LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

DESCRIPTION 07 BP ECUS 103
aiona: greatest diameter, 72 mm.; width of umbilicus, 15 mm.; height of whorl, 35
mm.; thickness of whorl, 20 mm.; umbilical ratio, 0.177:1. The costae do not continue
across the periphery as a nils, although some of the varices do so with a slight
forward curve, the number being about one to ten costae. These varices do not
appear below a diameter of 35 mm., and often 30 mm. or more, as measured on the
periphery, intervene between them. This and the following species somewhat
resemble forms of Beitdantieeraa, but they differ from those of this genus found higher
in tbe section, in having a relatively smaller umbilicus and a more convex lenticular
section.
CUonictTOi Itconiri ia found in considerable numbers in a restricted zone about
1000 feet below the top of the Horsetown group on Hulen Creek. It has not yet been
found or recorded at any other horizon in the Cottonwood district or elsewhere.
CUonieerat modfitum Anderson, n. sp.
(PUu AO, Stutw J, s, t)
In size and form this species is near the preceding, but lacks its more pronounced
ornamentation, being cither smooth or only faintly costate and showing on its sides
only traces of flesiradiate markings, scarcely to be called costae, even on the shell
itself; periphery narrow, crossed only by a number of weak varices, having a forward
sinus but scarcely ertending downward on the sides; the shell is dlscoidal, the sides
flattened; umbilicus small, with abrupt and smooth walls; Bides sloping toward tha
periphery. In young stages of growth the shell is relatively thicker and more
desnooceratid in form, but In more mature stages it becomes more flatly lenticular
and smooth, as in tbe holotype. In form the shell is intermediate between Cleoniceras
Itctmlei and some forms of Beudan(ic«ros, as seen in B. haydem (Gabb), The
holotype (Calif. Acad. Sei. type Coll.) has the following dimensions: greatest diameter,
SO mm.; width of umbilicus, 15 mm.; height of whorl, 39 mm.; thickness of whorl,
24 mm.; umbilical ratio, 0.187:1.
The suture line is partly shown in the figure and resembles that of the preceding
species. The horizon of this form is the same aa that of C, fecontei—that is, in or
immediately above the Pcrrin zone, u found in the Hulen Creek section of the Cottonwood
district.
Sonneralia Bayle, emend. Spath, emend. Whitehouse
Genotype, Ammoniie* duicmplcanua d'Orbigny
Adopting the suggestion of Spath (1325, p. 03), tbe writer here includes a group of
related apecies which occupy a stratigraphic position intermediate between middle
Aptian forms of Parakoplitea and middle Albian species of Bcudaniiceras, as found
in the Cottonwood district of California. It appears that in character also, as well
as in position, they are intermediate between these genera, although they foreshadow
the latter more clearly than they reflect the former. They are provisionally placed
in iSortniratid, as having their nearest European analogues in the group of "t/ftttflclfa"
AafttciiSis (Jacob), which, according to Spath, "might with propriety be included in
Sonneralia." Their atratigraphical position follows closely upon the principal zone
of Cltonicerat, and some of the forms such as Sonneralia ragersi Hall and Ambrose
could perhaps be placed in this genua. It is not claimed that any of tbe species here
described belongs to the group of Ammonites dutempleanita, but rather to tbat of
"tffrZtfifta" hatmemia (Jacob), aa already noted.
Per the proper assignment of the California forms the greatest practical difficulty
seems to be in the matter of finding a satiafactory distinction between Cleoniceras
and