九州大学学術情報リポジトリ
Kyushu University Institutional Repository
Pelecypod Fauna of the Shimajiri Group in Miyako-jima, Okinawa Prefecture, Japan
Sato, Yoshio
Faculty of Sciences, Kyushu University
Masuda, Koichiro
Department of Geology, Miyagi University of Education
Shuto, Tsugio
Kyushu University : Emeritus Professor
https://doi.org/10.5109/1526112
出版情報：九州大學理學部紀要 : Series D, Geology. 26 (1), pp.1-49, 1986-01-20. 九州大学理学部 バージョン：
権利関係：
Mem． Fac． Sci．， Kyushu Univ．， Ser． D， Geo1．， Vo1． XXVI， No．1，
pp．1−49， text−6gs．1−2， table 1， plates 1−5， January 20，1986
Pelecypod Fauna of the Shimajiri Group in Miyako・lima， Okinawa Prefecture， Japan Yoshio SATo， K△ichir6 MAsuDA＊and Tsugio SHUTo＊＊
Abstract
The present paper is the first report on the paleontological study of the molluscan fauna（Pelecypoda）from the Shimajiri Group in Miyak《＞jima and is divided into two parts． Outline of the geology of Miyako−jima， strati−
graphical position of fossil localities， occurrence of fossils and correlation of the molluscan fauna are included in the first part． Systematic description of the fauna is to be given in the second part． The molluscan fauna from the Shimajiri Group in Miyako−jima is correlated with those of the Shimajiri Group in Okinawa−jima， the Miyazaki Group and the Kakegawa Group in Soutllwest Japan， Fifty−three species are described and 3 species and l sub−
species are new to science．
Introduction
The Shimajiri Group developed in Miyako−jima of the Ryukyu Islands，
Southwest Japan， has been stratigraphically studied by DoAN， PAsEuR and FOsBERG（1960）， UJIIE and OKI（1974）， NAKAGAwA， NIITsuMA， MuRAKAMI and
WATANABE（1976）， YAzAKI（1978）， YAzAKI and OYAMA（1979，1980）， and
NAKAMoRI（1982）． While the geological age of that group has hitherto been assigned to the Late Miocene to Pleistocene based upon planktonic foraminifersby HuANG （1968）and UJIIE and OKI（1974）， and based upon calcareous
nannoplanktons by NIsHmA（1973）， it has been considered to be Pliocene in age based upon planktonic foraminifers and paleomagnetism together by KAME−YAMA（1975）and NAKAGAwA， NIITsuMA， MuRAI（AMI and WATANABE（1976）． As
pointed in OGAsAwARA alld MAsuDA（1983）， nothing has been done on molluscs．The present writers collected加merous fossil molluscs from the Shimajiri Group at several localities in Miyako−jima． Examination of those molluscs gives
interesting knowledge on the faunal relation with the Kakegawa fauna of
Southwest Japan． The present paper deals with the pelecypods and the result of gastropods and a few scaphopods will be publi8hed at later date．＊ Department of Geology， Miyagi University of Education．
＊＊Emeritus Professor of Kyushu University．
Manuscript received August 10，1985．
2 Y．SATo， K． MAsuDA， and T． SHuTo
Part l Stratigraphy and Pelecypod Fauna
Outline of the Stratigraphy
The Shimajiri Group mainly cropping out along the northeastern coast of Miyako−jima is classified into the following formations in upward sequence
（NAKAMORI，1982）．
Oura Formation：−This formation corresponds with the Ikema Sandstone and the Ogami Sandstone of DoAN， PAsEuR and FosBERG（1960）， the Nanseien Formation of UJIIE and OKI（1974）and the Ogami−jima Formation of YAzAKI
（1978）and YAzAKI and OYAMA （1979）．
