Arkell.1956.Jurassic..

n6 WESTERN GERMANY
Pomerania. Amoeboceras bauhini (Oppel), A. lineatum (Qu.), A. subtilecaelatum
(Font.), A. schlosseri (Wegele) range from the Planula Subzone
into the Platynota subzone.
Subzone of Epipeltoceras bimammatum s.s. This subzone is the principal
source of Ringsteadiae, which are commonest around the junction between
alpha and beta and in lower beta. None agrees exactly with English and
NW. German species, but forms close to R. frequens Salf., R. brandesi
Salf. and R. pseudo-yo Salf. occur, with R. limosa Quenstedt sp. (1888,
pi. 124, fig. 3) (P. Dorn, 1925; Dieterich, 1940, p. 35). This is also the
home of Orthosphinctes tiziani (Oppel), O. polygyratus (Rein.) and O.
laufenensis (Siemiradzki) (Wegele, 1929, pi. i, figs. 4-6; Dieterich, 1940,
pi. ii, fig. 8). In the fossil-beds at Lochengrundle cutting (see Fischer,
1913, pp. 34-7) the commonest of the many small ammonites is perhaps
Amoeboceras ovale (Quenst.), which is replaced in the lower part of beta
by A. lorioli (Oppenheimer) and A. bauhini (Oppel). (For figures of these
and later Amoeboceras see Fischer, 1913a, whose determinations are
corrected by Salfeld, 1915; and Wegele, 1929, pi. iv). In presumed
equivalents of the Lochen Beds in Franconia Epipeltoceras berrense (Favre)
is said to attain its maximum, but it also occurs in the underlying
'Hypselum Zone', with the closely allied E. circumcostatum (Dorn) and
E. retrocostatum (Dorn).
It is not clear whether this Franconian zone of Euaspidoceras hypselum
(Oppel) and Epipeltoceras uhligi (Oppenheimer) should be regarded as a
lower part of the Bimammatum Zone or as equivalent to the Alternans
Subzone (P. Dorn, 1925, 1930). Its ammonites are, however, much more
allied to those of the Bimammatum Zone than to those of the Transversarium
Zone: they include Amoeboceras ovale (Quenst.), A. subcot-datum
(d'Orb.), Prionodoceras sp. (Dorn, 1930, pi. xxxv, fig. 2—quite different
from fig. 1), Euaspidoceras linki (C. Dorn), E. costatum (C. Dorn) (1923)
and various Taramelliceras, but there are also still Ochetoceras canaliculatum
(von Buch) and Amoeboceras aff. alternans (von Buch). Perisphinctes
(Microbiplices) microbiplex (Quenst.), said to be common in the
Hypselum Zone (P. Dorn, 1930, p. 161), occurs in England only in the
zone of Ringsteadia pseudocordata and is therefore an indicator of a high
horizon.
Zone of Gregoryceras transversarium (up to c. 100 m.). Between the
Lochen Beds with E. bimammatum and its allies and the true Transversarium
Beds in Swabia lie up to 90 m. of marly beds formerly called
the Impressa Marls (or Clays), which Salfeld (1913, p. 179) called the
Zone of Amoeboceras alternans (see Salfeld, 1915, p. 163, pi. xvi). The
upper part, exposed in Lochengrundle cutting, has already been transferred
to the Bimammatum Zone. In the rest ammonites are much scarcer, and
it is still doubtful with what these beds should be compared. If they are
to be correlated with the Franconian 'Hypselum Zone' just mentioned,
they should be classed with the Bimammatum Zone. On the other hand,
the evidence for this is inadequate, and it must be borne in mind that
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