On
the
occurrence
of
Ste加用anella
(Ｙｅｈａｒella）
ｊａｐｏｎｉｃａ obｓｏはαＫＯＢＡＹＡsＨｌ
and
Amano,
from
Amakusa-Shimoiima
Island,
Kyushu
Masajoiki Tashiro
Ｄ砂ａｒｔｍｅｎt ０／ Ｇｅｏｌｏｇｙ. Facilitｙ ｏｆ Ｓｃｉｅｎｃｅｓ Ｋｏｃｈｉ Ｕｎｉ。ｅｒｓtり， Ｋｏｃｈｉ， ７８０， Ｊａｐａｎ
Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｉａｂｏｎｉｃａｏｂｓｏｌｅはKOBAYASHI and AMANO は, S. (7.)ｉａｂｏｎｉｃａ ｉａｂｏｎｉｃａ（ＹＥＨＡＲＡ）から由来したと思われる．後者は，四国地方の和泉層群や鹿児島甑島地 方，熊本天草下島西岸，牛深大島地方の姫浦層群上部亜層群のカンパニアン上部（ヘトナイ統下 部）から産するのに対し，本亜種は，甑島地方の姫浦層群上部亜層群のマストリヒツアンに知られ ている．今回，本亜種の標本を得た天草下島東岸部の白亜系は，天草下島西岸部とは，直接に連続 した分布を示さない．東岸部の本亜種産地と同層順にある二枚貝化石に富む砂岩層には，和泉層群 のマストリヒシアンに知られる二枚貝化石と共通するものがあることから，田代・野田(1973) は，この砂岩層をカンパニアン最上部かあるいはマストリヒシアンとし，鹿児島甑島の姫浦層群上 部亜層群上部層下部に対比している．甑島のこの部分からは，本亜種が多産することはすでに知ら れており，今回の本亜種の発見は，天草下島東岸部と甑島の白亜系の対比力≒適切であることを示 すばかりでなく，天草下島西岸部のＳ．（ｙ．）ｌａｐｏｎｉｃａ（ＹＥＨＡＲＡ）を産する部分との関係を知る 上にも重要である．．田代正之 Introduction
５ｌｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｉａｂｏｎｉｃａvar. obｓｏｌｅはKOBAYASHI and AMANO was described by KOBAYASHI and Amano (1955), from the Upper Cretaceous of the island of Taira of Koshikijima Area, Kagoshima Prefecture, as ａ ｖａｒｉｅＶｖ ｏ^ Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｍｂｏｎｉｃａ (Yehara). Recently this obsoleta was ranked up to ａ subspecies of S. (F.)ｊａｆｒｏｎｉｃａ （ＹＥＨＡＲＡ）ａｎｄ reported from the Lower Member of the Upper Formation of the Upper
Himenoura Subgroup (Member U-IIIa by Tashiro and NODA, 1973), distributed in the island of Shimo-Koshikiiima in Koshikiiima Area （TASHIR0 1976)｡
l report ｈｅｒｅ Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒｅｒlla）ｊａｐｏｎｉｃａｏｈｓｏｌｅtａKOBAYASH[ and AMANo, from Member U-IIIa of the Himenoura Group in Amakusa-Shimoiima, Kumamoto Prefecture. Further l describe this subspecies, and refer to significance about the occurrence of this subspecies in Amakusa-Shimoj i ma Island｡
Before going into my study, I wish to express my hearty thanks to proffesor Minoru Tamura of Kumamoto University, for his reading this manuscript and his continuous encouragements.
Stratigraphical
note .
