LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

150 lower chetaceous deposits ijf california and oregon
gpicuoua bullae, passing outward nearly normal to this border, but dividing below
the middle tit the side into two, three, or more finer costaa, which have a strong
forward slant, crossing the periphery without interruption, although weakened in the
ventral zone. Periphery narrowly rounded. The holotype and two additional
examples were obtained by E, L, Packard at Locality 268 (Oregon State Coll.), about
a mile east of Riddle, Oregon, and are the property of the Oregon State College. The
holotype has the following dimensions; greatest diameter, 23 mm.; width of umbilicus,
3 mm.; greatest thickness, about 7 mm. Although this species has a smaller
umbilical ratio than most members of this genus thus far found, it seems to belong
to the group of Diehotomitet fraffiliv (Pavlow, not Trautchold), which according to
Spath represents a Valanginian horizon (bed D-l) at Speeton, England. This form
was found associated with Nsacomitas riddUnsis, Phyllaceraa triniten&e, and Pecten
(Syneyelimema) sp. in a hard shaly sandstone in the first ridge cast of Riddle, in
strata overlying thick beds of conglomerate, containing in their upper part Aucetla
inflate, and AuceUa lahmeni, abundant in the lower part of the Paskenta group in
California. The horizon of this species can hardly be younger than lower Hauterivian
and is believed to be upper Valanginian, corresponding to the horizon of
Dichatvmite* iehamaeneia in the McCarthy Creek district in California.
Dichotomitei nttildfuit* (Stanton)
Ohostephan-ue (Simbirskites) muiabitie STAKTOM, U, 3, Geo!. Surv., Bull. 133, 1806,
p. 77, pi. 15, figs, 1, %, 4, only; Shelton's ranch, 5 miles north of Paskenta,
Tehama County. (Not Amm. muJa&tiis Sowerby, Lower Cretaceous of England;
not /lmm. muiabiJis d'Orbigny, Jurassic of France).
From the figures and description of this species given by Stanton (IBM, p. 77, pi.
15, figs. 1, 2, 4), one gets the impression that the shell is compressed and disk-like;
it is true that compressed forme are plentiful in the zona of the holotype. However,
among 40 examples of this genus obtained from this zone by the writer, as many as
three species were recognised, none of which were much, compressed except by rock
pressure, and they do not support the view of great variability claimed for any
apeciea among this number. Changes in the character and number of the riba can be
seen in some forms at different stages of growth, but it seems possible that Stanton's
examples included more than s. single species. One cf these examples should be
selected as the holotype, and for this we may accept the first. Stanton compares
his species to "Olcvitephanue" diswfaleatwe Lahusen, which Spath regards as Crasptdodi&tut,
Nevertheless, after a careful comparison of a large number of examples,
both forms figured by Stanton appear to belong to the group of Didwtamites fraffilia
(Pavlow), as do many others obtained from the same zone. Spath (1924, table opp.
p. 60) refers Stanton's specica to a low position in the stratigraphic column—namely,
that of Subcraipedilea atcnemphaltit (Pavlow)—and therefore to a low Valanginian
horizon, although most of the Polyptychicdae at Sp-eeton are placed higher in the
column. The horizon of the present apecies, like that of the next three species to be
discussed, is not lower than middle, and may better ho regarded as upper Valanginian,
corresponding to the horizon of the Hatnlin-Broad zone in the Cottonwood
district of Shasta County.
JSpttiecroa Ulilig 1903
Spiiictraa duneanenae Anderaon, n. sp.
(Plata 37, figurn I, :)
This apecies appeara to belong to the group of (Sptitccraa ducale (Matheron), AS
figured by Kilian (1910, pi, 2, fig, 4), found in the zone of Thtirmanitia b&iuicri