LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
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120 loweb cbetaceodb <strong>DEPOSITS</strong> in california. and oregon<br />
Aslarlt californica Stanton<br />
Antarte California! STAXTON, U. S. Geol. Surv,, Bull, 133, 18S5, p. 67, pi. fl, figs. 19-<br />
21; "upper part of the Knoxville beds," near Stephenson's, Cola fork of Cottonwood<br />
Creek, Tehama County.<br />
Stanton's excellent detailed description of this species needs no special comment<br />
except as to its assignment to the Knoxville aeries. Tbe species is included in a<br />
list of 18 molluscan Species (Stanton, 1895, p. 14), which also contains Aucella crassifollit,<br />
Lima muUilintata, and Acrotiuthit impretsa {Gabb), all of which are characteristic<br />
of the lower part of the Paskenta group of the ShaBta series, it appears,<br />
however, that this species has a greater vertical range than others of this list, since<br />
it has been found in the lower part of the Horsetown group—the Ono zone—at<br />
Locality 1353 {Calif. Acad. Sci.) near the bridge at Ono, Shasta County, By its<br />
position as well aa by its fauna, the type locality of this species must be regarded as<br />
near tbe base o£ the Paskenta group.<br />
A starts traptioidalvi Stanton<br />
AttarU irapezoidalit STANTON, U. 3. Geol. Surv., Bull. 133,1895, p. 57, pi. 8, figs, 17,<br />
18; 3 miles south of Lowry's, Tehama County.<br />
This species baa been adequately described and figured by Stanton, who has also<br />
stated that it has been found at other localities. The locality given for tbe holotype<br />
aa 8 miles south of Lowry's places it well within the limits of the Paskenta group,<br />
and its occurrence near Reiff, Lake County, associated with Pecten corpplczicosta,<br />
Aualla cratsicoUit, and ITurto vtfourmjts supports this conclusion. Like the two<br />
preceding species this one must also be regarded as representing a low position within<br />
the Paskenta group, and a Valanginian horizon.<br />
Opis Defraneo<br />
Opii californica Stanton<br />
OpxD caUforniea STANTON, U. S, Geol. Surv., Bull, 133, 1895, p. 58, pi. 7, figs. 1-7;<br />
near Stephenson's, Cold fork of Cottonwood Creek, Tehama County.<br />
This is the first reoord of the occurrence of Opi'j in the Lower Cretaceous of California,<br />
although others have since been found. Tbe description given by Stanton<br />
is in part aa follows: ' -<br />
"Shell of medium size, with the outline triangular when viewed from the side,<br />
and cordate in Profile; beaks submediau, narrow, prominent, incurved, and approximate;<br />
surface divided by a sharply angular umbonal ridge into two distinct areas,<br />
of which the posterior one is nearly plane and so abruptly deflected that it is scarcely<br />
viatblft from the side view, although it embraces about one-third of the total surface<br />
of the valve; front and ventral margins regularly curved from lunule to the end ot the<br />
umbonal ridge, where it forms an angle of about SO* with the truncated and deflected<br />
posterior end; surface marked by fine lines of growth and more distant, irregular,<br />
concentric furrows; lunule cordate, Urge and very deep, with its border narrowly<br />
rounded;.. . The hinge shows the characteristic structure of the genua, with a<br />
single very large striated triangular tooth in the right valve and two smaller ones<br />
in the left, of which the anterior is fused with the edge of the shell, - '<br />
The rarity of this genua in the Lower Cretaceous of California ia one of its most<br />
striking aspects. Its stratigraphies! position is in the lower part of the Paskenta<br />
group. It is listed by Stanton (1805, p, 14) with 18 apecifioally named forms, including<br />
A ucella crasaicollh and Belemnite* imprenut.