Arkell.1956.Jurassic..

112 WESTERN GERMANY
is a distinct zone separable from the Ciliate Zone (Roll, 1933, pp. 555-6).
More work is required on this problem, as Roll remarked.
Zementmergel, 10-80 m. A constant formation that can be traced
throughout the Swabian and Franconian Alb except where locally cut
out by the unconformity below the Rennertshofen Beds (Roll, 1933, 1934).
Few ammonites known: Ochetoceras zio (Oppel) (Joos, 1945, p. 15).
Zone of Lithacoceras ulmense. Upper Ulmensis Beds, 30 m., and
Nattheim coral reef. Lithacoceras ulmense (Oppel) (type species of the
genus) has been fully discussed and refigured by Schneid (1914, p. 159,
pi. iv, fig. 3). The occurrence of Gravesiae in this zone is to be inferred
from the literature (but Roll's Ulmensis-Schichten, 1932, p. 184, include
the Plattenkalk of the Lithographicum Zone, and his records of Gravesia
gigas in the Hangende Bankkalke, above the Zementmergel, appear to be
negatived by his subsequent stratigraphical revisions in 1933, 19346, and
1935)-
Zone of Taramelliceras lithographicum. Solnhofen Plattenkalk, 8-60 m.;
locally the upper part shows submarine slump structures (Krumbeck,
1928). Ammonites and aptychi from the celebrated lithographic limestone
quarries of Solnhofen and Eichstatt were figured by Oppel (1863,
pis. 68-74). They include T. lithographicum (Oppel), Neochetoceras
steraspis (Oppel), Haploceras elimatum (Oppel), H. staszycii (Zeusch.)
(Neumayr, 1870, pi. xxiii, figs. 5, 7), Enosphinctes bracheri (Berckhemer),
Hybonoticeras hybonotum (Oppel; syn. autharis Oppel), Aspidoceras
hoplisum (Oppel), Physodoceras pipini (Oppel), Subplanites ruppellianus
(Quenst.) (Schneid, 1914, pi. iii, 3), Lithacoceras ulmense (Oppel) (ibid.,
pi. iv, 3), and a form that seems generically indistinguishable from true
Himalayan Virgatosphinctes, V. eystettensis Schneid (pi. iii, 5). Unfortunately
the records of Gravesiae do not make it absolutely certain that any
have been found in this zone (see Roll, 1932, p. 185).
Zone of Hybonoticeras beckeri. This zonal index, proposed by Neumayr
in 1873, seems appropriate for the various limestones and dolomites,
from at least 50 to more than 100 m. thick, separating the Lithographicum
Zone from the Pseudomutabilis Zone. The latter was included in the
Beckeri Zone by Neumayr, but beckeri and its associates do not occur in
the Pseudomutabilis Zone where that is palaeontologically recognizable.
Lithologically it is often impossible to distinguish the two zones. The
whole comprises a variety of facies—Massenkalk, Felsenkalk, dolomite
and Diceras and sponge limestones, altogether exceeding 200 m. The
Kelheim Diceras Limestone probably comes in the upper part of the
Beckeri Zone, but its figured ammonites (Schlosser, 1882) are peculiar
and have not been fitted into the sequence elsewhere (see Schneid, 1914,
p. 133). Three subzones are recognized, as follows (Berckhemer, 1922;
Roll, 1932, 19346):
Subzone of Lithacoceras siliceum (Quenst.), with Taramelliceras zvepferi
(Berck.), T. vermiculare (Quenst.), Ochetoceras zio (Oppel), Enosphinctes
rebholzi (Berck.) and ? Hybonoticeras beckeri (Neum.).
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