The distribution of the Upper
Cretaceous system in Amakusa-Shimojima
Island, is
separat-ed the eastern-coast area (Miyanokawachi
Area)
and
the western-coast area (Oe
Area),
156 Res. Rep. Kochi Univ. vol. 27., Nat. Sci
each of which dose not continue one another. Several important fossils, e. g.,ＳｂｈｅｎｏｃｅｒａｒｒｉＭＳ ｓａｃｈｄｌｉｎｅれsis(Schmidt)， Ａｂｉｏtｒｉｇｏｎｉａ ｃｒａ％ｓｏｒａｄｉａは■nakano and Ｓtｅ伍ｍａｎｅｌｌａ（Ｙｅｈａｒella） ｊａｂｏｎｉｃａｍｂｏｎｉｃａ(YEHARA) , occur from the fossiliferous. sandstone near Oe in Oe Area
(Yehara, 1923a; TASHIRO and NODA, 1973). The age of the sandstone is Upper Camp an i an, judging from the inoceramids and trigonians. Onバhe other hand, several fossiliferous sandstones have also been reported from Miyanokawachi Area by many authors, Nakano (1957), Hatae (1960), TAKAI and ＢＯＪＯ（1?63), TASHIRO (1971, 1972, 1976), MiKl (1975), TASHIRO and NODA (1973) and MIKI ａｎｄトUEMATSU (1973). The sandstones of Miyanokawachi Area, however, do not yield aiiy inoceramids and ammonoides which are useful for age determination. Since such bivalve species as' ｊμ。かf即nia postonodosαNaka-NO, ＾ａｎｏｎａｖiｓ ａｔｖａｎａれｕｓ（ＩＣＨＩＫＡＷＡ and ＭＡＥＤＡ）, Ｌｉｍｏｂｓiｓ ｋｏｅａｉａ（ＩＣＨＩＫＡＷＡ and ＭＡＥＤＡ）， ｈｅｂtｏｓｏｌｅｎｉａｐｏｎｉｃａ（ＩＣＨＩＫＡＷＡ and MAEDA) and Loxo jabon俵1 (AMANO) which are known from Maestrichtian of the Izumi Group in Shikoku and Kii Areas, appear from the sandstones of Miyanokawachi Area, the geological age ｏれ the sandstones is probably Meastrichtian or Upper-most Campanian (TASHIRO and' NODA, 1973; Tashiro, 1976). The fossiliferous sandstone of Miyanokawachi Area were considered upper than the fossiliferous sandstone of Oe Area by Tashiro and NODA (1973). And･ they correlated the former with Member U-IIIa and the latter with Member U-IIa of the Upper Himenoura Subgroup in Koshikijima Area, Kagoshima Prefecture. ｡｡ ”
In the Koshikijima Area,Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｊａｂｏｎｉｃａ ｊａｂｏｎｉｃａ(Yehara) occurs abundantly from Member U-IIa, and s. (y.)ｊａｐｏｎｉｃａ ｏｂｓｏｉｅはKOBAYASHI and AMANO is also common in Member U-IIIa. These two subspecleｓ，' ｊａｂｏｎｉｃａａｎｄｏｂｓｏｌｅtａ.have not appeared in the same horizon, in sofar as ｌ know. The stratigraphical horizons of the locaitil-es of Ｓ. （ｙ.）ｉａｐｏｎｉｃａ ｏｈｓｏｌｅtａ Ｋ.OBAYASHI and AMANO in this paper, are nearly correlated with the fossiliferous sandstones of Miyanokawachi Area. The horizons are included in Member U-IIIa. The appearrence of S. (F.) ja知れtｅａ ｏｂsｏｌｅ!a KOBAYASHI and AMANO from Miyanokawachi Area of Amakusa-Shimojima Island, suggests the correctness of the correlation between the Upper Cretaceous of Amakusa-Shimojima Island and Koshikijima Area, also the horizons of this subspecies 。&s。leta being younger than that of the fossiliferous sandstone which was characterized by. S. (F.)ｉａｂｏｎｉｃａ ｉａｂｏｎｉｃａ(YEHARA) in Oe Area.
Distribution of Steinmanella (Teharella) jaj!onica ｓ. 1.
In sofar as l knew,Ｓteiれｍａれぶａ（Ｙｅｈａｒella）ｌａｂｏｎｉｃａ Ｊａ♪ｏｈｉｃａ（ＹＥＨＡＲＡ）iSpresented from the Izumi Group of Shikoku and the Ｕβper Himenb'ura Subgroup of South-western Kyushu. The localities in both groups are as follows.
-ｏ Kitadani, Prov. Sanuki･(Kagawa Prefecture); basal memりer of the Izumi Group. （ＹＥＨＡＲＡ， 1923b, 1931). ダ ・ ∧
ｏ Aonai, Yuyama-mura, Onsen-gun, Ehime Prefecture; basal sandstone and conglomerate beds of the Izumi Group. (KOBAYASHI and AMANO, 1955).
