LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

description of species 221
south at Locality 90S (Calif. Inst. Tech.), and half a mile east of the Jordan house.
The stratigraphic position of tbe species is thought to be upper Aptian (Gargasiaa).
Hemibacvlite$ nauplius Anderson, n. sp.
(Plats M. tpja 3, 3a)
Shell smaltj section elliptical, narrowing slightly toward the ventral border,
costate, with low rounded, and nearly straight costae, inclining forward and crossing
the ventral zone without interruption; ribs non-tubcrculate; dorsal zone nearly
smooth, showing only depressed costae; septa as shown in the figure. The holotype
(Calif. Acad. Sci. type Coll.) was found at Locality 1347 (Calif. Acad. Sci.) near
Mitchell Creek, in the Mitchell zone, 5 miles south of Ono, Shasta County. It has
the following dimensions; length, 100 mm,; greatest width, 30 mm,; greatest thickness,
22 mm.; shell tapering gradually and showing only a slight tendency to curve.
At its larger end there is a slight swelling and possibly the beginning of a more definite
curve, Whether this shell possessed a retroversal body-chamber is not known.
Thie species appears to belong to the group of uncoiled ammonoids represen ted by
"Toxoceraa" obliquotum d'Orbigny, the genotype of Hyatt's genus. It was found
at the top of the Mitchell zone, in a bed containing jSAailicn'cceras ponienfe nov.,
Jnoceramus ovaloidea, and other apecies thought to represent an upper Qarremian
horizon. It is the ol dest form of the genus found in the Cottonwood district. Only a
single example of the specics was found.
Hemibaeulites cyclopius Anderson, n. sp.
(Plata 5$, figure 3; plate 60, figoraa 3,3a)
Shell large, nearly straight, tapering gradually; acction broadly ovate, narrowing
in outline section toward tbe ventral border, broadest near the opposite border, a
little flattened on the dorsal zone, narrowly rounded on the ventral zone; sides
moderately costate, with oblique, rounded, unequal riba, 2 to 4 mm. in width, arranged
in groups of five or six, the central one stronger than the others; costal groups
separated by slight depressions; septa shown in the figure. Tbe holotype (Calif.
Acad. Sci, typo Coll.) has the following dimensions: total length (incomplete),
388.8 mm. (15.3 inches); maximum diameter, 75 nun.; greatest diameter at smaller
end, 38 mm.; median diameter, 67 mm. This example was found on Alderson Creek,
2 miles south of Ono, Shaata County, in a shale bed about 200 feet above the horizon
of Tropaeum pcrcoxtalum (Gabb), and 80Q tq M0 feet above the Mitchell zone with
Shaxticriacerae panienie nov. It was associated with Lyloeeraebaien (Traak), A trots tttkis
imprests (Gabb), and Phy Hoc eras onoenee Stanton. Thia example a haws no
early coil nor any recurved body-chamber, although it exhibits some evidence of
having possessed the latter, having a slight expansion in the ventro-don&l diameter
at its bucal end. Thia is the longest example of this genua that haa boon found,
although not the largest in diameter, being exceeded in this respect by ff. mfra&ffis
nov. Only a single specimen of this species has been found.
Hemibaeulites neleus Andcraon, n. sp.
(Plate S», Octroi 3.2i, 3)
Shell of medium size,, tapering very gradually, only slightly curved, section of
shaft broadly elliptical, surface costate, with low, rounded, slightly curving ribs
which cross the ventral zone without interruption, becoming faint in the dorsal zone;
septa not well preserved. The holotype (Calif- Aead. Sci. type Coll.) consists of ft
fragment of the shaft which ia costate throughout. It measures SI mm. in length;
greatest diameter, 33 mm.; greatest transverse diameter, 30 mm. It was found at