The lower part of this formation consisting of conglomerate and cross−
bedded sandstone crops out in the Ogami−jima． The upper part consi8ting of sandstone and alternation of sandstone and silt80ne is distributed at nortll of Shimajiri and its environs in Miyako−jima． Molluscall shells are found from Ogami−jima（Locality 1）and nortll of Shimajiri（L、ocality 2）．
Oonogoshi Flormation：−This formation consists of massive sil七stone and corresponds with a part of the Gusukube Shale of DoAN， PAsEuR and FosBERG
（1960），the lower part of Yonahama Mud8tone of UJIIE and OKI（1974）and the Iower part of the Gusukube Formatioll of YAzAKI（1978）and YAzAKI and
OYAMA（1980）． Many molluscan shells are collected from northwest of Pise−
ogazaki（Locality 3）alld Piseogazaki（Locality 4）．
Yonahama Formation：−The Nobaru Formation of DoAN， PAsEuR and
FosBERG（1960）， the upper part of the Yonahama Mudstone of UJIIE and OKI（1974），and the upper part of the Gusukube Formation， Higa conglomerate of
YAzAKI（1978）and YAzAKI and OYAMA（1980）correspond with this formation
℃onsisting of tuffaceous siltstone， tuff and conglomerate． Numerous fossil molluscs are collected from the conglomerate developed at northeast of Higa，
Gusukube−cho（Locality 5）．
Minebari Formation：−This formation corresponds with the upper part of the Gusukube Formation of DoAN， PAsEuR and FlosBERG（1960）， the Minebari alternation of UJIIE and OKI（1974）and the Henna Formation of YAzAKI（1978）
and YAzAKI and OYAMA （1980）， and consists of alternation of sandstone and siltstone． Some fossil molluscs llave beell recorded（NAKAMoRI，1982）， but the writers did not collect any molluscs．
Occurrence of fossils and remarks on Fossil Fauna
The results of field ob8ervation are l）rieHy described in the following lines．
Fossil localities are five and their Iocations are shown in Fig．1． Precise de−
scriptions of fossil localities are Iisted in the separate cllapter．
ユ） Locality 1：−Ogami−jima（Oura Forma七ion）．
Some molluscan shells occur in conglomeratic cross−bedded sandstone and siltstone which are irregularly ill association with thill lignite seams． The re一
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 3
D
4
Amami islS．
工
…雲・。諸。、a
Miyako isls．
・㌘・・
㌃艶・入r1
書a im㌔、。m、rm。／ ＿＿
Ka了imata
Miyako−lima
Fukusato
Fig．1． Map showing the fossil Iocalities of the Shimajiri Group in Miyak（トjima．
presentative species is Cγα8808Zγθα 9 9α8 （THuNBERG）． The association of O夕α8808かθαg⑳α8，Cy6Z仇αsp． cf．（0．8仇θη8Z8 （GMEロN））and 7θ1θ860p玩〃2 sp．
suggests that a brackish environment existed during deposition in the Ogami−
」1ma area・
2） L・ocality 2：−Shimajiri（Oura Formation）．
Mo11uscan shells occur sporadically and are orientated nearly parallel with bedding planes in the well sorted very 6ne sandstone in association with simple corals and rarely with echinoids． The representative species are A仇μ8乞μ働 plθ％グα〃θ6亡θ801ヒ仇αωαθ犯8Z8 n． subsp． which occurs as conjointed valves and i8 accompanied by small isolated shells of C〃Zα仇び8（1∬伽α6ん1α仇γ8）8α￠oi（YoKo−
YAMA）．
3） Locality 3：−Northwest of Piseoganzaki（Oonogoshi Formation）．
Molluscan shells consisting of isolated and somewhat fragmental pelecypods are densely crowded in lenticular medium−grained sandstone intercalated in silt−
