Arkell.1956.Jurassic..

332 EAST AFRICA
KIMERIDGIAN
The upper part of the thick mass of yellowish marls with septaria yields
in abundance, preserved in the septaria, an assemblage of Pachysphinctes
and Aspidoceras monographed by Dietrich (1925) from an outcrop on the
Mahokondo stream, 25 km. NW. of Kiswere harbour. Collections of
these ammonites, in the same preservation, were sent me by Mr Aitken
and by Dr Kent from the vicinity of Nchia village and river (a tributary
of the Mandawa). Dietrich handled over 200 Perisphinctids and over
100 Aspidoceratids from Mahokondo and remarked that these two genera
greatly predominate over all other forms, but that besides some other
ammonites there were pelecypods, brachiopods, Crustacea and drift wood,
indicating a neritic environment. The full list of ammonites, incorporating
some nomenclatural revisions, is as follows:—
Lytoceras aff. fraasi Dacque
Phylloceras cf. subplicatius Burckhardt
Ptychophylloceras ptychoicum (Quenst.)
Holcophylloceras mesolcum (Dietrich)
Glochiceras aff. fialar (Oppel)
Taramelliceras cf. compsum (Oppel)
Taramelliceras cf. harpoceroides Burckhardt
Streblites futtereri (Miiller)
Streblites cf. planopicta Dietrich (non Uhlig?)
Pachysphinctes africogermanus Dietrich
Pachysphinctes mahokondobeyrichi (Dietrich)
Pachysphinctes recki Dietrich
Pachysphinctes mulleri Burckhardt (= P. elizabethae Miiller non de
Riaz)
'Idoceras' mahokondobalderus Dietrich (gen. indet.)
Nebrodites aethiopicoherbichi Dietrich
Aspidoceras richthofeni Miiller (= A. kilindinianum Dacque)
As Dietrich rightly perceived; this is a fauna of the Mutabilis and/or
Pseudomutabilis Zones (Lower Kimeridgian).
UPPER OXFORDIAN
From the top of the underlying beds, a varied sequence of sandstones,
marls and sandy limestones, 180 m. thick, Mr Aitken has collected a large,
well-preserved Perisphinctes (Arisphinctes) maximus (Young & Bird),
tending towards P. (A.) cotovui Simionescu, and Perisphinctes orientalis
Siem, P. cf. ingens (Y. & B.), P. antecedens Salf., P. wartae Buk., P. cf.
dobrogensis Sim., Euaspidoceras depressum (Fut.) and a Mayaitid; ah
assemblage which gives a firm dating to the Plicatilis Zone.
MIDDLE CALLOVIAN
At various localities on the several rivers that unite to form the Mandawa
River, and at a lower level in the series, Aitken collected well-preserved
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