LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

208 LOWER CRETACEOUS DEPOSITS IN CALIFORNIA. AND OREGON
zona flattened J shell costate throughout, having the costae somewhat reduced
on the dorsal side of the shaft, stronger on the ventral border, especially on the
body-chamber; coatae rounded, separated by narrow, rounded interspaces; on tha
smaller coil tbe costae are narrow and the interspaces broader; costae not showing
spines or tuberculea on any part of the shell, including its earlier coils; costae often
dividing near the dorsal border and on the upper part of the side; two constrictions
visible, crossing tha aides and ventral zone near the crosier, deep and narrow. Tha
holotype (Calif. Acad. Sci. type Coll.) was found by E. J. Broad in the Hamlin-
Broad atone at Locality 113 (Calif. Acad. Sci.), 4 miles southwest of Ono, Shasta
County, and was donated by him to the California Academy of Sciences. The horizon
of discovery ia about 500 feet beneath the lowsat beds of the Horsetown group.
It waa associated with PoitrpijrcJiijM sAojfcnsis nov., Lytoeeras auiaeum nov., Aeroleu-
Ihit skasterms, and other upper Valanginian apecies. The holotype has the following
dimensions: length (incomplete), 85 mm.; maximum height of whorl, 30 mm.; maximum
thickness, 27,5 mm.; sutures known only in part, including a stout first lateral
lobe having asymmetrical, tripartite divisions, and an asymmetrical, deeply cleft
second saddle, the secondary lobe being tripartite, terminating in acuminate points-
The speeiea appears to belong to the group of "CHoeeras" dilalalum d'Orbigny,
from the Xeocomian of France.
ANCYLOCERATIDAE Hyatt, emend. Whitehouse
Hyatt included in thiB family many Lower Cretaceous trituberculate genera, not
only belonging to the type of Ancyloceraj nwtAenmianttm d'Orbigny and A. renauxioflum
d'Orbigny, but also other widely divergent forms. According to Whitehouse
(1026, p. 207-217), "Even if restricted to the trituberculate genera, the family is
certainly heterogeneous," However, with Ancyiocerat (t. a,), which is trituberculate,
he includes in the family other genera which are non-tuberculate, and which
do net coil in the manner of Aneylot&ra*. He statea that the immediate ancestor of
Ancyloceras is unknown but suggests a succession of genera which may possibly
belong in this lineage, including Australiceras, which is trituberculate in its early
stages, Ttopaettm (Sowerby) Hyatt, which ia non-tuberculate, and Aznmoaitoetrai,
which ia bituberculate. These are found in the Aptian (Bcdoulian and lower Gargaaian),
occurring in the order in which they are here named, insofar as they occur,
or are known in eastern Auatralia. In the Lower Cretaceous of California the sequence
is the same, but it seems to begin with Ancyloceras in the Barremian, and as
far aa known it closes without any known apecies of Ammoniioceras. In later Gargasian
time the smaller forma, here included In Hamxliitras (a. gen.), make their
appearance, but any relationship to Ancyloceras has yet to be determined, although
they are included in this family.
To the genera included by Whitehouse tn the family the writer has added Sfwwtoetras,
n, gen., and Hamitieeras nov., and it may later appear that some genera here
assigned to Crioceratidae would be better placed in Ancyloceratidae.
Ancyloceras d'Orbigny
Genotype, Ancyloceras matheronianum d'Orbigny
In the Lower Cretaceous of California there are many ammonoid forms referable
to Ancyloceras (a, ».), moat of them occurring in upper Barremian and lower Aptian
strata. Xo ancestral forms are known in earlier beds of the Shasta series, or in fact
in any West Coast Mesozoio deposits, and, although apecies of Lytoeeras and Crioceras
are well known in the Paakenta group (Valanginian), the ancestry of Ancyloccrat
is not at all clear. The genua appears rather suddenly in the stratigraphic section,
seems to have li ved only a short life in the Great Valley embayments, and to have
disappeared as suddenly aa it eamo. It is not evident that its several species left any