stone． Among the molluscs Cん1α伽〃8（ハ4『伽↓αoん1α？砲8）8αεoτandメ4ηo仇乞αcん仇θη868 PHIL、IPPI are the representative sp㏄ies．
4） Locality 4：−Piseoganzaki（Oonogoshi Formation）．
Molluscs occur sporadically and are orientated nearly parallel with bedding plane in the siltstone． Small shells of A伽援W仇μθμγoηθ6εθ80ん仇αωαθη8Z8 n．
subsp． andα〃6〃物θγZ8γoZ耽∂α（DuNKER）are the representative species from this locality． They usually occur as conjoined valves．
N3
Loc．2
NoN3
Loc．3
N1（6）
／B
NoN3
Loc．4
N1｛6）
NON3
Loc．5
N1（25）
Specific name
Loc．2 Loc．3
Loc．4Loc．5
1．毎Z・d加ぬα亡・（HINDS｝
2． αωαゼαrθα鋤αθ・・ゼθ（YOKOYAMA｝
3．4ηαゴαrα rs6αρカαrσαノ ηodαz， n． sp．
4．Aηα（涕αrα rSoαρゐαアoαノ8㍑z欧坑 （YOKOYAMA）
5．4ηα〈7αアα r30αρゐαroαノ 亡rτρθηz已08τα （NYsrr）
6．況rZαreαη￡ンα震oゴ仇7αθη8掬， n． sp・
7σZy・抑♂S r・鋤dα（DUNKER）
8．A〃川89ゼ況m p乙ε㍑poηθ06θs o万ηαωαθηsτ3， n． subsp．
9．4mμ88foρθ性θηρrαεsゼ9ηゼs （YOKOYAMA）
O．cλ乙αmンs r τmαoハ1ταノηン3／ s（2亡oτ （YOKOYAMA）
1．M・9αeαr碗ασPα・況Zτ・・s亡α亡α（NαωRA｝
2．PαP厄α・f．αm・尻乙￡・（PI｛1LIPPI）
aOZ・願亡乞・P・ρン…θ・（GRAY）
Fig．2． Vertieal distribution of the living representatives of the pelecypod species and stratigraphical ranges of important index fossils． Each fossil loeality is arranged in ascending order． Parenthesized figures are the total number of species．
No
ら
■
ω卜弓O︑︼⁝︵°旨缶ωdO﹄w9田合弓sOO出d弓O
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 5 5） Locality 5：−Higa（Yonahama Formation）．
Molluscs comprising many water worn shells are denselyρrowded in the andesitic pebbly conglomerate． Among themα〃￠〃批θγ乞8γoε耽∂αis the most representative species．
Recent species from the Shimajiri Group on Miyako−jima is 26 alld 65 per−
cent of the total number of species． As shown in Fig．2， living representatives of the pelecypod species from the Shimajiri Group in Miyako−jima are generally living in a depth zone from tidal No to mesoneritic N2（between 20−30 and 50−60m）in their vertical distribution． CんZα？η〃8（ハ4伽α￠λ1αれび8）8αεoτ（YOKO−
YAMA）and A仇μ88ioPθ6εθπPγαθ8ig励8（YOKoYAMA）found at Loc．2七〇Loc．5 are the important indices for the Pliocene in South Japan．
Correlation and Geological Age
The complete faunal list is presellted in Table 1． Fifty−three species were distinguished among the molluscs obtained from the Oura， Oonogoshi and Yona−
hama Formations and among them 3 species and l subspecies are found to be new to science． CんZα仇〃8（M伽αc川α？吻8）8α加Z（YoKoYAMA）ranging from the Oura Formation to Yonahama Flormation in the Miyako−jima is stratigraphically very important species and also A％α肋γα8θ肋ηθη8ゼ8（MARTIN），Aηα∂αγα8殿μ磁
（YoKoYAMA）， z1？ημ88τoタθ6τθ％Pγαθ869励8 （YoKoYAMA）， etc． are also regarded as stratigraphical indices． As they have been㎞own only from the Pliocene formations in the southern Japanese Islands and Taiwan， it is evident that the geological age of the Shimajiri Group is Early Pliocene in a twofold classi6−
cation． On the basis of faunal assemblages the Shimajiri Group in Miyako−jima is reasonably correlated with the upper part of the Shimajiri Group in Okinawa−
jima， Tajima Formation in Tanega−shima， Kagoshima Prefecture， the Miyazaki Group in Miyazaki Prefecture， the Tonohama Group in Kochi Prefecture， the
Kakegawa Group in Shizuoka Prefecture and the Byoritsu Formation in
Taiwan．Depository of specimens
All the specimens described in the present paper are preserved and re−
