LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
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DESCRIPTION OF SPECIES 109<br />
PxcnmvA* Lamarck<br />
Pesttn Mailer<br />
Pecten umplexicatta Gabb<br />
P«ef«n eempJ*:nVo»K» GABB, Paleont. Calif., vol. 2, 1809, p. 199, pi. 33, fias. 97, &7aj<br />
"Shasta Group," Morgan Valley, Lake County—STANTON, U. 3. Geol, Surv.,<br />
Bull. 133, 1896, p. 37, pi. 2, figs. 7-9; Wilbur Spring?, Colusa County—<strong>AND</strong>ER-<br />
SON (in LAWSON), U. 3. Geol. Surv., San Francisco Folio, 1014, p. 8; Berkeley<br />
Hills, Contra Costa County,<br />
This shell is of moderate size, thin, equivalve, neatly equilateral; aidca and base<br />
forming a regular curve; shell slightly elongated; surface marked by about 12 to<br />
14 radiating ribs, with aoraetimca on equal number of intermediary ribs. The length<br />
of tbe holotype, about 57 mm.; width, 50 mm.<br />
Gabb states that it is common in the limestone of Morgan Valley, Lake County,<br />
Stanton found it in the limestone south of Wilbur Springs, Colusa County, and it<br />
occurs in tbe Berkeley Hills, associated with Afrciiua h'ratas Gabb, and with other<br />
well-known species characteristic of the Paskenta group.<br />
Pecten californicut Gabb<br />
Pecten Mlifomicut GABB, Paleont, Calif., vol. 1, 1884, p, 201, pi. 31, fig. 270; Cottonwood<br />
Creek, Shasta County, California—STANTON, U, S, Geol. Surv., Bull. 133,<br />
188£, p. 30, pi. 2, fig. 10; Cold fork of Cottonwood Creek, Tehama County.<br />
This small species of Pecten occurs in both, the Pfwkenta and Hor&ctown groups,<br />
and both north and south of the delta area on the west border of the Sacramento<br />
Valley. Gabb seems to have confused this species with another occurring in the<br />
Chico scries, giving the horizon of its occurrence as "Chico or Shasta group," Cottonwood<br />
Creek. It has not been seen by tfca writer in the Cbieo series; Stanton<br />
reported it from "near Stephenson's on the Cold fork of Cottonwood Creek, in beds<br />
near the base of the Paskenta group, of the Shasta series, where it occurs with many<br />
other species listed by bun (Stanton, 1395, p. 14). The same species has been found<br />
abundantly in the lower part ol the Hor&ctown group on McCarthy Creek, a quarter<br />
of a mile west af the Lowry Road.<br />
Syncycl&nema Meek, 1&64<br />
Syrtcydomma operculiformii (Gabb)<br />
Pttlen Qpervutifttrmit GABB, Paleont. Calif., vol, 1, 1854, p. 201, pi. 28, fig, 188:<br />
vol. 2, 1809, p. 200, 251: Cottonwood and Hulcn-crceks, Shasta County, ana<br />
Curry's near Mount Diablo—STANTON, U. S, Geol. Surv., Bull. 133, 1895,<br />
p. 16, 18, 32, 37; regarded aa occurring in both Shasta and Chico series—<br />
STEWAJST, Phita. Acad. Nat. ScL, Spec, Publ. no. 3, 1930, p. 120; locality not<br />
given.<br />
The simple form and unomamentcd character af this shell has made its specific<br />
description difficult. It is flatty lenticular, subcircular in outline below the auricles;<br />
interior of the shell silky in texture, smooth, or polished without, but showing fine<br />
concentric lines of growth; left valve with nearly equal auric]ea, right valve less<br />
well known. The holotype ("tcctctypa" of Siewart) is in the Museum of Paleontology,<br />
University of California. It has the following dimensions ; length, 22 mm.;<br />
height, 20.5 mm.; thickness, about 3 mm. Similar forms are found in many parts<br />
of the Shasta series, and for this reason tbe range of the species ia not definitely<br />
known.