ｏ Himezuka of Dogo, Matsuyama City, Ehime Prefecture; basal pebbly mudstone of the Izumi Group; occurring together withＳｐｈｅｎｏｃｅｒａ？ｎｕｓｓｃｈｍｉｄti（ＭＩＣＨＡＥＬ）,Ａｂｉｏｌｒiｇｏｎiａ
On the occurrence ｏｆ Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella） obｓｏｌｅは (M.T.) 1ろ7
ＣΓａ％%ｏｒａｄｉ･ata NAKANO,Ｍｉｃｒｏtｒｉｇｏｎｉ･ａ ｉｍｕtｅｎｓis TASHIRO, Naれｏｎａｕtｓ hｒｅｖiｓ ICHIKAWA and maeda, ｅtＣ‥(ＮＯＤＡ and TASHIRO, (1973).
ｏ Kiyazaki, Matsuyama City, Ehime Prefecture; basal part of the Izutni Group. (the specimens are kept in the Museum of Matsuyama City).
ｏ Oemura, the west coast of Shimoshima, Prov. Hi go (Kumamoto Prefecture); Member U-IIa of the Upper Himenoura Subgroup ； occurring together with Sph.ｅｎｏｃｅｒａｍｕ％ ｓａｃｈａｌｉｎｅｎsis(ＳＣＨＭＩＤＴ)， Ａｐｉｏｌｒｉｇｏｎｉａ ｃｒａｓsｏｒａｄｉａtａNakano・Ｍｉｃｒｏtｒｉｇｏｎｉａ ｉｍｕtｅれｓiｓ Tashiro ，Ｎａｎｏれａｖi％ bｒｅｕfｓ ICHIKAWA and Maeda, etc.. (Yehara, 1923; Tashiro and NODA, 1973).
o Oshima islet, Ushibuka City, Kumamoto Prefecture; Member U-IIa of the Upper Hime- noura Subgroup; upper horizon thanがｂｈｅｎｏｃｅｒａｍｕｓ ｏｒｉｅｎtalｔｓｏｒienlalｔｓ(ＳＯＫＯＬＯＷ)ｚｏｎｅ in about 90 m thick, occurring together with Ｎａｎｏｎａｕtｓ bｒｅｘiiｓICHIKAWA and Maeda. (Hatae, 1960; Tashiro and NODA, 1973; TASHIRO, 1976).
ｏ Fukkireura, Shimo-Koshikijima, Satsuma-gun。Kagoshima Prefecture; Member U-IIa of the Upper Himenoura Subgroup; occurring together with Ｉｎｏｃｅｒａｍ.ｕ％ｅｌｅｇａｎｕｓｂｓｅｗｄｏsｕｌｃａtｕｓ Nagao and MATSUMOTO, Api。trigonia cΓα5sひΓadiata NAKANO, Ｍｉｃｒｏtｒtｇｏｎｉａ ｉｍｕtｅｎｓis Tashiro, etc.. (Tanaka and Teraoka, 1973; Tashiro and NODA, 1973; Tashiro, 1976)。
The localities of Steinmanella (Ｙｅｈａｒella）ｌａｂｏｎｉｃａ･obsｏＺｅはKOBAYASHI and AMANO, are only known in the Upper Himenoura Subgroup. They are as follows.
-ｏ Tairajima islet, Koshiki-jima Area, Satsuma-gun, Kagoshima Prefecture; Formation U-IV of the Upper Himenoura Subgroup; occurring together with G砂りｍ。ris (GtりｃｖＴＴｉｅｒitａ） ｊａｐｏｎｉｃａ ＴＡＳＨＩＲ０.（ＫＯＢＡＹＡＳＨｌ and ＡＭＡＮＯ√1955).
ｏ Imuta, Shimo-Koshikijima, Satsuma-gun, Kagoshima Prefecture: Member U-IIIa of the Upper Himenoura Subgroup; occurring together with Glyりｍａ･is (Gりｃｙｍｅｒitａ）ｊａｂｏｍｃａ
ＴＡＳＨＩＲ０，ｅtｃ‥（ＫＯＢＡＹＡＳＨｌ and AMANO, 1955).