gistered in the Department of Geology， Faculty of Science， Kyushu University．
List of fossil localities
Loc．1 （Ogami−jima）：−Sea cliff， about 100 m ea8t of Ogami， Hirara City，
Ogami−jima， Okinawa Prefecture． Oura Formation（Long．125°22 12 E， Lat．
24°59 11 N）．
Loc．2（Shimajiri）：−Sea cliff， about 200 m north of Shimajiri，且irara City，
Miyako−jima， Okinawa Prefecture． Oura Formation （Long．125°23 12 E，
Lat．24°52 23 N）．
Loc．3 （Northwest of Piseoganzaki）：−Sea cliff， northwest of Piseoganzaki，
about l km northeast of Fukuyama， Hirara City， Miyako−jima， Okinawa
6 Y．SATo， K． MAsuDA．， and T． SHuTo
Table 1． List of fossil pelecypods from the Shimajiri Group in MiyakΦjima．
Specific Name
∠4cτ1α（∠4 c元Zα）∂狗α冗cα￠α（HINDS）
1VμcμZαηα（欠んθ8励θdα）sp．
∠4￠αγsp．
Cαγ掘πθiZo￠αγ掘∫θγα（HABE）
17αωαづαγ￠αμωαθη8ぜ8（YOKOYAMA）
ノ1？τα《1αγα（欠08αγ￠α）Sθdαηθ？τ8i8（MARTIN）
A物αdαγα（S￠αPんαγ￠α）ηodαちn． sp．
∠4ηαdαγα（S￠αpλαγcα）8視zμMi（YOKOYAMA）
∠4ηαdαγα（8cαP九αγ￠α）￠γi6θ励co8￠α（NYST）
S￡γ伽cα励〃αb∫加αθη8i8， n． sp．
∠4ゲcOP8i88〃仇仇θ休icα（REEVE）
CμcμIZαθαργαημZo8αJONAS GZ〃c〃仇θが8γo￠μπ（1α（DUNKER）
Tμθθ￡oηαんαηzα初αi（NoMuRA and ZINBo）
1》fo（況oIμ8 sp．
A仇μW御p』γoηθ￠εθ80ん仇αωαθη8つ8，n． subsp．
A？ημ88iopθc￠θηpγαθ8ig励8（YOKOYAMA）
α↓Zα？吻8（ハぜ伽α￠λzα伽〃8）8α￠oi（YOKOYAMA）
Co㎜μopαII飢伽sp． cf． C． 拠θη8i8（NoMuRA and NIINo）
GloγipαII飢1れpαZI伽仇（LINNAEus）
．4耽α6ん1α仇〃8sp．
C7〃P鋤θθ￡θηMo58θ㎜α￠θπ8元8（OYAMA）
P倫α￠μZαsp．
4ηomiα6んi礼θηsi8 PHILIPPI O8￠γθαdθη8θZ砺れθIZo8α1」ISCHKE Cγα8808￠7°θαgiρα8（THUNBERG）
Cλα？拠グαpoM￠αLA．MARCK
C〃6Zocαγdiαsp． cf． C．∫θγγμ9仇θα（CLEssIN）
元fθ9α6αゲd α9γαημli￠08￡α施（NOMURA）
Bα￠ん〃施γ仇μ8∫ouθoIα施8（SOWERBY）
γθP励αrd飢仇sp．
17α8碗￠αγd《2L？ηsp．
Fμ励αsp．
丑fα6鋤αsp．
P8α仇γηo加θ￠α（P8θ2L（107ηθ￠i8）PγαθγμP毒α（SALIsBuRY）
ISoZθc耽仇8仇勿α〃oグ乞仇αθ砲8， n． sp．
A20パ？蹴8αbbγθ砂乞α勧8（GOULD）
刀ぜθio￠αγdiα μlgα冗s（REEVE）
γθ蹴8（γθ励パcolo掘θα）∫o θoIαεαSOWERBY γθ7協8（γθη￡γi￠oIαγiα）施γθμ祝α（GOULD）
GZ〃￠〆o励α2 sp．
Ciγ￠θsp．
Lio60η￠んα（S視16伍ocoη6λα）Pんi吻P仇α九仇（HANLEY）
1）08仇iα（Pαγ（lo8仇iα）α㎜Pんゼ（1θ8仇oi（元θ8（REEVE）
Do8掘αsp．
PαPんiα（PαPんiα）θ励1τ8SHUTO 刀1θγθ￠γ伽sp． cf．ハぜ．九80γiα（RODING）
Cy￠Z仇αsp． cf． C．8i？τθη8乞8（GMELIN）
CZθ仇θ？τ￠iαpαp〃γα￠θα（GRAY）
∠4励so60γb刎α加8αηα（YOKOYAMA）
∠4？zi80￠0γb刎α806乞αli8（MARTIN）
λf〃αdoγα沈θbθ乞HABE Cαπlio？η〃αsp．
Locality 1 2
314｝5
C
R
RFR
C＊
R
C R
FA
C
CF
F
FCFFR
F C
RA
R R R
A
CF
R
CR
F
F R R
FF
C
A
R
R R R
RCRR
R A C
A CRRRCRRF
C
A RR
R
CARRF CCF
＊Abbreviation：A−Abundant；C−Common；F−Few；R−Rare．
Pelecypod Fauna of the Shimajiri Group in Miyako−jima
7
Prefecture． Oonogoshi Formation（Long．125°24 7 E， Lat．24°48 N）．1」oc．4 （Piseoganzaki）：−Sea cliff at Piseoganzaki， about 1．5 km east of Fuku−
yama， Hirara City， Miyako−jima Okinawa Prefecture． Oonogoshi Formation （Llong．125°21，11 E， Lat．24°49，4 N）．
Loc．5（｝Iiga）：−Sea cliff， about 2 km northeast of Higa， Gusukube−cho， Miya−
ko−jima， Okinawa Prefecture． Yonahama Flormation （Long．125°23 21 E，
Lat．24°46 52 N）．
References cited（geology and biostratigraphy）
DoAN， D． B．， PAsEuR， J． E． and FosBERG， F． R．（1960）： ］Military Geology of the Miyako archipelago， Ryukyu Retto（translated into Japanese by SuzuKI， K．，1973，σθo−
Zoθ 6αZ Z）α￠αo∫OMηα初αP夕θ∫θ￠ωγθ），1，35−83．
HANzAwA， S．（1935）： Topography and Geology of the Riukiu Islands．＆元． Rθp．，
Toん01Cμ 1？ηρ． 乙γγμrり．， ［2］， 1「7， 1−61．
HuANG， T．（1968）：Smaller Foraminifera from Miyako−jima， Ryukyu． Sci． Rθp．， roんo〃μ
