LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

128 lower chetaceous deposits ijf california and oregon
Placer County, California; the shell is discoidal with smooth rounded whorls,, almost
circular in section, resembling the Carboniferous Cratridorta Brown.
Stewart (1927, p. 314) has commented but little upon Gabb's species and its relationship,
but concludes that it is not a Diicdhelix, Stoliczka (1306, p. 252) bad long
before placed the species in the genus Cyclogyra Wood, a group sometimes thought
to have been founded upon forms of Foraminifera.
Dall (1892, p. 331) has discussed Diteohelix at length and has proposed a new section,
Discosolit, for the American forms. The genotype, D. telijer Dall (1BG2, pi.
19, fig. 1) is a heavily nodose shell, not equally biconvex above and below. If the
other American forms, D. rotUlla Lea (Eocene), D. ncbilit Verrill, and 1>. tamillifcra
Dall (recent), are sufficiently close to be Included in Dtiteohtlix, then tbe species here
described would much better be retained with typical Diteohclix.
Wade (1923, p, 176) has described two new species from the Upper Cretaceous of
Tennessee under the names Pseudomnlaxia ripltyarta and P. amplificaia. In both
forms the whorls are slightly asymmetric in section, and tbe spiral is not equally
depressed above and below. It thus appears that the diagnosis of the genera included
in Euompbalidae offers many difficulties. The desire on the part of some
students to recognize geologic and geographic groups of species has produced a multiplicity
of names, not all founded upon sound conchological criteria. Ccasraann's
revision has not yet met with general acceptance.
£>i'«coAcJir planigi/roidei Hanna, n. sp.
(Plate 37. figoraa S, 3 a)
"Shell diseoidal, equally concave above and below, consisting of about five whorls,
square in cross section; whorls with sharp carinae at each angle, and with the surface
between the upper two and the lower two slightly concave; last half of last whorl
widely departing from the coil, in the holotype, and tending to do BO in other examples.
Greatest diameter, 8.6 mm.; smallest diameter, 5.1 mm.; altitude of bodywhorl,
about 1 mm."
Tbe holotype (Calif. Acad. Sci. type Coll.) was found on the North fork of Cottonwood
Creek, Shasta County, about a mile above the diversion dam and a mile or
more below the big bend of the creek. The holotype and other specimens are represented
by external molds of the shells, showing no distortion, but from which it is
not possible to determine the direction of the growth lines.
The species is abundant in the upper part of the Paskenta group of the Shasta
series about 400 feet above the local base of the group, and about GOO feet beneath
the Hamlin-Broad cone of Locality 113 (Calif. Acad. Sci.), containing Thurmannia
jupiler, nov., Lytoceras aulaeum nov., and Acroleuihis kernentit nov. The examples
obtained were associated with various fossil Mollusca, including a small species
of Triffonia, tfemodon cf. texlrina (Stanton), Peeten cali/trmieu* Gabb, and Turritella
sp.
The species has also been found in strata about 300 feet above the Hamlln-Broad
zone, associated with Plicatula variata, Phylloctras oceidenialia nov,, and jVeocratpcdiUs.
The horizon of the type locality is dearly within the Valanginian of European
chronology. The discovery of this interesting form in the lowest group of the
California Cretaceous warrants the preceding notes on its generic and family relationship
by Dr. Hanna.
TURBINIDAB Adams
Among the littoral mollufirao species found in the lower beds of the Shasta series
in the Great Valley of California there are many members of this family. None