ｏ Yadera, Shimo-Koshikiiima, Satsuma-gun, Kagoshima Prefecture; Member U-IIIa of the Upper Himenoura Subgroup; occurring together ｗｌtVv Ｌｉｍｏｂsiｓ ｆｅｏｇａtａ（ＩＣＨＩＫＡＷＡ and Maeda),ＢＴａｃｈｉｏｄｏｎｉｅｓ ７ｌａれ陥ｉ ICHIKAWA and Maeda, Apiotｒｉｇｏｎｉａ aff.ｐｏstｏｎｏｄｏｉａ Nakano,T＾ａｎｏｎａｖi％ ａｖｏａｎａｎｕｓ（ＩＣＨＩＫＡＷＡ and MAEDA), Glyりmeris (Gなりmerit a^ ｊａｐｏｎｉｃａ Tashiro, etc.. (Tasiro and NODA, 1973; TASHIRO, 1976).
ｏ Odegazaki, Fukami-machi, Ushibuka City, Kumamoto Prefecture; Member U-IIIa of the Upper Himenoura Subgroup; occurring together with “Ｃｒａｓsｏstｒｅａ”ｓχ）｡，Giｖｅ,ｙｍｅｒis （Ｇりｃｙｍｅｒitａ）ｌａｐｏｎｉｃａ Tashiro and Acila (Ｔｒtｉｎｃａｃtia）ｓhi-ｍｏｉtｍｅｎｓiｓTashiro. (this paper).
ｃ Asami, Fukami-machi, Ushibuka City, Kumamoto Prefecture: Member U-IIIa of the Upper Himenoura Subgroup; occurring together with Ｎａ？ｌｏｎｏｖｉｓａxｕａｉtａｎｕｓ（ＩＣＨＩＫＡＷＡ and Maeda), Gりりｍｅｒiｓ(Glycymeritα）ｊａｐｏｎｉｃａ Tashiro, etc.. (this paper).
It seems that the occurrencｆｔ oi ？＞tｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｊａｂｏｍｃａ ｊａｂｏｎｉｃａ（ＹＥＨＡＲＡ）･ is restricted exactly in Upper Campanian. Because,Ｓ ｂｈｅｎｏｃｅｒａｍｕｉsｃｈｍｉｄti(Michael), Ｓｂｈｅｎ.ｓａｃｈ ｢tｎｅｎsiｓ（ＳＣＨＭＩＤＴ），ａｎｄＳ♪ｈｅｎ，ｅｌｅｓａｎｕｓ ｂｓｅｕｄｏsｕｌｃａtｕｓ（ＮＡＧＡＯａｎｄ
1ろ8 Res. Rep. Kochi Univ･ ， Voi. 27., NatレSci.
- -on upper horizon than that of Ｓｂｈｅｎ. ｏｒｉｅｎはＵｓｏｒtｅれtaliｓ(SOKOLOW) zone. Also l will p d.j−
presumｅ， Ａｐｉｏtｒｉｇｏｎｉａ ｃｒａｓｉｏｒａｄｉａtａNakano,＾ａｎｏｒlavishｒｅｖｈ ICHIKAWA and maeda, and Ｍｉｃｒｏtｒｉｇｏれ１ａｉＴＯｕtｅｎｓiｓTashiro, are characteristic species in the Japanese Campanian stage. Since Member U-IIIa including Ｓtｅｉｍｎａｎｅｌｌａ（Ｙｅｈａｒella）ｉａｐｏｎｉｃａ ｏｂｓｏｌｅtａKOBA-YASHI and Amano, is upper than Member U-IIa ineluding.S. (7.)ｌａｐｏｎｉｃａｊａｐｏｎｉｃａ （ＹＥＨＡＲＡ）.Ｔｈｅ age of Member U-lIIa is not clear. l tentatively examine that the member
is able to include in Maestrichian, ０r Upper-most Campaniafi･’ according to our previous studies (Tashiro and NODA, 1973; ＴＡＳＨＩＲＯレ1976). ミ
Text-fig. 1. Map showing the fossil localities
A:Asami, F : Fukami, ０ : Odegazaki, S : Shimohira, Ｙ : Yamanoura,×:fossil localities
Description of species 。
’ Order Trigonioida Superfamily Trigonioida L八MARCK Family Trigoniidae Lamarck Subfamily Myophorellinae KOBAYASHI Genus ＳｉtｅｉｎｍａｎｅｌｌａCrickmay√1930 Subgenus ＹｅｈａｒｅｌｌａKOBAYASHI and Amano, 1955 Stｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella,）Ｔａｐｏｎｉｃａ=obｓｏｌｅは
KOBAYASHI and Amano
Plate l， Figs. 1-5･，Ｔｅχt-fig. 2-B
1955. Ｓtｅｉｎｍａｎｎｅｌｌａ（Ｙｐ.haｒella）ｊａｂｏｎｉｃａ var.≒obｓｏｌｅはKOBAYASHI and Amano, Japan Ｊｏｕｒ. Ｇｅｏｌ.Ｇ。fi-r., vol. 27, nos. 3-4, p. 202, pi". 14,‘figs. 4-5.