σητrtノ．，［2］，4④，47−−63．
KAMEYAMA， T．（1975）： Smaller Foraminiferas from Ogami−jima Ryukyu Islands．
Eαπん8《ガeπ￠θ（Joμゲ．0∫￠んθA88促．∫0γ伽Gθol． Coμ．仇」αPαη， CM吻砿α9α〃川，
29， （6），275−297．
NAKAGAwA， H．， NIITsuMA， N．， MuRAKAMI， M． and WATANABE， T．（1976）：Preliminary report of Magnetostratigraphy of the Shimajiri Group in Miyako−jima and Kume−
jima（in Japanese）． GθoZoρ《cαZ 8ε泌τθ80∫￠んθR抑吻μ181α城8，1，55−64．
NAKAMoRI， T．（1982）： Geology of Miyako Gunto， Ryukyu Islands， Japan（in Japanese with English abstract）． Cσ励γ．1η8￠． GθoZ． PαZθoηち㌘oλoWσ励ψ．，（84），23−39．
NIsHIDA， S．（1973）：Preliminary study of the Upper Cenozoic calcareous nannoplankton assemblages from the Nansei Islands（in Japanese with English abstract）． Mθη．
GθoI． So6．」αpαγτ， （8），65−75， pls．1−2．
OGAsAwARA， K． and MAsuDA， K．（1983）： Notes on tlle Paleoenvironments based upon the Cenozoic molluscs in the Ryukyu Islands（in Japanese with English abstract）．
1∬θγη．σθoZ．800．」αpαγ2， （22），95−105．
UJIIE，且． and OKI， K．（1974）： Uppermost Miocene−Lower Pleistocene， Planktonic Foraminifera from Shimajiri Group of Miyakojima．1Lfθ初．2Vα￠η． S6τ．1吻8．，（7），
31−52．
YAzAKI， K．（1978）： About the Shimajiri Group of MiyakΦjima， Ryukyu Islands（in Japanese with English abstract）．σeoZo9τoαZ 8￠履iθ80∫R騨吻μ18Zα励8，（3），
81−88．
and OYAMA， K．（1979）： Geology of the Miyakojima−Hokubu District． Qαγ∂一 γαηg・1θSθ碗θ8SCα1θ1：50000，1匪汐αbji働α（ill JapaneSe With EngliSh abStraCt），
19， （3），1−43．
， （1980）： Geology of Miyakojima District．乃i｛1．，19，（4），41−83．
Appendix
Alphabetical index of place names with Japanese writing．
1．Fukuyama（福山）
4．Minebari（嶺原）
7．Nanseien（南静園）
10．Oura（大浦）
12．Shimajiri（島尻）
2．Gusukube（城辺） 3． Higa（比嘉）
5．Hirara（平良） 6． Ikema−jima（池間島）
8．6gami−jima（大神島），g．60nogoshi（大野越）
11．Piseoganzaki（平瀬尾願崎）
13．Yonahama（与那浜）
8 Y．SATo． K． MAsuDA， and T． SHuTo
Part 2 Systematic description
K6ichir6 MASUDA， Yoshio SATO and Tsugio SHUTO
Family Nuculidae
Genus A6乞1αH． and A． ADAMs，1858
Ac江α （Ac 1α） ∂初αがcα￠α （HINDS，1843）
P1．1， Figs．1，2 1860．
1920．
1936．
1954．
1958．
1959．
1965．
1966．
1973．
1977．
1980．
2VμcμZαd初αη￠α￡αHINDs． HANLEY in SowERBY， Tみ杉8． Coη￠ん．， voL 3， p．155，
pl．230，6g．151．
2Vμ側1αγη后α6τ施ADAMs and REEvE． YoKoHAMA， Joμγ． CoZZ． S￠i．，1祝P．
σγμ〃．To〃〃o， vo1．39， art．6， P．180， pL 19，6gs．9a−c．
Acilα（Acτ1α）d初α冗αL￡α． SCHENCK， G￠oL So￠． A祐θ〈r．， Spθc・PαP杉γ， no・4，
p．90，p1．15， figs．1−10， textpfigs．8 （1，2）．
∠4c祝α∂初α冗θα加 ． TAKI and OYAMA， PαZαθo励． S促．」αPα舵， SPθ￠・PαPeγ，
no．2， pl．20，血gs．9a−c．
ノ1ciZαd劫αγi￠α￠α． HABE， PμbZ． Sθ診01レfαγ． BづoI． Lαb．， voL 6， no．3， P．243，
pl．12， fig．8．
A￠祝α（∠4￠τZα）｛1初α夕iαLω．IWAI， B祝II． Fα￠． Edμ￠．， Hか08α腕σ励仇， no．5，
p．53，p1．2，6g．13．
ノ1￠侃αd初αγi6α如． KASENO and MATSUURA， S6i．、RθP．， Kαπαzα初α Uη初．，
vol．10， no．1， pl．7，6g．8．
Ac元1α｛1初αγicα￠α． SAKAGAMI e毒α1．， Jo耽． Hoんんα滅oσ励 ． Ed鵬．， SeT． B，
vo1．17， no．1， p1．2， fig．14．
ノ1￠i乙α （∠1￠izα） ￠Z初㎝［oα￠α． OYA】班A， PαZαθoη￠． Soc． 」αPα7τ， Sρθ6． Pαρ●γ，
no．17， p．75， p1．20，6g．25．
ノ16祝α （≠1c∂α）〔1初αγゼ￠α仇． HABE， Sy8ε．ハぜoZZ．」αpαη， p．15， p1．2， fig．5．
∠4c祝α（Ac視α）d初αが￠OIεα． NODA， S（元． RθP．1πsτ． Gθ08￠i．， Uπ励．欠8砿視bα，
vol．1， p．65， pl．1，6gs．5，10a−b．
Rθ糀αγん8：−The present specimens are characterized by their medium−
sized， moderately inflated shell with rostral sillus， distinct divaricate sculpture on surface， prominent teeth， anteriorly protruded deep resilifer and負ne marginal serration and identical to A￠ぜ1α （A￠￠〜α） 〔ガ勿αグZcα￠α （且INDs）．
