LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

description of species 153
this ratio increases; the sides slope from below the median line to the periphery, the
section of the whorl becoming subovate; the costal ridges form at ahout 40 mm.
diameter, and are at first rounded, separated by interspaces of about the same width;
at a diameter of 100 mm. these ridges become relatively narrow and cross the ventral
zone; the suture line is known only from Gabb's figure (ISflB, pi. 22, fig. 14b), The
holotype has the following dimensions: greatest diameter, 108 mm.; width of umbilicus,
40.6 mm.; height of whorl, 45 mm.; width of whorl, 36 mm.; umbilical ratio,
0,37&:1.
Lytoeeroa (&MsmaJe/Ja) gaineai Anderson, n, sp,
(Pitta 3D, fi|v« 3, 4, 5)
Lytoceras rel. dttvaJtanum (d'Orbigny) ANDERSON {in part), Calif. Acad. Sci., Pr.,
3d ser., vol. 2, 1902, p. 81, pi 6 figs, 140-143; upper part of Horsetown group,
Hulen Creek and Horsetown, Shasta County.
Shell small, discoidal, moderately inflated, "gradurabilieate," section of whorl
quadrate, higher than broad; surface marked by regularly spaced periodic constrictions,
about 18 to the whorl, inclined forward; between these the surface is marked
by numerous fine growth lines; both constrictions and growth lines becoming weaker,
or quite disappearing upon the abdominal surface; sides and ventral zone somewhat
flattened in older stages. In this species the umbilical ratio is smaller than in
LyCocerae duvalianttm (d'Orbigny), which belongs to a distinct subgenus.
Tbe holotype of this species (Calif. Acad. Sci. type Coll.) has the following dimensions:
greatest diameter, 58 nun.; width of umbilicus, 16.5 mm.; height of whorl,
24 mm.; width of whorl, 22 mm.; umbilical ratio, 0.384:1.
Twelve or more good examples were obtained at Locality 1656 (Calif. Acad. Sci.),
in the Neptune zone, associated with Ptttosia koffmatmi (Gabb) and other middle
Albian forms. It has also been collected at the old mining camp of Horsetown,
Shasta County, and nt Texas Springs, 3 miles to the east.
STEPILANQCEJUTUMB Neumayr
In the broader family Stepbaaoceratidae Neumayr, of the Mesosoie, later authors
have rccogni-xcd various subfamilies, among which Morphoceratinac Hyatt has found
acceptance among many. In such relationship Pavlow and Lamplugh (1661, p. 470)
groupedQlcottephanueNeumayr, Polyptychita, Simbirekiles, Astieria and Virgatilee.
Since then Spath (1624, p. 87) has proposed as family groups Simbirskitidoc and
Polyptychitidae, the latter of which Seems to cover satisfactorily many western
forms, including Polyptychitea, Simbirakitts Pavlow, and £ui)