LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

108 LOWSB CEETACEOUB DEPOSITS IN CAHFOSNlA AND OREGON
In its association with the above forme it recalls a species of Aucella found in the
Barr zone of the Cottonwood district, California, also in Aptian strata.
OSTBEIDAB Lamarck
Oiirfo Linnaeus
Oilrta indigem Anderson, n„ ap.
{Pkta 1, Inn 1, »
Shell largo, thick, and maasive; upper (right) valve irregularly semicircular, or
ovate in outline, beak aubtermmal, posterior end rounded; valve moderately thick,
concave, or excavated above; lower (left) valve high, thick, and aogulhted, massive;
beak curving forward and toward the side; left valve strongly arched, with angular
ridge extending from tbe beak to the posterior margin; elope steep toward the back,
gentler toward the front; neither valve corrugated, or much roughened, marked only
by the almost smooth edges of the lamellae, not showing transverse folds.
This shell bears much resemblance to Ourea eoulom Dafrnnee, as figured by
Weaver (1931, p. 229, pi. 19, figa, 90,01), from the lower Neocomian of western Argentina,
of which it is at leaat an analogue. Stanton (1896, pi, 2, fig. 1) has figured a small
upper valve of a shell found near Stephenson's on the Cold fork of Cottonwood
Creek, which may be the young of this species, since both are found in the Paskenta
group, although not in the aame bornon.
The holotype (Calif. Acad. Sci. type Coll.) measures: length, 145 mm.; greatest
width, 96 mm,; thickness ai both valves, 70 mm. This example was found by E. J.
Broad at Locality 113 (Calif. Acad. Set.), 4 miles southwest of Ono, Shasta County.
Its horizon is in tho upper part of the Paskenta group in the Cottonwood district.
Another example of the same species was found by the writer in the NW } Sec. 7,
T. 28 N., E, 7 W. These examples were found on nearly the same horizon, and both
were found associated with Acroleulhit ihantenri*, beneath the lowest beds assignable
to the Horsetown group.
TBIQONIIDAH Lamarck
Trigonia Bruguj&re
Trigonia kayana Anderson, n. sp.
(F1*U> 7, Brsr® I)
Trigonia aequieottala DILTJSB and KAY, TJ. 3. Geol. Surv., Geol. Atlas, Riddle Folio,
1924, p. 3, fig. 3; 1 'Knoxville formation," Riddle Quadrangle, Oregon.
The shell of this apeciea is small, or of only moderate sine, as judged by the betterknown
forma with which the figure appears in the folio. The species is quite unlike
T. aeqvicostala Gabb which occurs ia the lower beds of the Chico series, and it requires
a distinctive name. It seems to be among the oldest forma of Trtgonia yet
found in the West Coast Cretaceous. A similar form haa been found en Eagle Creek,
near Ono, Shasta County, in tbe lowest beds of the Hisraatown group. At present
the horizon of the Riddle example IB subject to question, since it ia included in a
list of "Knoxville" forms, which includes Aucella piochi Gabb, A, "eraasicotfiV
{= .-1. cranxa Pavlow), and Peden opeTculiJormit Gabb, and a Ginkgo loaf. An
these molluscan forms represent various distinct horizons they perhaps need revision,
A similar small undescribed species of Tnponia has been found in beds regarded
as being in the middle part of the Paskenta group on the North fork of Cottonwood
Creek, 2 milts southwest of Ono, Shasta County,