A￠ilα8μb働γαbZI 8 MAKIYAMA （1926）described from the Miocene Hei−
rokudo Formation in North I（orea resembles the present species， but 8秘b励γαb砺8 can be distinguished from the presen七〇ne by i七s very small escutcheon， rounded anterior margin and smaller number of anterior teeth．
The present species has been illustrated from the Miocene formations in
Central to Northern Japan（AoKI，1954；ARAKI，1960；TANAKA，1960；MAsuDA
and TAKEGAwA，1965；IwAI，1965）， but as the Miocene specimens are usually ullfavorably preserved， further detailed study of them is necessary to settle this problem．DZ仇θぴioη8（in mm）：一
Valve Height Length Depth
Intact
18．4 24．5 13．7
Intact
18．0 23．3 11．8
Intact 15．0 19．6 10．7
Right
15．5 21．0 6．0
Left
18．0 23．2 6．9
Left
15．2 20．0 5．8
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 9 Oo6μηθη￠θ：−Loc．2（Common器）；Loc．5（Rare普）．
GθoZog 6砺8￠γ乞b励τoη：−Nojima Formation， Kanagawa Prefecture；Higashi−
meya Flormation， Aomori Prefecture；Omma Formation， Ishikawa Prefecture；
Tomikawa Formation， Hokkaido；Shinzato Formation， Okinawa Prefecture．
Rθ￠θ励（IZ8εγ乞bμ万oη：−Honshu， Shikoku， Kyushu， Japan Sea and East Chi−
na sea．
GθologZ￠ゲαη9θ：−Pliocene to Recent．
Family Malletiidae
Genus Oαγ仇仇θτZo KuRoDA and HABE，1971
Cαがγ冗7τθ祝0 6α冗ηガθγα （且ABE，1951）
Pl．1， Fig．3
1951．
1971．
Mα〜〜θεゼα（2VθτZo）oαγτ？2げθγαHABE． Gθη．」αραη． SλθZZ8， no．1， p．22，6gs．
16，17．
cα噺飢θ伽6α吻ザθγα．
p．505，pl．66，負g．2．
KuRoDA， HABE and OYAMA， SθαSれZZ8 Sα9α阻i Bαy，
Rθ仇α袖8：−One rather well preserved specimen was examined． Shell small in size， thin， elliptical， slightly inflated；surface smooth but with rather distinct concelltric growth lines near ventra】margin and with two rather distinct carinae running from beak to posterior and anterior corners．
1）物杉η8 o犯8（in mm）：−Height 7．5， length 10．0， depth ca．3．0．
Oowゲγθ？τ￠θ：−Loc．4 （Rare）．
Rθ6θ励臨￡γ訪μ励η：−Honshu（Boso Peninsula as north limit）and Shikoku．
GθoZogZ6γαηgrθ：−Pliocene to Recent．
Family Nuculanidae Genus 2VμのzlαηαLINK，1807 Subgenus Tんθ8勿ZαZα IREDALE，1929
1Vμ6μ1α72α （Tんθ8￠2／1θ（Zα） sp．
Pl．1， Fig．4
Rθ祝α袖8：−One imperfect specimen was examined． The present taxodont specimen is characterized by its two ridges running from beak to posterior corner and somewhat lamellated coarse concentric cords on surface and is rea−
sonably included in Tんθ8ε〃1θ∂α． Further comparison can not be done because of imperfect preservation．
D伽θη8τoη8（in mm）：−1｛eight 6．5， length 12．0， depth ca．3．5．
0￠￠μゲγθ？τ￠θ：−Loc．4（Rare）．
＊Abundant：more than ten specimens， Common：more than血ve specimens， Few：more than two specimens， Rare：only one specimen．
10 Y．SATo， K． MAsuDA， and T． SHuTo
Family Arcidae
Genus AoαγGRAY，1857
A￠αγsp．
．Rθγηαγ〃8：−OIle fragmental specimen was examined． Shell small in size and with distinct network by distinct radial七hreads and concentric growth lines．
0￠6％γγθ？zcθ：−Loc．5（Rare）．
Genus 17αωαづαゲ￠αDALL， BARTscH and REHDER，1938 Hαψαταγ6α％ωαθη8i8 （YOKOYAMA，1928）
P1．1， Fig．5
1928．
1935．
1958．
1959．
∠4γcαμωαθη8τ8YoKoYAMA． Joμγ． Fα￠． Scτ．，1γηP．ση初．7 o〃〃o， Ser．2，
vo1．2， pt．7， P．349， P1．67， figs．13，14．
βα￠ん〃αroα，，μ初αθπ8τ8． OTUKA， B2Lμ．」匿αグ仇q．1eθs．乃28￠．， ro〃〃01祐P．τ乃τ加り vo1．13， pt．4， p．884， p1．55， figs．114，115．
1irα初α夜zγ6α ZLり〃αθη8τ8．
