LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

144 lower chetaceous deposits ijf california and oregon
what broader interspaces; costae arising near tbe umbilical border, inclined strongly
forward at first, then rising nearly normal to tho periphery; suture lines not clearly
shown . The apecica belongs to the group represented by P. trinitense, nov. but i t is
somewhat less inflated and has finer and more numerous costae. The holotype,
which is the property of Oregon State College, measures as follows: greatest diameter,
33 mm.; greatest thickness, almost 20 mm. The umbilicus ia small, but not
closed; the ratio of height to width of whorl is near 5:4. It waa found by E. L,
Packard, at Locality 268 (Oregon St. Coll.), a mile east of Riddle, Oregon. Its horizon
is the same as that of Ncotomitea riddlentit, nov., with which it occurs.
Phylloceraa oregortetute Anderson, n. sp.
(Flat* 30, Hiurca g. 9)
Shell similar in form and sculpture to the preceding but it is relatively thinner and
has a smaller umbilicus. The holotype, which ia in the collections of the Oregon
State College, has the following dimensions: greatest diameter, 40 mm.; maximum
thickness, 10 mm.; width of umbilicus, 5 mm. It was found by E. L. Packard and
waa found with P. umpguanum at Locality 208 (Oregon State Coll.) a mile east of
Riddle, Douglas County, Oregon.
PhylloeeT/ii myrtleme Anderson, n. sp.
(Ptetft SO, figm* T)
This species is characterized by a more compressed form than any of the preceding
species. The holotype has the following dimensions: greatest diameter, 3JS mm.;
width of umbilicus, 5 mm.; maximum thickness, 10 mm.; suture line not shown;9ides
numerously costate with costae of two ranks; major costae arising at the umbilical
border; secondary costae arising near the middle of tho side; all crossing the periphery,
and all tending to branch above the middle of the side. The holotype, belonging
to the Oregon State College, was found at Locality 208 (Oreg. State Coll.), a
mile east of Riddle, Oregon, where it was found associated with P. umpquanum, Neacomitee
riddlentis, Lyticoeeras paekurdi, Dichotamitet oregonensig, and Hoplncrioceras
cf. remondi (Gabb). The horizon is thought to be upper Valanginian and to represent
the upper part of the Paskenta group, as known in California.
LTTOCERATIDAE Neumayr
Lytocera* Sueas
The genus Lyioenas, in its broader souse, is distributed str&tigraphic&lly almost
throughout the Shasta aeries in California, appearing first in a single apecica in its
lowest beds, and in increasing numbers and variety aa the column is ascended; near
the cloao of the Horsetown group it attains its greatest development, but it continues
into the lower beds of the Chico series, and appears again in ita later (Senonian) beds.
The genus existed in the Great Valley trough during the closing epoch of tbe Knoxville
period; the Tithonian stock did not continue into the Shasta series. The
earliest form of Lytocera* known ia the Shasta series seems to have entered the trough
at the beginning of its sedimentation in early Valanginian time. This waa Lylocerat
Balurnale, nov. It was followed in middle Valanginian time by Lytaeeras aulaeum
nov., and toward the end of this epoch by Lytoceiat irtaki nov.; none of these were
very nearly related.
This last form continued into the lower Horsetown group (Ono zone), where it
seems to have disappeared. At the opening of Aptian time a new assemblage of
lytoceratids appeared, consisting of types which, except for one apecieB, do not seem