Arkell.1956.Jurassic..

u8 WESTERN GERMANY
and Athleta Beds of Model. Spath (1949) showed that only Model's beds
2-6 are Upper Callovian, with a total thickness of 3-1 m., and he attempted
to distinguish Athleta and Lamberti Zones on the basis of Model's collection
now in the British Museum. In some places in the Swabian Alb
the Lamberti Zone is represented in the nodule bed, for typical Quenstedtoceras
cf. lamberti, in preservation too perfect to be derived, are found
in the nodules, whereas in other places similar nodules yield typical
Cardioceras of the Cordatum Zone (Quenstedt, 1887, pi. 90, figs. 8, 10).
MIDDLE AND LOWER CALLOVIAN (up to 45 m.)
The maximum thickness of 45 m. is reached in the Lochen district
(Fischer, 1913, p. 27) but it is usually much less. In Franconia about
10 m. of Ornatenton underlain by a thin Macrocephalenbank is normal.
For richness of faunas and beauty of preservation, this Middle and Lower
Callovian may be unrivalled, but owing mainly to ambiguities of nomenclature
and poverty of clear exposures it is difficult to obtain an accurate
picture of the ammonite sequence. From the work of Reuter (1908,
1910, 1927) the succession at least in Franconia seemed simple, but the
more intensive work of Dorn (1916, 1922), Model (1914, 1916, 1935),
Model & Kuhn (1935) and Kuhn (1935, 1939) revealed an unsuspected
wealth of ammonites and complexity of distribution, and caused Model
(in Model & Kuhn, 1935, p. 468) to repudiate the scheme of facieschanges
worked out by Reuter (1908).
It is impossible here to summarize or even comment usefully on Model's
and Model & Kuhn's detailed and valuable records and discussions of the
ammonites, even though large numbers have since been figured by Kuhn
(1939). The basic difficulties in using these figures are, first, that most
come from the famous Goldschnecken clays, in which only septate inner
whorls are preserved, and, secondly, that few are figured in ventral view
or with whorl-sections.
Detailed correlation with England bristles with difficulties. For
instance, Kosmoceras jason is recorded from as low as the Parapatoceras
bed to as high as the obductum bed, and the specimen figured by Kuhn
(1939, pi. i, fig. 8) is more like the nucleus of a gulielmi or stutchburii.
Reineckeia anceps is recorded from immediately above the Parapatoceras
bed, associated with Macrocephalites and Sigaloceras, a position substantially
lower than would be expected if it is the same species as that in the
main anceps level higher up. The 'calloviensis' of the Calloviensis-
Enodatum Zone is according to Model & Kuhn (1935, p. 476) 'coarsely
ribbed thick forms which seem to go back to Kepplerites keppleri', and
therefore can hardly belong to Hyatt's genus Sigaloceras, while commonest
in the upper Utzing beds is Catasigaloceras Buckman, which denotes a
higher horizon (Planicerclus Subzone); and the two nuclei figured as
S. calloviense by Kuhn (1939, pi. i, figs. 5, 7) appear to belong to Kepplerites
(gowerianus group). Some records of S. calloviense probably refer to
S. franconicum See (type K. cf. calloviensis Reuter, 1908, p. 99, fig.).
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