p．254，p1．11， fig．10．
17αωαδα7αL μωαθη8i8．
HABE， PμbZ． Sθ杉0 1Lfαγ． BioI． Lαb．， vo1．6， no．3，
MAKIYAMA， PαZαθ0励．80￠．」αpαη， Spθ6． Pαpθγ，
no．5， p1．65，6gs．13，14．
1966． Hα脚α伍γcα％初αe7τ8伝． NoDA， S￠i．1eθP．， Toんoんμ σηi仇，2nd Ser．， vo1．38，
no．1， p．75， pl．10， fig．8．
1971． 17αωα伽r6αμωαθπ8Z8． KURoDA， HABE and OYAMA， SθαSλθZZ8 Sαρα仇 Bα〃，
p．519，p1．67，6gs．3，4．
1980．Hα2〃α加γcα％初α仇8 8． NoDA， S6i． Rθp．1η8￠． Gθoscτ．，ση初．欠8励μbα， vo1．1，
p．72，p1．1， figs．19a−b，20．
Rθ仇α袖8：−OIle well preserved specimen was examined． The present speci−
men is characterized by its small， elongated quadrate shell with median depres−
sion and about 27 radial ribs which are somewhat granulate， broader than their interspaces and sometimes divide into two parts by a shallow longitudinal fur−
row near ventral margin． It quite conforms with Hα初α5αγ6α％初αθπ8Z8（YoKO−
YAMA）．
In general features the present species resembles lrα・砂αiαγcα ηαη％odθ8
（MARTIN，1885）from Upper Miocene of Djakarta in Java， Indonesia， but H．
ηαηηodθ8 can be distinguished from the present one by having a little larger and higher shell and less oblique posterior margin．
D伽θη8ioπ8（in mm）：−Height 5．4， length 10．0， depth ca．3．5．
Oc6％γγθ％6θ：−Loc．2（Rare）．
Gθolog乞c砺8￡γ b％励η：−Tokazan Formation， Taiwan；Nakoshi and Shin−
zato Formations， Okinawa Prefecture；Takanabe Member of Koyu Formation，
Miyazaki Prefecture；Ninomiya and Naganuma Formations， Kanagawa Prefec−
ture；Kiwada and Narita Formations， Chiba Prefecture；Hatsuzaki Formation，
Ibaraki Pref㏄ture．
Rθ6θ励碗8扮6b％￡づo％：−Honshu（Boso Peninsula and Noto Peninsula as north limit）， Shikoku and Kyushu．
GθoZo9 ￠γαη9θ：−Pliocene to Recent．
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 11
Genus AηαdαγαGRAY，1847 Subgenus ro8αγ￠αNODA，1965
≠1γzα∂αγα （欠08αγ6α） 8θ∂αηθγz858 （MARTIN，1910）
1910．
1942．
1966．
∠4γCα （S￠αpんαγCα） 8θ｛彦α％θη8 8 MARTIN． Sα1れ7ηZ． Gθol．1e．1ぽμ8．， Lθ掘θγZ，
2V． F．， Bd．1， Heft 1， p．381， pL 54， fig．125−127．
Aπαdα㍗α（8cαpんαγcα）8θ∂αηθη8短． YABE and HATAI，」αp耽． Jo耽． Gθol．
Gθoργ．，voL 18， nos．1−2， P．73， PL 7，69．9．
∠4παdαγα（To8αγoα）8θdαηθη8i8． NoDA， Sci． Rθp．， roみoんμU励 ．，2nd Ser．，
vo1．38， no．1， P．123．
Rθ勿α袖8：−One imperfect but well preserved specimen was examined． The present species is characterized by its large， subtrapezoida1， inHated shel1， numer−
ous， squarish， dichotomous， beaded radial ribs and depressed area along the posterior side．
1）伽θηsZoπ（in mm）：＿Height 48．0．
0￠斑〃グθ？z6θ：−Loc．5 （Rare）．
Z） 8佐茄μ励η：−Middle Miocene Formatiolls， Java；Pliocene Nakoshi For−
mation， Okinawa Prefecture；Byoritsu Formation， Taiwan．
σθoZo9ゼ￠γαη9θ：−Pliocene．
Subgenus 80αPんαγoαGRAY，1847
／1％α∂αγα （ScαPんαγoα）ηo（Zα MAsuDA， SATo and SHuTo， n． sp．
P1．1， Figs．7a−b，8，9a−1），10，11a−b，12
1965．ノ4παdαrα（Soαpんαγ￠α？）sp． NoDA， rγαη8． Pγo￠．
N．S．， no．59， P．101， pl．10，6gs．8，9．
Pα1αθo砿So￠．」αPαη，
1rolo垣pθ：−GI（−1」11825．祈
乃pθZocαZ 句：−Loc．5． Yonahama Flormation．
Diαgπ08奄8：−Shell generally medium in size and oblong． Radial ribs stout，
broader than their interspaces and its total number 20 to 22． Ligamental area rather narrow． Ventral margin broadly rounded．
1）θ86γ鋤Zoη：−Shell medium in size， ovately oblong， rather thick， moderately in且ated， longer than high， inequilatera1；anterior side rounded， posterior side elongated， dorsal margin straight， depressed area along Posterior side of shell，
