the group. In the Cottonwood district the upper shales of the Paskenta
group include the Ham]in-Broad zone represented at Locality 113 (Calif.
Acad. Sci.), 4 miles southwest of Ono, from which have been obtained:
Polyptychic Iccontei nov. Srm&iraJh'/eir broadi nov,
Polyptyehiiea he&verius nov. LyUtteran safurnate nov.
AspmnceroM hamlini^ nov. L. auranum nov.
Acrotcuihxa thastensit nov. Qtlrea indigena nov.
In the same zone, not far distant, were found Thurmannia jupiler nov.,
Aeroteuthis anoensis nov., and Crioceras latum, Gabb.
The Hamlin-Broad zone lies about 450 feet below the lowest bed of
conglomerate at the base of the Horsetown group. At Locality 113
(Calif. Acad. Sci.) it is more than 1000 feet above the base of the section.
Farther west the zone rises above the basal contact, due to the emergence
of older beds beneath it. From the lowest bed exposed on Duncan Creek,
west of Ono, were obtained Spiticeras duncaneme nov., Ncocomiies rusaelli
nov., Crioceras latum Gabb, and Hoplocriocer as sp.
The stratigraphical relation of the Hanxlm-Broad zone to the basal beds
of the Horsetown group shows its position in the chronological column
to be below the Hauterivian, and therefore within the Valanginian. The
occurrence in it of two species of Polyptychic*, one of which is near P.
polypiychus Keyserling, a species of Simbirskitea near S. dechent Pavlow,
a species of Thurmarmia, of the group of T. boisxieri (Pictet), indicates a
low position in the Valanginian sequence. When the zone is followed
eastward it passes into the almost barren sandstones and conglomerates
at the base of the section north of Ono, In the opposite direction it
rises to 1200 feet above the base within a mile of Locality 113 (Calif.
Acad. Sci,), and a few miles farther west it is nearly 3000 feet above the
basal bed of the group. Near tbe bridge on the Menzell ranch three