LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

172 lowzh cbetaceous deposits in california ant> oregon
Acanlhoplite* remandt (Gabb)
(Plata J9, FLCWB t)
A mm. Retnondii GABB, Paleont. Calif., vol. 1,1864, p. 66, pt. 12, fin. 14,14a, (not Eg.
15); North fork of Cottonwood Creek, Shasta County, California.
The holotype of thia apecies is in the Museum of Paleontology, University of
California (type 102), and has been carefully studied and compared with many
individuals representing this and closely related spceiee. In. form, especially in its
lateral aspect, the holotype greatly resembles "Parahoplttet" consobrinua (d'Orbigny),
but it ia thicker in section and has a distinctly different suture line, as shown
in tbe figure. Tho holotype, Xo. 102 (Univ. Calif. Coll.), septate throughout, has
the following dimensions: greatest diameter, 137 mm.; width of umbiticus, 57 mm.;
height of whorl, 4S mm.; thickness of whorl, 37 mm.
This example possesses 38 thickened, rounded, and somewhat sinuous primary
' and secondary ribs, which occur alternately.
This holotype represents a small group of nearly related forma from the upper
part of the Horsetown group in the Cottonwood district. In thia group the whorl
section is comparatively thick, the ribs strong and often elevated, and tho umhiLicus
occupies about one-third the diameter of the whorl. The nearest foreign analogue
of this species known at present ia probably AcantkapliUs abiehi (Anthula), from the
Caucasus Mountains, as figured by Sifliow (1907, pi. 7, figs. 1-3).
The exact horizon of Acanlhopiite* remondi is not yet known, although it clearly
belongs to the middle or upper part of the Horsetown group (upper Aptian).
Hyatt referred this specie* to Acanthoceras, but upon what baais is not now clear.
A noticeable feature of the suture line is its deeply cleft siphonal saddle and its
asymmetry, the divisions on the right aide being smaller and less developed. This
lack of symmetry runs through the family and cstenda toother elements of the suture
line, but to what extent is not yet fully known. In some apecies the left side ahowa
the Ie3s developed sutures, but whether these are individual or accidental features ia
not yet known. Suture lines representing a few of the species will be given.
Acanthoplilet gardneri Anderson, n. Bp.
(Plate ST, 8fui» I; pints £4, Scut* 1)
Shell large, moderately robust, with rather broad umbilicus and numerous welldeveloped
ribs, the holotype possessing 56 to the whorl; involution nearly one-third;
transverse section somewhat elliptical, as shown in tha figure; ribs of two ranks,
alternately primary and secondary; primary ribs arise on the abrupt umbilical walla
in Btout ridges eloping backward up to the rounded umbilical border, from which
they pass upward in a slightly sigmoid curve to the ventral zone, which they cross
-without interruption or diminution; a few of the primary ribs bifurcate a little below
the middle of tbe side; secondary ribs arise near the middle of the aide and cross the
ventral zone as do the others.
In transverse section the shell is somewhat compressed, the sides being Battened
near the middle; it thus differs from the convex form of the preceding species; the
ribs are also narrower and more numerous than in AeantAopfiies remondi, but are
rounded in form and are apparently without tubercules at any stage. The suture
line is not unlike that of .4. remondi, having the siphonal saddle deeply cleft by an
oblique incision, from which an asymmetry of the line begins, the right side being the
leas developed. Whether this asymmetry results from habitual position on the sea
floor is not known.
The holotype (Calif. Acad. Sci. type Coll.) has the following dimensions: greatest