1916. Stｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）]ａｐｏｎｉｃａ ｏｈ％ｏｌｅtａ ＫＯＢＡＹＡＳ血 and ＡＭＡＮＯ： TASHIRO, Ｐ ｢ａｅｏｎt. Soc.ｉａｂａｎ，ｓｐｅｃ. Ｐａｐ.,no. 19, pp. 58÷59, pi. 7, figs. 18-21.
Ｍａtｅｒialｓ.- KSG. 2001 is a right external mould collected :at Odegazaki beach of Fukami-mach, Ushibuka City, Kumamoto Prefecture. KSG. 2002 is a internal mould of conjiointed valves from the same locality. KSG. 2003 is an : imperfect･ right‘ external moulds collected
On the occurrence ｏＩＳ￡ｅｉｎｍａｎｅｌｌａ（Ｙｆｈａｒｅｌｌａ） tｅａ obｓｏｌｅtａ （Ｍ.Ｔ.）_ 159
at the roadside exposure about 500 m west of Asami, Fukami-machi, Ushibuka City, Kumamoto Prefecture｡
Z:^ｅｃｒipiion.-Shell roundly triangular, moderately inflated; test rather thick; a littlelonger than high; anterior margin semicircular; vental margin broadly arched on anterior but nearly straight on posterior; siphonal margin weakly rounded. occupied about ａ thirds of valve length; posterior dorsal margin straight with about ａ thirds of valve length; umbo small, opisthogyrous, a little prominent, located at about ａ quarter from front of valve; escutcheon very narrow, lanceorated, strongly depressed from escutcheonal carina, ornamented by 3 0r more costellae; the costellae are narrower than their interspaces, extend horizontaly but subvertical against escutcheonal carina, from escutcheonal carina to dorsal margin, but not reach the dorsal margin; area moderately wide, occupied with fine but distinct growth lines except for near umbo; 3 0r more plain concentric or vertical constellae appear on the
umbonal region of the area; disk broad in nearly semicircular, ornamented by variable costae with about 11 in numbers, 3 0r less costae on umbonal region subconcentric or subhorizontal, generally plain, narrower than their interspaces, extended from marginalヽ carina toward umbonal anterior margin, but not reach the anterior margin; next 4 0r less costae diagonally extended from marginal Carina toward anterior margin, but soon bended to upwards on each midway, and became nearly horizontal on anterior marginal part; the costae finely tuberculated and narrower than their interspaces on the diagonally extended grade, but they gradually changing into broad and nodular costae on the horizontally extended grade; latter 4 0r so costae broader than their interspaces, bluntly and irregularly nodulated, stretched subradially from marginal carina toward nearly full distance of ventral margin; marginal carina somewhat angulated near umbo, but soon changing into bluntly elevated ridge on posterior; escutcheonal carina angulated. short with about a half length of marginal one: median groove very shallow, located partial to escutcheonal side: growth lines on the disk well developed on anterior and ventral marginal parts, very often cut across the noduled costae. formed irregularly waved lines｡
Ｍｅａｓｕｒｅｍｅｎts.−（ｉｎｍｍ.）
specimens
KSG. 2001, right external ｍＯＵ】d KSG. 2002, right internal mould KSG. 2003, left internal mould
Length - 63.1+ 55.0＋ 30.0+ Height 58.0 54.0 28.5+ Thickness - 12.0 − 6.0+
Ｒｅ-ｍａｒfeｓ.-Though Hayami (1975) suggested that this subspecies was a synonym of Ｓｔtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｊａｐｏｍｃａｌａｐｏｎｉｃａ（ＹＥＨＡＲＡ）.l regard that the subspecific or
more distinct difference
>eχists between ｏｈｓｏｌｅtａ･and ｊａｂｏｎｔｃａｓ． ｓｔて‥Ａ specimen was described aｓ ＴｒｉｇｏｎｉａｊａｂｏｎｉｃａΥEHARA from Oe mura, Higo Province (Oe of Amakusa-machi, Amakusa-gun, Kumamoto Prefecture) by Yehara C1923a, 1923b, 1931). The specimen was, however, considered as ａ variety ｏｉ Ｓtｅ伍ｍａれｎｅｌｌａ（Ｙｅｈａｒella) japoれｉｃａ （ＹＥＨＡＲＡ），bｙＫＯＢＡＹＡＳＨｌ and AMANO (1955). I think, the specimen from Oe of
Amakusa-machi, be able to classify tｏ Ｓtｅｉｎｍａｎぶａ（Ｙｅ.hnｒella）ｊａｂｏｎｉｃａｊａｂｏｎｉｃａ(Yehara), judging from its tuberculated carinae and median groove. This subspecies is discriminated from
140 Res. Rep. Kochi Univ., Vol. 27
１０ m m
-Tｅχt-fig. 2.
