LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

178 lower chetaceous deposits ijf california and oregon
on tho North Fork of Cottonwood Creek, milea above tbe mouth of Hulen Creek,
in the same *one, associated with AcnnifiopJife* sp, and furnus pienus Gabb.
In this specimen the major ribs occur in pairs, and on the latter half of the body
whorl there are about eight such pairs, some of which unite in a broad bulbous
tubercule on the umbilical border, others unite in a similar tubercule a little below
the middle of the aide; secondary riba occur between these pairs arising on the lower
part of the whorl above the umbilical border, not tuberculate except on the ventrolateral
zone; in younger whorls some of the major ribs bear prominent bulboso
tubercules upon the border of the ventral zone. In form and general dimensions
this apecies ia not unlike Chdoniceras bradhyi and occurs in the same zone.
Chthnicera* irrtgulare Anderson, n. sp.
(Flats fifurtn 2-41
Shell of medium size, discoidal, little compressed, with moderately broad umbilicus;
few ribs, nearly all of one order, uniformly broad, separated by interspaces a
little broader than the ribs; in younger stages the ribs are furnished with three
rowB of low, spinoae tubercules, which are lost at a diameter of 50 mm., becoming
first rounded, and then obscure except on the ventral borders where they become
more strongly developed; riba and interspaces crossing the periphery; riba much
depressed in the ventral zone, forming a broad saddle between tbe elevated tubercules
on the ventral borders; tubercules elongated parallel to the siphonal plane, prominent
only in adult stages, becoming lost in older stages, in which the ribs cross the
ventral area aB prominent ridgea without tubercules. The holotype (Calif. Acad.
Sci. type Coll.) haB the following dimensions: greatest diameter, 110 mm.; width
of umbilicus, 35 mm.; height of whorl, 35 mm.; thickness of whorl, 33 mm.; umbilical
ratio, 0.318:1.
In form and ornamentation this species recalls "Aeavthoeamu" ean/usum Gueranger,
from the Cenomanian beds near Hanover, Germany, although near relationship
is not claimed. In general features the form also bears some resemblance to Ammonites
im'cftelmianuj d'Orbigny, referred to by Gabb (1869a, p. 130) in his description
of Chetoniccr&e ttoliczkanum. The holotype of the present apeciea was found
about 400 feet beneath the Buenaventura zone on the west branch of Hulen Creek, li
miles above its entrance into Cottonwood Creek. The shell of this unusual form
possesses characters of Ckelmieereu, but baa no spines in its youngest and oldest
stages, whereas in its intermediate stages it developa a succession of changing types
of spines. Its horizon is believed to be near the houndary of Aptian and Albian
Stages, in the upper part of the Horsetown group. Only a single specimen has yet
been found referable to this species.
Chtlonicerae reesidei Anderson, n. sp.
(Plan 47, flfum 1)
Shell moderate in size, discoidal, little compresscd, broadly umbilicate; section
of whorl subelliptical, a little inflated, rounded on tbe sides and on the umbilical
border, flattened or slightly concave on the periphery in young adult stages of
growth; sides costate, having primary and secondary ribs; primary ribs bearing
three narrow, little prominent tubercules, seen mostly on younger whorla; ribs
becoming smoother and narrowly ridge-like at maturi ty, separated by wide interspaces;
secondary ribs arise on the umbilical border as fine intermediary costae,
becoming stronger near the ventral border, without tubercules; all riba cross the
ventral area, slightly tuberculate on its borders, but sag s little near the siphonal
line. The holotype (Calif. Acad. Sci. type Coll.) has the following dimensions: