LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

CRETACEOUS SEDIMENTARY DIVISIONS 67
Alderson zone. Some of these were collected by G. W, McFarland, &
part of whose collection was purchased by the California Academy of
Sciences,
Hvlcn Beds.—The boundary between tbe Cottonwood beds and the
lowest of the Hulen beds is perhaps one of paleontologies! distinction
only at present, although there are certain lithological changes found in
the Hulen Creek, section, in which the upper part of the Horsetown group
is most fossiferous. The area in which these beds are best known lies
north of the North fork of the Cottonwood Creek and is traversed by the
eastern branches of Hulen Creek, whence the name is taken. Here the
Hulen beds are overlaid by the lowest beds of the Chico series. A little
farther east both are covered by the Tehama formation, and the Hulen
beds do not appear again south of Clear Creek with the same faunal
development, although they have been found south of the delta area and
reappear at intervals south of Elder Creek, and in the Diablo Range a few
of their characteristic fossils have been found.
In their type area the lower part of the Hulen beds consists of dark
argillaceous shales, with only occasional layers of sandstone and sandy
shales and zones of calcareous concretions in which there are many fossils.
These concretions vary in size from 2 inches to 2 feet in diameter, many
of them being melon-shaped. Many of them contain ammonites or other
molluscan fossils in an excellent state of preservation; others contain only
fossil wood, but moat of them are barren. Among the plant remains a
few fossil branches, leaves, and nuts of coniferous trees have been found.
The lowest fossil-bearing zone of the Hulen beds, here called the Buenaventura
zone, occurs about 300 feet above the Reeside zone of the Cottonwood
beds. It has been identified as far south as Roaring River and
indirectly on Dry Creek, south of the delta.
Among its typical invertebrate fosails are the following:
Putosia huenaovntura nor. DowiUeiceraa mvmmiUalum var.
P. reeaidti nov. Sitoite* puzasiajormii nov.
diadmta HOT. jicartfjiopiifca tpaihi nov.
Cheionicerai sp. F«»UJ coreila nov.
This zone is best exposed on the west branch of Hulen Creek, about a
mile above its mouth, where it is characterized by many large concretions.
About 400 feet above the Buenaventura zone was found the holotype
of Pvzosia diUcri (Anderson), a distinctive form between P. buenaventura
and P. svbquadTota (Anderson).
Tbe Bradley zone, about 730 feet above tbe Buenaventura, is represented
by the following list characterized by species of Cheltmiceras. It
contains;
Cheloniceras btadUyi nov. Atanlhoplilw barryana nov.
C. aioftcifcaniim (Gabb) Turnv* j>knl« Gabb
C. popvlomm nov.