LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

PARTH PALEONTOLOGY
DESCRIPTION OP SPECIES
GENERAL STATEMENT
The following descriptions by the writer recognize and adopt the results
of earlier workers as far as possible without dwelling upon their errors.
Many of the descriptions are based upon older holotypes whenever obtainable,
although in some cases this has not seemed necessary. Search
has been made in the £eld for topotypes of species described from the
Shasta series, if their holotypes have not been available, and for the horizons
represented by them. From the study of the field and its sequence
of faunas it is now possible to state more precisely tbe horizons, if not the
localities, from which the original types were obtained. In the descriptions
of species given by Gabb (1869b) there is often little information as
to their stratigraphic position, and this fact has been a source of much
uncertainty, and in some cases confusion. In the present work this confusion
is in part removed, although much remains to be added by later
explorations and more careful collecting and zoning.
There are few collections at hand from the Cretaceous of Europe and
other regions for comparative study and the descriptions of the fossil
materials now available. For this reason it has been necessary to rely
largely upon published figures and descriptions found in the literature of
various countries. In some cases this method has been fairly satisfactory;
in other cases much doubt has been felt. In many cases, however, the
sequence of faunas in the Shasta series and their correlations have afforded
some confidence and have aided somewhat in the determination of genera
and species.
In the matter of taxonomy it has been the writer's purpose to be conservative,
rather than over progressive, and for this reason he has been
reluctant to adopt many innovations that have seemed to be only theoretical,
or experimental, and incapable of satisfactory proof. On tbe other
hand, in a few cases, after long and seemingly exhaustive search for appropriate
genera in which to include certain forms, it has seemed to be
necessary to propose new generic groups for their reception.
In the matter of families it has been found that the usage of Spath
(1924), or of Whitebouse (1926) has seemed to meet most of the requirements
of the cephalopod groups found in the Shasta scries, and as far as
possible these have been adopted.
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