Arkell.1956.Jurassic..

92 THE JURA MOUNTAINS
Anderson, who confirms Carozzi's dating. Collections from about 4 m.
above the base of the Purbeckian at localities near the NW. shore of
Lake Neuchatel consisted up to 95 per cent, of Candona bononiensis
Jones and corresponded to assemblages from the upper part of the
English Lower Purbeck (Anderson, 1951). Mr Anderson informs me
(in lit., 1953) that the 'Intercalation marine' in the middle freshwater
beds is of the date of the marine beds in the Middle Purbeck, and that
so far there is no evidence for the upper part of the Upper Purbeck.
The mollusca comprise many of the same brackish and freshwater
genera as in the English Purbeck; in particular there are seven and
perhaps ten species of freshwater gastropods, including Valvata, Hydrobia,
Planorbis, Physa, Lymnaea, Viviparus and Ellobium.
PORTLANDIAN ? AND UPPER AND MIDDLE KIMERIDGIAN (50-150 m.)
In Randen and the NE. Jura, Plattenkalke, 30-70 m. thick (where not
removed by erosion), have long been recognized as belonging to Oppel's
Steraspis Zone of Bavaria, on the strength of yielding Streblites (Neochetoceras)
steraspis (Oppel), Glochiceras thoro (Oppel), Lithacoceras
ulmense (Oppel), Aspidoceras hoplisum (Oppel) and A. cf. longispinum
(Sow.) (Moesch, 1867, pp. 201-6). In the central and southern Jura,
where a succession would be especially welcome because of the presence
of freshwater Purbeck Beds, there is a considerable thickening, with
passage into dolomites and crystalline or compact limestones difficult
to separate from the Purbeckian, but ammonites appear only in the
lower part of the series, which reaches a maximum of 150 m. The species
recorded are Gravesia portlandica (de Lor.), G. irius (d'Orb.) and G.
gravesiana (d'Orb.) (Salfeld, 1914, p. 227; Heim, 1919, table, p. 506),
and (underlying beds with the first two in Bugey, at the south extremity
of the Jura), Neochetoceras steraspis Oppel sp. (Pelletier, 1953).
LOWER KIMERIDGIAN (c. 25-250 m.)
Zone of Aulacostephanus pseudomutabilis. Wettingen Beds, etc.:
compact and siliceous limestones, marls and limestones with Exogyra
virgula, passing into white chalky Z)jceras-limestones at Montbeliard
(Contejean, 1859) and into 143 m. of white coral reef limestone at Mont
Saleve and possibly 40 m. of limestone with chert nodules below. The
celebrated coral reefs of Valfin are also in this zone. From the Wettingen
Beds are recorded Aulacostephanus eudoxus (d'Orb.), A. pseudomutabilis
(de Lor.), Glochiceras nimbatum (Oppel), Taramelliceras trachinotum
(Oppel), T. holbeini (Oppel) and Orthaspidoceras orthocera (d'Orb.)
(Moesch, 1867, pp. 193-201; Heim, 1919, p. 506, table).
Zone of Streblites tenuilobatus, Baden Beds, 6-150 m. Marly limestones
with a very rich ammonite and other fauna monographed by
de Loriol (1876-78, 1880-81) and Butticaz (1943). These monographs
show a striking mixture of NW. European and Tethyan ammonites.
Northern elements are Amoeboceras kapfi (Oppel) and the many Raseniae
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