Arkell.1956.Jurassic..

TELLIAN ATLAS AND PLATEAU OF THE SHOTTS 279
in abundance from NE. Morocco (Daguin, 1927; Gentil, 1908, 1908a;
Agard, Termier & Termier, 1950) through the Oudjda and Ghar Rouban
areas (Lucas, 1942), the Saida area (Dubar, 1932) and Jebel Nador
(Deleau, 1941, 1948), the Djurdjura (Roman & Russo, 1948, p. 14), eastern
Algeria (Savornin, 1920, pp. 140, 147; Ehrmann, 1942; Deleau, 1938,
pp. 80, 90) and Tunisia (Solignac, 1947, facing p. 14). At least three
successive zones can be recognized, of which the lowest is known separately
only in the Djurdjura, where there is a level with Dactylioceras athleticum
(Simpson) as in the Middle Atlas, corresponding to the Tenuicostatum
Zone.
By far the most abundant and widespread fauna is that of the Falcifer
and Commune Zones, which comprises the Italian fauna and is usually
developed in the Italian and Alpine facies of ammonitico rosso, but
sometimes as clays with pyritic fossils. The ammonites are too numerous
to be listed and are for the most part the same as those already enumerated
from the Moroccan Atlas. An interesting addition at Jebel Nador is
Leukadiella ionica Renz, a species previously known only in the Toarcian
of Greece (Deleau, 1948, pi. ii, fig. 30, wrongly called Bouleiceras nitescens
Thevenin). The Upper Toarcian fauna is less abundant but has an
equally wide distribution from Morocco to the Djurdjura, and has usually
been separated by collectors. Lists are published by the authors cited
above. (See especially Lucas, 1942, pp. 239-40; Agard, Termier &
Termier, 1950).
UPPER PLIENSBACHIAN
This is co-extensive with the Toarcian but often less favourable for
collecting. The thickness varies from 10-70 m. on the belt of horsts to at
least 300 m. in the troughs of deposition, where there are thick dolomites
of Rif facies (Russo, 1935; Lucas, 1942, p. 184). The ammonite fauna
is essentially Italian, comprising many Domerian Arieticeras, Protogrammoceras,
Fuciniceras, etc. (Lists will be found in Lucas, 1942, and
other papers mentioned under the Toarcian; for critical revisions see
Roman & Russo, 1948, and Deleau, 1938, pp. 79-80, 90 ff.; and for figures
see Spath, 1913, pi. Iii; Deleau, 1938, pi. vi; Deleau, 1948, pi. i.) The
brachiopods of Guelma (between Bone and Constantine) have been studied
by Dareste de la Chavanne (1920).
LOWER PLIENSBACHIAN
With the Toarcian and Domerian fauna of the Djurdjura were collected
some Tropidoceras, Phylloceratids, etc. (Roman & Russo, 1948, p. 14).
Elsewhere strata of this age, if present, are without ammonites so far as
known; at Tourirt, for instance, their place is occupied by dolomites and
hard limestones with chert, yielding brachiopods (Agard, Termier &
Termier, 1950). At Jebel Nador also there are dolomites, and in eastern
Algeria compact limestones and oolites (Deleau, 1938, p. 90).
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