LOWER CRETACEOUS DEPOSITS CALIFORNIA AND OREGON

102 LOWEB CBETACEQUS DEPOSITS IN CALtFOSKIA AND OHEGON
rata. In Ma discussiou of tho types included % him under this name Stanton
(1896, p. 45) says, in part;
"This description is meant to include all the robust varieties of Aucella that art
characteristic of tbe upper part of tbe Knoxville beds in California, ranging through
perhaps I50G to 2000 feet Of strata."
As attempt has recently been mads to discredit the generic name AvcHLa, and
to replace it by "B^cAta," a name proposed by ftouillier in 1835. Whatever claim
may now be made by anyone for the validity of "Buehia" upon the basis of priority,
tho fact is evident that most specialists, sinco KeyBerling's time, have accepted the
name Aucelta, as defined by him, and this name has now, after more than BO years
of use, become BO well established in the literature that no rule should be invoked
to replace it. It would seem that the question bad been sufficiently settled by
Pompeckj (1501) but for those who mu.y still be unconvinced, it may be recalled that
Rouillier gave neither figure, description, nor any characterization of the species
upon which he proposed to found tho name "Bwhxa," but merely submitted to his
society an etampla of a shell which he believed to be "Asieuia mo&quen&it" Buch.
Whether this shell was properly identified by him, we have no means of knowing.
For this reason the name "Buchia," as remarked by Pompeckj, "did not meet with
approval, as opposed to the name Aucella and ita better characterisation provided
by Graf Keyseriing for the new genus."
Ia the Lower Cretaceous deposits of Russia many forma of Aucella have been
distinguished by specific names given by Keyserling (1M8-1&4&), L&Iiuscn (1888)
and Pompeckj (1001), a general review of which has been given by A. P. Pavlow
(1907). In this review of the succession of AuetUat found in the Upper Jurassic and
Lower Cretaceous of Russia, and in contemporary beds in California, and with the
aid of fossils obtained by him from this state, Pavlow was able to show marked
parallelism in the atrfl.tigra.phic occurrences of species common to both regions, and
also many analogous forms. Others have since been discovered. Had Pavlow bean
able to obtain complete suites of Aucella from the Knoxville and Shasta series in
California, this parallelism would probably have been extended farther. In addition
to the more robust forma found in the Shasta series, a few smaller species have
been found, but none can be identified with species characteristic of the Knoxville
series. Some difficulty is often found in identifying the immature shells of closely
related apecies, but less is found in the separation of adult shells, and in this fact
they follow tbe rule of many other genera.
The atmtigraphioal occurrence of tbe several forms of Avcclla found in the Paskenta
group is about as follows, although there are some overlaps:
Upper third—aonc of Dithotpmiita—A-Mxlla erainricollia Koyserling, .4. crewta
Pavlow, A., lembratuloidet Lahusen;
Middle third—zone of JVcocomi^a and Berriaeclla—Aucella -piriformis Lsliu&en,
A. kcyicrlinffi Labuaen, A, nucijormit Pavlow;
Lower third—zone of Phyllaeerai cf. Knoxvillense—Avcclla lalida Lahusea,
A. uncttoi'dei Pavlow, A. i-nfiala Toula, A. laftttscni Pavlow, and A, rtuctfarmis
Pavlow, the last occurring in two distinct zones, although not
abundant in either.
It is not known whether this succession will be found in all sections, but at present
it appears to maintain throughout the districts south of the delta.
The occurrence of Aucella •piathi Gabb, or some related species, in the lower part
of the Shasta series has been claimed by aotne, but this claim should be accepted with
reserve. It may be based upon a misinterpretation of young forma of other species—
e.g., A. lahvaeni Pavlow, or of the strata containing it, or both.