LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON
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118 loweb cbetaceodb deposits in california. and oregon<br />
speciea found in the Ripley formation of the Atlantic states, stating that the genus<br />
may also include the Lower Cretaceous "Periploma" robinaldina, P. neocamieiutit,<br />
and P. timplex of d'Qrbigny. Finding later that Leptomya was preoccupied, Conrad<br />
substituted the name PertpJtwya for the group. Stewart expresses the belief that<br />
the genotype, P. applicala (Conrad), is congeneric with certain species of Thracia.<br />
This surmise may be well founded, yet for the present it seems best to retain Conrad's<br />
inclusion of the genus in Anatinidae Dall- At least two species of this genua<br />
have been found in the Lower Cretaceous of California, both apparently belonging<br />
to tbe group of Pen'ptem&fl robinaldina (d'Grbigny).<br />
Periplomya tnnitensis Anderson, n. sp.<br />
(PUte t, flauro 7}<br />
Shell of medium size, elongate, a little inflated, Oval or elliptical in outline; umbones<br />
aubantcrior, about one-fourth the length of the shell from its forward end;<br />
beaks incurved, approximate; shall excavated before and behind the beaks; posterior<br />
cardinal margin straight, nearly parallel to the base, rounded behind to the narrowly<br />
rounded end; anterior portion short, abruptly rounded to the basal border; basal<br />
border straight in its forward two-thirds, curving upward behind; surface marked<br />
by weak concentric growth lines; a subangular ridge extending from the umbones<br />
downward to the base; valves but little open behind.<br />
The holotype (Calif, Acad. Sci. type Coll.) was found by N. E. A. Hinds near<br />
Clements ranch on Redding Creek, eastern Trinity County, associated with Phylloxera*<br />
elemental, nov. and Pholadomya clemenlina, nov. It has the following measurements:<br />
length, 62 nun.; height, 27 mm.; thickness of both valves, 20 mm.<br />
Periplomya reddingenti* Anderson, n. sp,<br />
{Plato J, Stum 8)<br />
Shell of medium size, elongate, inflated in tbe uunbonal region, subellipticaL in<br />
outline; umbones situated mar the anterior end, rather prominent and broad; beaks<br />
incurved, approximate; shell excavated beneath tho beaks; cardinal margin nearly<br />
straight, curving gradually down behind to the rounded posterior end; anterior<br />
portion shorter, more abruptly rounded, forming a short subangular bend to meet<br />
the anterior basal border; basal border rounded behind, but with a slightly concave<br />
outline beneath the umbonca. This species is larger and mors inflated about the.<br />
umbones than the preceding form, and possesses a more open, broader cardinal area.<br />
The valves are also somewhat more open behind than tbe preceding speciea.<br />
The holotype (Calif, Acad. Sci. type Coll.) was found by G. D. Hsnna at Locality<br />
1691 (Calif. Acad, Sci.) half a mile northeast of the Clements ranch house on Redding<br />
Creek, eastern Trinity County. It has the following measurements: length,<br />
mm.; height, 32 mm.; thickness of both valves, 23 mm.<br />
The holotype and other examples of tbe species were found associated with<br />
Panctpe sp., Plenromya papyraeea Gabb, Periplomya frtnifeiwfs, nov,, Photadomya<br />
altumbojwta, nov., and Venus coHtitae, nov. The horizon is believed to be tbat of the<br />
upper part of the Paskenta gTOup.<br />
PLBDnQpnoniDAB Dall<br />
Areiiea Schumacher<br />
Arciica occidentalis (Whiteaves)<br />
Cyprinn occidentalis WHITEAVES, Mes. Foss,, vol, 1, U5S4, p. 237, text figure 10—<br />
STANTON, tJ. 8. Geol, Surv., Bull. 1313,18fl5, p, 60, pi. 12, fig. 2; near Stephenson's,<br />
Cold fork of Cottonwood Creek, Tehama County.