LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

DESCRIPTION Of SPECIES 191
series, but baa been recorded from the upper part of the Horsetown group associated
with the preceding. Its occurrence in concretionary blocks in tho near basal conglomerates
of tho Chico series at the mouth of Hulen Creek lends support to the
belief that it occurs in the upper beds of the Horsetown group. The holotype is in
the Museum of Paleontology, University of California, and has been loaned for comparison
with tbe figured plesiotype from Horsetown, Shaata County. The plesiotypo
(Calif. Aond. Sei. type Coll.) has the following dimensions: greatest diameter, 57
nun.; width of umbilicus, 12 mm.; height of whorl, 28 mm.; thickness of whorl, 11
nun.; umbilicial ratio, 0.211:1.
The specics has been found abundantly at Horaetown and at Texas Springs. It
is usually without surface ornamentation, and is often smooth or polished.
Silttiti* Uhlig 1903
Sileaiiet puronci/crmis Anderson, n. sp.
{Plat* 30. firu/at 0, ID)
Two fairly well preserved examples of this genus were found in the Buenaventura
some in the lower part of the Hulen beds at Locality 1&6-A (Calif. Acad. Sci.) on
the west branch of Hulen Creek, Shasta County. They represent a single species.
The shell is small , discoidol, compressed, and broadly umbilic&te; section of whcrl
narrowly elliptical, with gently convex sides, sloping toward the periphery; sides
marked by slightly sinuous transverse grooves unequally spaced, which cross the
ventral zone with a forward sinus; between the grooves are 7 to 12 narrow costae
concentric with, them, also crossing the periphery without interruption. The holotype
(Calif. Acad. Sci. type Coll,) has the following dimensions: greatest diameter,
22 mm.; width of umbilicus, 8 mm.; height of whorl, 8 mm.; thickness of whorl,
mm.; umbilical ratio,0.331:1.
Thia species very closely resembles Silesitet deamoccraioid^ Stolley from Lago
San Martin, western Patagonia, to which it stems to be closely related. Stolley did
not definitely determine the age of ths beds containing this species but thought they
were probably upper Neocomian, citing the view of Ch. Jacob, however, that tbe
genus Stleriies is not confined to the Barramian stage but may occur in Aptian, or
even in. Albion strata in the south of France. At the type locality of our species in
the Cottonwood district, it occurs in the same beds with Douvilleicerat mammifioium
var., Pusosia bucnavcntura, and other species that range higher in the section. The
genus jSifrsftea is rare ia the Cretaceous of California, this being the only record of its
occurrence. Fragmentary specimens that may pertain to the genus Gave been found
in beds farther south that are regarded as Aptian, Whiteaves described a small form
of similar appearance to which he gave the name "Holcodisctis" laperousianus, reported
to have come from the east end of Maude Island (Whiteaves, 1879, p. 39, pi, 3,
fig. 3). According to Stanton (MacKenzie, 191&, p. 65) the formation may not bo
older than Gault,
Holtodiaeut Uhlig 1S83
Genotype, Ammonite* caillaudianve d'Orbigny
Holcodineita tehomaensis AnderBon, n. sp.
(Plats S3, figure 5)
Shell large, coiling lytoceratid, little involute, numerously costate with major
and minor ribs and about 24 periodic constrictions to a mature whorl; constrictions
bordered on both sides by elevated ridges bearing irregular elongated spurs (on the
cast), four on each aide; surface of shell bat ween major costae bearing 4 to 8 inter-