LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

DESCRIPTION OF SPECIES 115
PLBUBOWTACJOAK Zittal
PUurpmya Agassis
PUuromya papyracta Gabb
PUwomyapapyracta GABB, Paleont. Calif., vol. 2,1809, p. 178, pi. 29, fig. 68: Cottonwood
Creek, Shasta County, "Shasta Group' '—STANTON, Jour. Geo!., vol. 5,
1897, p- 597, 598; Horsetown beds—STEWART, Phila. Acad. Sci., Spcc. Publ.
no. 3, 1030, p. 303, pi. 2, fig. Si Gabb'a holotype figured, locality as given by
Gabb.
Stewart includes this species doubtfully in the genus PUuromya, but docs not
indicate any more appropriate genus for it. The shall is thin and not often preserved.
Good casts have been obtained at various places and at different horizons
north of the delta, which show a range from the lower beds of the Paskenta group
to the top of the Horsetown, Two good examples were found at Locality 1059
(Calif. Acad. Sci.) in the Neptune gone of the Hulen beds, 450 feet beneath their
top, and also at Locality 1668 (Calif. Acad. Sci.), 200 feet lower in the section.
These examples fully conform to the characters of the holotype as figured by Stewart,
but less to Gabb's figures. As suggested by Stewart, Gabb'a figures were often
"reconstructed."
At Locality 1659 (Calif. Acad. Sci.) the species is associated with Bcudnnlicttat
brewcri (Gabb) and Douviilriccrat mamtnillatvm var. Stewart gives the following
dimensions for tbe holotype: length, 45.5 mm.; height (incomplete), 20 mm,; thickness
of both valves, SO mm.
The same specieB bos been found at Locality 1665 (Calif. Acad. Sci.) on Duncan
Creek, associated with Crioeera* taium Gabb and Spiiieeriu duncartense nov.
Smaller examples that seem referable to the same species have been collected on
Eagle Creek, near Ono, and at Clements ranch oo Redding Creek, Trinity County.
PHOIJADOMTACIDAE Gray
Pkaladcrmya Sowerby
Pholadomya hultmana Anderson, n. sp.
(Plata 3, fiiurm 1, 2)
Shell of medium size, robust, triangular in outline, umbones high, anterior to
center of shell, inflated, beaks curving forward and inward, approximate; shell excavated
in front of beaks; posterior cardinal margin sloping moderately steep, anterior
slope much steeper, the two slopes forming an angle of about 00 degrees; tho
anterior margins of the valves meeting in a narrow ridge beneath the beaks; anterior
and basal borders closed; posterior end apparently open; surface of shell ornamented
with narrow beaded costae radiating from the beaks toward tbe basal margin, more
prominent on the anterior part of the shell.
The species somewhat resembles Ph-oladomya harrigani Hall and Ambrose, from
the Upper Cretaceous beds near Altamont, Alameda County, but the horizon of tbe
present species is much lower in the general section, and the form of the anterior
end of the shell is leas abrupt. The holotype of the present spccios (Calif. Acad.
Set. type Call.) was found at Locality 1063 (Calif. Acad. Sci.) on tbe west branch
of the east fork of Hulen Creek, in the Perriu zone. Its measurements are as follows:
length (incomplete), 50 mm.; height, 40 mm.; thickness of both valves, 33 mm.
It was found associated with Pinna eqtiivillana, Sonneralia rogersi Hall and Ambrose,
Clconiceras vwdtstc, and Naulilut gabbi Anderson, The horizon is probably lower
middle Albian, on the European acale.