LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

158 lower chetaceous deposits ijf california and oregon
Neocraapeditea wilevxi Anderson,, n„ ep.
(FLutd 18, 8(wg 1- pLita 17, fimro I)
Shell large, diacoidal, moderately inflated, rounded on the periphery; umbilicus
moderately broad, walls steep, abruptly rounded on the border to meet the flattened
sides; section of whorl elliptical, sides sloping gently to the rounded periphery;
sides rather weakly eestato, marked by a few slightly sinuous, inconspicuous transverse
grooves and costae; costae arising on tbe umbilical walls as low ribs and hollows,
inclining at first backward, then forward on the umbilical border, where they
tend to divide; both costae and grooves rising on the sides with a alight forward
inclination, cross the ventral zone without interruption; suture line partly shown
in the figure. The holotype (Calif, Acad. Sci. type Coll.) consists of a little less than
half a whorl, septate throughout, which permits the following measurements (in
part): greatest diameter (est.), 138 mm.; width of umbilicus (est.), 45 mm,; height,
of whorl, £3 mm.; thickness of whorl, 43 mm.; umbilical ratio, 0.32$: 1, This specimen
was found by Mr. M. A. Wilcox on the eastern, portion of his ranch, 5 miles north
of Paskenta, Tehama County. According to his statement, and as shown by the
lithological character of the matrix, its horizon is not far from that of the preceding
species, although it may he somewhat higher. It is believed to represent the lower
part of the Hometown group in the district between McCarthy Creek and Elder
Creek, Tehama County.
Dtchotermitea Ichamaen&is Anderson, n, sp.
IS. Start 3; pints 39, Bpuv «J
Shell of moderate size, moderately robust, narrowly umbilicatc, finely coatate
in young stages, almost smooth in mature stages; shell bearing a few irregularly
spaced constrictions; umbilicus somewhat funnel shaped, deep, with steeply sloping
walla, rounded on the border; periphery rounded; umbilical ribs about 40, rather
weak, branching into three or four minor riblots near the middle of the side, inclined
strongly forward; in older stages of growth all the ribs become almost obsolete,
particularly on the inner port of the whorl. The holotype (Calif. Acad, Sci. type
Coll.) affords the following measurements: greatest diameter, 73 mm.; width of
umbilicus, 17 mm,; height of whorl, 33 mm.; thickness of whorl, 2S mm,; umbilical
ratio, 0.233:1.
This species occurs in "Zone M»" of the Paakenta group on the Wilcox ranch, 5
miles north of Paskenta, Tehama County, Its horizon ia at or near the middle of the
Paskenta group and also near the middle of the Valanginian stage. The holotype
woe donated to tho California Academy of Sciences by Mr. R, B. Fripp of Corning, to
whom the Academy is indebted for other characteristic species from thia district.
XKdrteomttu gregencni Anderson, n, sp.
{Plate IS, fisuns S,4)
Shell of medium sizo, discaidol, moderately compressed, narrowly mntailicate,
rather coarsely eostate, periphery narrowly rounded; interior of umbilicus ribbed,
walls abrupt, nearly vertical, croaned by the interior ribs which are inclined backward;
after passing the umbilical border these are inclined forward on the lower half
of the side; major ribs branching near the middle of the side into two in young shells
and into three in mature shells; the minor costae are inclined forward on approaching
tbe periphery which they cross without interruption; in mature shells the major ribs
often become pinched into narrow ridges. Normally, there are three branches from
the major ribe. The holotype of this apeciee (Calif. Acad. Sci, type Coll.) was