Arkell.1956.Jurassic..

JAPAN AND KOREA 429
are compared with those used by Mori (1949) and Matsumoto & Ono
(1951 MS.) in different areas. Shiida (1940) has a completely different
set of names based on another area.
From the Sodenohama formation Professor Matsumoto collected a
Perisphinctid which could be an Aulacosphinctoides, and Aulacosphinctoides
cf. steigeri (Shim.) is recorded from the Hashiura area (Mori, 1949, p. 319).
From the Arato formation, sensu stricto, Professor Matsumoto showed me
two Parkinsonia-likc ammonites which seem to me to be Idoceras spp.
allied to Mexican forms of the Lower Kimeridgian. From the Arato
Shale, sensu lato, Mori (1949) records Kimeridgian and Upper Oxfordian
ammonites. Among Upper Oxfordian Perisphinctids recorded are
Kranaosphinctes cf. matsushimai (Yok.), Perisphinctes s.s. ozikaensis (Fukada,
Locality Hashiura Generalised Locality Shizukawa
(Mori, 1949) (Mabuti, 1933) (Matsumoto & Ono)
c. 1000 m. c. 1000 m. 700 m.
Jusanhama Group, 300 m. Tukihame Sandstone,
(? Tithonian) 200 m.
Hashiura Group, 600 m. Arato Shale sensu lato, Sodenohama Formation,
>520 m. c. 200 m.
slight unconformity Arato Formation, sensu
stricto, 300 m.
Aratosaki Sandstone, Aratozaki Formation,
200 m. 60-100 m.
Shizukawa Group, 90-110 m. Hosoura Sandy Shale, Hosoura Formation,
30 m. 60-100 m.
Niranohama Beds, 40 m. Niranohama Formation,
80-100 m.
1950) and Discosphinctes (Kobayashi & Fukada, 1947c; but the published
fragments are not really determinable with finality). Fukada states that
there is a sequence of Upper Oxfordian Perisphinctids which indicates
that the English Corallian Beds are condensed. Posidonia beds occur,
and Seymourites has been recorded.
Liassic stages from Hettangian to Upper Toarcian are represented
among the ammonites recorded from the Hosoura formation. They
include Hettangian Schlotheimia (Yokoyama, 1904a, pi. i, fig. 6), Sinemurian
Asteroceras and Oxynoticeras (Matsumoto & Ono MS., and see
Yokoyama, 1904a, pi. ii, fig. 11), various Toarcian Harpoceratids and the
Upper Toarcian Phymatoceras chibai (Yokoyama sp., 1915, pi.). Recently
Tmetoceras has also been figured (Sato, 1954), so Lower Bajocian is
present.
From the Niranohama formation, Matsumoto & Ono record 'a single
well-preserved Alsatites', with many Trigoniae and other pelecypods;
belemnites and corals also occur, and there are poorly-preserved
plants.
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