Ａ:Ｓtｅｉｍｎａｎｅｌｌａ（Ｙｅｈａｒella）ｉａｐｏｎｉｃａｊａｐｏｎｉｃａ(Yehara)
lateral and dorsal views, illustlating based 6n the specimens from the basal part of the Izumi Group at Himezuka of Dogo, Matsuyama City, Ehime Prefecture, and from Member Ｕ一Ha of the Upper Himenoura Subgroup at Fukkireura of Shimo-KoshikijimaにKagoshima Prefecture. Ｂ : Ｓtｅｉｎｍａｎｅｌｌａ(Yehａｒｅ.lla）ｊａｐｏｏｈｓｏｌｅtａKOBAYASHI｢ｃａ and Amano lateral and dorsal views of right valve.
Stｅｉｎｍａｎｅｌｌ（Ｙｅｈａｒella）1 ａｔｏｎｉｃａ ｊａｂｏｎｉｃａ(Yehara), in its smooth marginal and dorsal carinae and median groove which is not tuberculated, and also differs in its less numerous costae and costellae on the disk and escutcheon. more blunt but less numerous tuberculations or nodulations on each costa of the disk, and narrower escutchen about two thirds in length,
than those of S.（ｙ.）ｌａｂｏｍｃａ ｊａｂｏｎｉｃａ（ＹＥＨＡＲＡ）．ｌｎＳ．（ｙ．）ｊａｂｏｎｉｃａ ｊａｂｏｎｉｃａ(YEHA-RA), the costae on the disk are about 15 in numbers, the costellae on the escutcheon are about 8， the tuberculations on the carinae and the median groove are countable about 8 in numbers on each them, and ４ ０ｒ more umbonal costae on the disk are concentric. This subspecies is similat tｏ Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）himｕｒaiｓaniifeienｓiｓNakano (1958;
KOBA-YASHI and AMANO, 1955) from the basal sandstone of thelzumi Group in Kagawa Prefect-ure, in its features of costae on the disk, but differs in its less tuberculated carinae and median groove. S￡ｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｄｅｃｌzｅｉｎａ（ＫＵＢＯＴＡ）frｏｍthe Hakobuchi Group in Hokkaido (Nakano, 1958) differs from this subspecies in its terminaly located umbo.
POULTON (1977) classifiedStｅｉＴｉｍａｎｅｌｌａｔｏａ subgenus undｅＴ"Ｍｖｏｂｈｏｒella,l think, however, Ｓtｅｉｎｍａｎｅｌｌａ＼ｓa distinct genus under Myophorellinae. It seems that this subspecies probably
derived from Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｉａｂｏｎｉｃａｊａｂｏｎtｃａ,and showes one of representative
taxa which is able t0 leading Upper-most Campanian and IVIaestrichtian. And Ｓｉｌｅｉｎｍａｎｅｌｌａ （Ｙｅｈａｒella）ｊａｂｏｎtｃａｉａｐｏｎｉｃａ（ＹＥＨＡＲＡ）iSalso important∇trigonian which is restricted in
Upper Campanian｡
Occur・,zｃ。｡- Sandstone of Member U-IIIa of the Upper Himenoura Subgroup, at Odega-zaki beach of Fukami-machi, Ushibuka City, Kumamoto Prefecture; Sandstone of the same
On the occurrence of Ｓ^tｅｉｎｎｉａｎｅｌｌａ（Ｙｅｈａｒella） ohｓｎｌｅtａ (M.T. ) 141
member at the roadside exposure about 500 m west distance from Asami of Fukami-mach, Ushibuka City, Kumamoto Prefecture. Upper Hetonaian (Maestrichian and Upper-most
Campanian). GりｃｙｍｅＴｈ（Glｖｃｙｍｅｒiは）ｌａｂｏｎｉｃａTashiro,Ｎａｎｏｎａｍs ａｌむaiiaれｕｓ （ＩＣＨＩＫＡ-WA and Maeda) and Loエｏ ]ａt＞ｏｎｉｃａ(Amano) occur in those localities together with this subspecies.
