LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

description of bpbcte3 177
border, and one near the middle of tbe side; the minor riba have only the two latter
rows, and some of them show scarcely any tubercules, or only swellings,
The holotype affords the following measurements, differing somewhat from
Gabb's: greatest diameter, 00 mm.; diameter of umbilicus, 30 mm.; height of whorl,
38 mm.; width of whorl, 48 mm.; umbilical ratio, 0,333; 1.
Tbe exact horizon from which the holotype was obtained is not definitely known,
although on immature shell that seems to belong to the spcciea was found on Hulen
Creek in the Bradley zone, which also contains CAetam'ceras bradhyi and another
related spcciea. It seems prohabU that this is the zone from which Gabb's holotype
came. This sone is situated about 340 feet above the Buenaventura zone of the
Hulen beds and nearly 1700 feet below the top of the Horsetown group. Its position
on the chronologic scale of Europe is probably lower Albian. Gabb has compared it
to European species from the Gault. The species does not appear to have been found
at any other place or horizon in California. Whiteaves seems to have figured more
than one form under this name, all of which he later included under tbe name Aeanf&oeeros
apinijerum ("Nom. mut."). Kossmat, to whom a specimen of "Acanihoeeras
tjriniferum" Whiteaves waa sent, aeema to have regarded it as belonging to
DuuirtUeittraa, rather than any type here included in Chelonicerot Hyatt. None of
the forms figured by Whiteaves appear to belong to Gabb'a species.
Chtlonicwos bradleyi Anderson, n. sp.
{PUioiS, fipi»*l,
Shell Large, robust, very broad, with deep umbilicus; few whorls, bearing about 20
major riba with intervening Bmaller riba that occur in pairs on tbe large whorls;
major riba tuberculate, with three rows of rounded but elongated, although not
prominent, nodes; one pair on the ventrolateral zones, bearing transversely elongated
"bullae," an inconspicuous one on the umbilical border, and a rather prominent
one on the middle of tho side; smaller intervening costae without nodes;
umbilicus deep, walls smooth and vertical, or showing faint backward-sloping
grooves; riba crossing the periphery; periphery excavated on major riba only, rounded
between.
The holotype (Calif- Acad. Sci. type Cell.) has the following dimensions; greatest
diameter, 155 mm.; width of umbilicus, mm.; height of whorl, 58 mm.; width of
whorl, 86 mm.; umbilical ratio, 0.355:1.
Two incomplete examples of thia species were obtained at locality 150 (Calif.
Acad. Sci.) near the head of the east fork at Hulen Creek, about 340 feet above the
Buenaventura zone of the Hulen beds. Its horizon is near the lower limit of the
Albian or possibly in the highest beds of the Aptian division of the Horsetown group.
This species differs from Chtlcniteraa atoliczkanum (Gabb) in being much more
robust and broader, with less prominent ribs, and tubercules. It appears to belong
in nearly the same sane, as determined by the strike cf the beda and the strati graphic
rel ations. The zone of this species is here known as the Bradley zone. Two young
and immature examples of C. iloZicrtaMtim were obtained at Locality 165 (Calif.
Acad. Sci.) associated wi th the present species,
Chdcniceras -populorttm n. ap.
{Pl»w S3. Sturc Ji
A single large but incomplete example of a specie? oF CAefanicirtM nearly related
to C, bradhyi was found associated with it on the head of the east branch of Hulen
Creek (Locality 150, Calif. Acad. Sci.), and a similar example of the same was found