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