Arkell.1956.Jurassic..

422 JAPAN AND KOREA
species of tricarinate Fuciniceras and Protogrammoceras. 'Pseudogrammoceras
nakayamense' Matsumoto (their pi. i, figs. 4, 5) shows three strong
keels and seems specifically indistinguishable from Fuciniceras lavinianum
(Men.) the type species of Fuciniceras. The type specimen of 'Grammoceras'
nipponicum Matsumoto (pi. ii, fig. 3) is probably a distinct species,
but some smaller specimens sent me as varieties of it seem indistinguishable
from Italian species such as Protogrammoceras isseli (Fucini) and P.
inseparabilis (Fucini). These forms, originally supposed by Fucini to
be Domerian, are found in Japan in company with Lioceratoides (pi. i,
fig. 9) (= 'Praelioceras' Fucini) and Harpoceras okadai (Yokayama, 1904)
(pi. i, fig. 8) which seems identical with H. praeplanatum Fucini (1924)
and hardly distinguishable from involute forms of the common Whitby
Toarcian Harpoceras exaratum (Young & Bird), and Toarcian forms such
as Hildoceras densicostatum Yok. and Dactylioceras helianthoides Yok.
From the close resemblance of the last to Dactylioceras tenuicostatum
(Young & Bird) and its upward range into the typical Commune and
Falcifer assemblage of bed Nd, the assemblage of bed Ng can only be
placed at the base of the Toarcian.
The mixture of Italian and English elements in the underlying Upper
Pliensbachian beds (Ne) is instructive.
At various horizons in the Toyora group there is an extensive flora
allied to floras usually considered Upper Jurassic elsewhere; and in the
Utano formation are two endemic species of Inoceramus (Kobayashi,
1926, with plate). Above the Utano formation Kobayashi included a
further series of sandstones and shales (Nanami formation) with plants
only, which Matsumoto & Ono consider partly a lateral equivalent of the
Utano formation and partly the Toyonishi group, mentioned below.
The Jurassic Toyora Group is overlain disconformably, and locally
unconformably, by conglomerate and coarse pebbly sandstone, which
pass up into a further group of sandstones, shales and conglomerates, the
Toyonishi Group, of Lower Cretaceous and perhaps Upper Jurassic
age (Matsumoto, 1949, 1954). In the upper part of the group are the
Yoshimo Beds, with a brackish-water fauna of pelecypods and gastropods.
They include early Corbiculids and large Turritellid gastropods suggestive
of the Aptian Cassiope of Spain (Kobayashi & Suzuki, 1939). These beds
are unconformably overlain by equivalents of the Wakino formation
(see below) and Inkstone Group of the Lower Cretaceous, with igneous
rocks (Matsumoto, editor, 1954). Kobayashi (1938) considered the
Inkstone Series Upper Neocomian and the Yoshimo Beds Wealden.
NORTHERN KYUSHU
About 50 miles to the south-west, near the university town of Fukuoka,
on the north end of the island of Kyushu, the Cretaceous Inkstone Series,
with green tuff and altered andesites, overlies the Wakino Series. This
latter consists of 800 m. of black shale overlying up to 150 m. of conglomerate.
Below are much older rocks, undated (Kobayashi & Ota,
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