Repository
The
specimens described in this paper are stored in the following two institutions, with
abbreviated indiscation by prefix.
ＫＥ: Faculty of Education,
Kumamoto
University .(Kumamoto
860).
ＫＳＧ:Institute of Geology, Faculty of Science, Kochi
University (Kochi,
780).
References
Cricmay, C. H. (1930) ; Fossils from Harison Lake･ Area, British Columbia. Ｃａｎａｄａ Ｄｅｉ＞t. ＭｉｎｅｓNat. Ｍｕｓ，Ｃｎｎａｄａ Ｈｕll.no. 63, Geol. Ser. no. 51, pp. 31-66, 23 pis.
Hatai, Ｎ. (1960) ; The Geology and the Geological structure of Amakusa･Shimo･Shima, Ｋｕ･ mamoto Prefecture. Set. Rep.ＫａｇｏｓｈｉｍａＵｎｉ-Ｄ.,no. 9, pp. 61-107.
Hayami, I. (1975) ; A systematic survey of the Mesozoic bivalvia from Japan. ＵＴＩtTJ.MitＳ., JJnii｝．Ｔｏｋｙｏ, Ｂｕll.no. 10, pp. 1-249, 10 pis.
KoBAYASHi, T. and Amano, M. (1955) ; On the Pseudoquadretae Trigonians,Ｓtｅｉｎｍａｎｅｌｌａ， in･the Indo-Pacific Province. Ｊ吋）ａｎＪｏｕｒ， Ｇｅｏｌ｡Ｇｅｏｇｒ.,vol. 26, nos. 3-4, pp. 193- 208, pis. 13-15.
Miki, T. (1975) ; Formation and Development of Sedimentary Basins during the Paleogene in Aniakusa and its Adjacent Areas, Western Kyushu.Ｍｅｍ. Fac.Ｓｅt.，Ｋ:ｙｕｓfiｕＵｎtil., Ｓｅｒ, Ｄ, ＧｅｏＬ.vol. 23, no. 2, pp. 165-209, p】s. 27-31.
and Uematsu,
M. (1973) ; The
Paleogene and Upper Cretaceous Formation in the
(1958J ; On Some Upper Cretaceous Ｓtｅｉｎｍａｎｎｅｌａ（Ｙｅｈａｒella）ｉｎJapan. Ｊ。ur. Sci,
(1927) ; On the surface ornamentation of the Pennatae Trigoniids, and on three New
(1976) ; Bivalve Faunas of the Cretaceous Himenoura Group in Kyushu、Ｐａｌａｅｏｉｉt South Part of Shimoshima, Amakusa Coal-field, with Special Emphasis on their Stratigraphic Relation and Ｐｅtｒographic Characters of Sandstones.Ｋ-Ｏｚａｎ Ｃｈｉｓhitｓｕ,vol. 23, pp. 227- 236.
Nakano, M. (1957) ; On the Cretaceous pennatae trigonians in Japan. Ｊａｐａｎ，Ｊｏttｒ. Ｇｅｏｌ. ＧＥ。ST., vol. 28, nos. 1-3, pp. 107-120, pis. 8-9.
HiｒｏｓｈｉｍａＵｎｉ。。Ｓｅｒ. C, vol. 2, no. 2, pp. 83-88, pis. 13-14.
Nod人, M. and Ｔ人Ｓ町RO, M. (1973) ; The fauna from Dogo-Himezuka, Matsuyama City and its stratigraphic significance. Japan. Ｊｏｕｒ，Ｇ。ol.,vol. 79, no. 7, pp. 493-495.
POULTON, T. P. (1977) ; Early Cretaceous Trigoniid bivalves of Manning Provincial Park, Southwestern British Columbia. Ｇｅｏｌ. Ｓｕｒ・｡ Ｑａｎａｄａ.Ｐ＾ｉＰ. ７Ｓ−タ，25 PP-, 3 pis.
