LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

description of species 119
This shell ia described by Stanton (1895, p. 60) aa follows:
"Shell of medium size, with thick test, subovato in outline, depressed,* beaks
broad, rather prominent, and situated considerably in advance of the middle:
dorsal border defending abruptly with a concave outline in front of the heak and
sloping more gently behind, where it ia straight or slightly convex; anterior end
rather narrowly rounded: posterior end broader and subtruncate below; ventral
margin forming a regular broad curve; surface marked by prominent but somewhat
irregular concentric lines.
Length, 60 mm.; height, 50 mm.; convcxity of ample valve, about 16 mm."
The genua Arclica is not often found in the West Coast Cretaceous, and its occurrence
in the lowermost beds of the California Cretaceous is therefore noteworthy.
This species is included by Stanton (1395, p. 17) among the number found neor
Stephenson's, which is here shown to belong in the lowest beds of the Paskenta
group.
SOLENIDAS Loach
&clecur(u« de Blainville
Solecurtus ? dufr'us Stanton
SoJfcurtua ? dubiua STANTON, TJ. S. Geol. Surv., Bull. 133,1895, p. 61, pi. 10, figs. 4, S;
Cold fork of Cottonwood Creek, Tehama County.
Although this form is placed under Solecurtm by Stanton, he did not feel sure
of its position. This genus has not been otherwise recorded from the Lower Cretaceous
of.California, and its occurrence needs confirmation. The species ia included
in a list of 18 forms specifically named from its type locality (Stanton, 1895,
p, 14), some of which clearly indicate that the locality should be included in the
Paskenta group. A visit to this locality confirms its position and age as being near
the base of this group, but no further data were obtained.
ABTABTIDAE d'Orbigny, emend. Dall
Representatives of record are not abundant in the Lower Cretaceous of the West
Coast. The discovery of a few apscies by Stanton in the lower part of the Shasta
aeries is the earliest record oI their appearance in California. They are found only
is scattered localities in Tehama, Colusa, and Lake counties, and in every case in the
Paskenta group, associated with other diagnostic species of the Bame.
Agtarte Sowerby
Aalarle corrugala Stanton
Antarte corrugata STANTON, U. S. Geol. Surv., Bull. 133, 1365, p. 56, pi. 6, fig. 16}
Shelton ranch, 5 miles north of Paskenta, Tehama County; "upper part, of the
Knoxvilla beds."
This species is described as "very small, subtriangular, moderately convex;
beaks prominent, acute; cardinal margin sloping rapidly both in front and behind;
ventral margin convex, most prominent behind the middle; surface marked by a
few very prominent, distant concentric ridges and by fine lines of growth; ventral
margin crenulated within. Length of largest specimen seen, 5 mm.; height, 4 mm.;
convexity of single valve, about 1 mm."
This species is included in a list (Stanton, 1305, p. IS) of specifically named forms,
including auch typical Paskenta species as Avsella erasticoltit, "Eoplites" angulalus,
"Oleaatephanus" muiabilu Stanton, and others. The horizon is in the Valaoginian,
upper part of the Paskenta group, although Spath (1624, opp. p. 80) places the lastnamed
species in the Infra-Valanginian.