LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

description of species 217
The holotype of this species, a fragment of the body-chamber only, is in the
Museum of Paleontology, University of California. More complete examples of the
same species have been obtained from Alderson Creek and have been compared with
tbe holotype. The shell is small, with limbs not closely approximate; the smaller
limb has a subcircular section, and that of the larger limb is more nearly circular;
both limbs are costate; the ribs on the smaller limb are much more oblique than those
of the other; ribs without pronounced ornament, more elevated on the ventral surface;
on the smaller limb the ribs are less prominent and the interspaces shallow;
gome of the riba on the smaller limb bear faint nodes on the ventral border, but they
croea the ventral zone without interruption. The figured specimen (Calif. Acad.
Sci, type Coll.) was found on Alderson Creek, in the Alderson zona, associated with
Lyloceraa bale ax (Traak) and Phyllocerat aldersoni nov, CSabb's statement that
' 'from one imperfect impression, showing 2fi ribs, it seems that on a single rib there
have been two tubercules, or spines, one near the dorsal and the othor near the ventral
aide," did not refer to hia holotype, but to some other specimen not figured. Faint
nodes are found on tbe ventral border of the smaller limb only, as already noted.
Toxaceras d'Orbigny
Toxoeertu cornueapri Anderson, a. sp.
(Flits it,
Shell small, openly curved, tapering somewhat regularly, transversely costate,
with rounded ribs, most of which bear Bmall, inconspicuous spines on the ventral
border and a lesser number on the side of the shell; the ventro-lateral spines are
somewhat more prominent than the lateral; the lateral spines seen only at irregular
intervals. The curvature of the abell increases gradually with growth, the shell
being almost straight at first but curving more rapidly toward the bucal end. This
shell resembles Toxoceras cmericianum. d'Orbigny from Vergons (Bassea-Alpes),
France. The holotype (Calif. Inat. Tech. Coll.) haa the following dimensions:
length of cone (incomplete), 67 mm.; ventro-dorsal width, 8 mm,; transverse thickness,
7 mm.
This example was found by W. P. Popenoe and D, W. Sehsrf on Alderson Creek,
half a mile southeast of the Barr ranch house, south of Ono. Its position appears to
he below the Argonaut zone of the Alderson Creek section. Ita locality number ia
969 (Calif. Inst. Tech.) and is not known to have had associates of other apecies.
HAUrnDAE Hyatt, emend. Spath, 1922
Although Spath has included in this family many later Cretaceous types, only a
brief consideration is here given the pre-Cenom&nian, costate, and non-tuberculate
bamitids, and a single tuherculate form that cannot well be omitted from the list.
The family is here regarded aa including the following;
Hamitee Parkinson; genotype, IIamitee altenutUut Sowerby (not d'Orbigny)
Tornutoeerae Hyatt; genotype, Hamilea altenuaixie d'Orbigny (not Sowerby)
Helicoceras d'Orbigny; genotype, "BamiUs" annulatwi d'Orbigny
Plyeheteeras d'Orbigny; genotype, PtychocErait gaultianum (Pictet)
Whitehouse (1920, p. 321-226) has questioned the practical value of Tornuiocerat
AS a generic term; he believes that the forms placed under it may well be included
in Hamilee. It would appear also that along with Ptychoeeras d'Orbigny, it would be
permissible to include Diptychoeeraa Gabb; genotype, Diplychoceras laeve, and a moderately
tuherculate form, both of which arc found in the Perrin 20ne of the Hulen
beds in the Cottonwood district- The single unquestionable species of Hamitet
below tbe Cenomanian ia a rather large form found near the middle part of the Albian
and is represented by only a fragment of a shell.