LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

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