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Species of the Trigoniids from the Himenoura Group, Kyushu, Japan. TΓα。i.Proc. Ｐ ｢ａｅｏｎt，Ｓｏｃ．Ｊａｐａｎ, Ｎ. Ｓ.,no. 86, pp. 325-339, pis. 40-41.
142
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and NODA,
M. (1973) ; The
Geological Age
of the‘'Himenoura
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Japan.ＪｏＵＴ･，Ｇｅｏｌ．Ｓ。ε．Ｊａｐａｎvol.79， no. 7, pp. 465-480, pi. 1.
Yehara, S. (1923a') ; Cretaceous Trigoniae from. Amakusa island, Prov. Higo, Kyushu, Japan. Ｊｏｕｒ.Ｇｅｏｌ.Ｓｏｃ. Tofeｖｏ,vol. 30, no. 352, pp. 35-44,･pls･｡11-12.
(1923d) ; Cretaceous trigoniae from southwest Japaｔl. Ｊａｐａｎ.Ｊｏｕｒ、Ｇｅｏｌ.Ｇ。ｇｒ.、
(1931) ; Trigoniae from Japan. Iiｖａｎａｍｉ･Ｌｅｃはｒｅ Ｓｅｌｉｅｓ. Ｇｅｏｌ. Ｐａｌａｅｏｎt. pp. 3-25
Japanese
writing for place l!antes
Amakusa-gun
Amakusa-Shitnojima
Aonai
Asami
Dogo
Fukatni
Fukkireura
Higo
Hitnezuka
Imuta
Kitadani
Koshikijima
Matuyama
Miyanokawachi
郡島内海後海浦後塚田谷島山
告 よ？! 牟
天天骨浅道深吹肥姫閥北甑松
宮野河内Odegazaki
Oe ｌ
Oemura ’
Onsen-gun
‘Oshima
Sanuki .
Satsuma･gun
Shimohira
Shimokoshiki
Taira。
Ushibuka
Yadera
Yamanoura
Ｙリyama
オデガ崎大大温大讃薩下下平牛家山湯
江泉 摩 ノ
江村郡島岐郡平甑良深寺浦山
(Mannscript
received September
29，1978)
(Published
Marcホ30,
1979)
｀ぷ’−．
ゝ ノ １ １ １ ど lj l ゝ １ ； ｌ ・ １ １ 。 ･ Ｉ ‥ ‥ ‥ ‥ り １ - ･ ｔ ･ ｉ Ｊ． ｄ ・ １ 。 ゛ 、 ・ ’ ・ ｊ Ｊ ､ ・ １ １ 、 ' I . ' 、 ４ｊ l ゛ l j . . ゜ ｀ ’ Z ° ゜ ● Ｊ Ｉ P L A T E Ｉ . ， . J ’ ， ‥ I ･ ･ . ’ ， . j Ｉ ● Ｆ ， Ｉ ¶ ９ ｊ ｉ ヽ ; ． ４ ， ･ １ ・ｉ
リ
ｌ
・．１ ハ 丿 ・ ４ Ｑ べ Ｓ ｊExplanation of Plate
Stｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｊａｐｏｎｉｃａｏｂｓol・tａ.ＫＯＢＡＹＡＳ田andAmano
Fig. 1 : Lateral view of right valve. rubber cast of KSG 2001, ×1, Loc. Odegazaki of Fukami-machi, Ushibuka City, Kumamoto Prefecture. I Fig. 2 : Dorsal view of same specimen, rubber cast,×1.
Fig. 3 : External mould of same specimen,×1.
Fig. 4 : Internal mould of con jointed "valves, KSG. 2002, showing the right side,×1, Loc. ditto.
Fig. 5 : Lateral view of imperfect right valve, rubber cast of KSG. 2003,×1, Loc. Asami, Fukami-machi, Ushibuka City, Kumamoto Prefecture.
Ｓtｅｉｎｍａｎｅｌｌａ（Ｙｅｈａｒella）ｊａｐａｎｉｃａｉａｐｏｎｉｃａ（ＹＥＨＡＲＡ） (for comparison)
Fig. 6 : Umbonal view of right valve, rubber cast of KE 2136.×,1， .， Loc. Oshima islet, Ushibuka City, Kumamoto Prefecture.
Fig. 7 : Lateral view of right valve, plaster cast of KE 2135, XI, Loc. y Himezuka of Dogo, Matsuyama City, Ehime Prefecture.
