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Arkell.1956.Jurassic..

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102 THE JURA MOUNTAINS<br />

by Lieb (1951, 1954). In the following summary all the species are<br />

Buckman's except where otherwise attributed.<br />

Zone of Graphoceras concavum, with G. concavum and numerous other<br />

Graphoceras spp., Brasilia, Reynesella, Eudmetoceras amplectens, E.<br />

infernense, E. euaptetum. A distinct horizon at base of the zone contains<br />

a mixture of Graphoceras, some of which occur in the Concavum Zone,<br />

others in the Bradfordensis Subzone in England.<br />

Zones<br />

(with dates proposed)<br />

Graphoceras concavum<br />

(Buckman, 1890, Haug,<br />

1891)<br />

Ludwigia murchisonae<br />

(Oppel, 1856)<br />

Tmetoceras scissum<br />

(Neumayr, 1871,<br />

emended<br />

Buckman, 1898)<br />

Leioceras opalinum<br />

(Brauns, 1864)<br />

TABLE 8.—THE LOWER BAJOCIAN IN THE NORTHERN JURA<br />

Subzones in the Jura<br />

(Lieb)<br />

Graphoceras concavum<br />

(and 'praeconcava')<br />

Brasilia bradfordensis<br />

(Buckman, 1893)<br />

Staufenia staufensis<br />

(Hoffmann, 1910)<br />

Costil'eioceras discoideum<br />

(Hoffmann, 1913)<br />

Tmetoceras scissum<br />

(with Costileioceras<br />

sinon)<br />

Leioceras opalinum<br />

(with Costileioceras<br />

costosum)<br />

_^NW.<br />

Germany<br />

(Hoffmann)<br />

England<br />

concavum concavum<br />

murchisonae<br />

bradfordensis<br />

staufensis murchisonae<br />

murchisonae<br />

discoideum<br />

sehndense<br />

tolutarium<br />

sinon<br />

(Hoffmann,<br />

1910)<br />

costosum<br />

opalinum<br />

'Ancolioceras'<br />

'Ancolioceras'<br />

and/or and/or gap<br />

gap<br />

scissum<br />

scissum<br />

opalinum<br />

opalinum<br />

('opaliniforme')<br />

('opaliniforme')<br />

Zone of Ludwigia murchisonae.<br />

Subzone of Brasilia bradfordensis, with B. bradfordensis, B. platychora,<br />

B. subcornuta, Ludwigia falcata, L. similis, L. wilsoni, Graphoceras impolitum,<br />

Staufenia staufensis Oppel sp. (rare).<br />

Subzone of Staufenia staufensis. About 4-5 m. below the foregoing<br />

ammonite bed at Duntelen is a horizon with rather common S. staufensis<br />

(Oppel), as in Germany.<br />

Subzone of Costileioceras discoideum (Qu.), which combines Hoffmann's<br />

subzones of C. discoideum, C. sehndense and C. tolutarium in Germany<br />

and already contains Ludwigia murchisonae, as in the Swabian Jura (see<br />

p. 125). Since Costileioceras tolutarium (Dumortier) occurs in England<br />

in the Scissum Zone, this condensed Swiss zone apparently embraces<br />

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