ventral margin broadly rounded． Surface with 20 to 22， elevated， smooth radiaI ribs which are more or less squarish in prome and broader than their inter−
spaces having lamellated concentric incremental lines． Beak small， pointed・and 8trongly incurved anteriorly；1igamental area rather narrow；teeth small， per−
pendicular to straight hinge line and slightly converge ventra11y． Inner sur，
face smooth except for 6ne longitudinal striations withill pallial line and with distinct crenulations along ventral margin．
Co仇Pαη80π：−The present new species somewhat resembles、4ηα∂αγαα城oτ
（NoMuRA，1933）described from the Byoritsu Formation， Taiwan， but it can be distinguished fromα砿oτby its rather large oblong shell and radial ribs
＊Abbreviation for Department of Geology， Kyushu University．
12 Y．SATo， K． MAsuDA， and T． SHuTo
broader thall their interspaces． Also， A％α伽γα （ScαPんα㌘侃）￡α瓦αoθηsi8 （No−
MuRA，1933）from the Kaizan Formation， Taiwan， can be distinguislled from the present one by having smaller shell with about 25 radial ribs which are much broader than their interspaces and 6nely granulated on anterior part．
The present species also resembles A．肋Z8加∫ε（MARTIN）from the lower Middle Miocene Rewbeng Bed of Java， but the former is distinguished from the latter in having somewhat stouter ribs of less number and more oblique posterior margin than the latter．
1万仇θη8 0η8（in mm）：
Valve Height Length Depth
＊Holotype Left＊
20．8 41．0 14．5
Left
30．0 40．0 14．5
06cμγγθη￠θ：＿Common．
θθolo9 6 d！乞8加訪μ抗oη：−Ananai Gθo〜ogicγα？τgrθ：−Pliocene．
1．eft 26．5 38．0 13．5
Right
27．5 42．5 14．5
Rignt
26．0 37．0 11．0
Formation， Kochi Prefecture．
Right
22．0 33．0 10．0
1926．
1958．
1965．
Aηα∂αγα （S6α助αγ6α）8μzμん商 （YOKOYAMA，1926）
P1．1， Fig．13
Aγcα8μ訊腕るYoKoYAMA． Jo耽． Fαc． S￠《．，1mp． U舵初．欠o〃〃o， Ser．2， vol．1，
pt．9， p．368， p1．42，6gs．6，7．
∠4ηα｛1αγα￡γτcθM￠08τα （NYST）．
Pαpeγ， no．4， pl．54， figs．6，7．
Aれ｛㎡αγα （SCαPんαγα叱） 8μZμん碗．
MA．KIYAMA， Pα1αθo励． So￠．」卯〉αη， S匁θc．
NODA，1▼γα舵8． Pγo￠． Pα1〔泥oγは． So￠．」αP．αin，
1V．8．， no．59， p．100， p1．10， figs．3−7，10−13， pl．11，6gs．9，10．
1966． Aηα己α閲（Scαpんαγcα）8μ2碗砿 NODA， Scτ． Rθρ．， Toんo〃μU痂η．，2舵d Sθγ．，
1981．
vol．38， no．1， p．111， p1．8，6g．2．
Aれαdαγα（ScαPんαγcα）8視2漉砿 M．OMOR∬， pl．2，69．1．
25， granulated， squarish
MAsuDA and OGAsAwARA， Mθ物． VoI． Pγo∫．
Rθ祝α祐8：−The present characterized by its rather small shell having about radial ribs which are narrower than their interspaces lamellated concentric lines．
The present species was丘rst described on the basis of the type specimen
from the Tonohama Formation， Kochi Prefecture by YoKoYAMA（1926）and
then it was regarded as a synonym of Aηαdαwα（S￠αpんαγ￠α）抗6￠πi￠08彦α（NYsT）
by MAKIYAMA（1958）． However， it is evident that the present one can be dis−
tinguished fromか乞￠θ励co8fαby its rather small shell and smaller number of granulated radial ribs．
D 抗e循ioπ8（in mm）：−Height 22．5，1ellgth 33．0， depth 10．5．
066z〃γθη￠θ：−Loc．5（Few）．
Gθolog《￠跳￠γ祐％￠ioη：−Tonohama Formation， Kochi Prefecture；Dainichi Formation， Shizuoka Prefecture．
GθoZogicγαηge：−Pliocene．
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 13
Aηα∂αγα （S￠α坤αγ￠α）励oθ励co8￡α PI．1， Fig．14
（NYST，1848）
1844． Aγcαγαd α￠αREEvE． Coηcλ．1￠oη．， vol．2， Aγ6α， sp．40， P1．6，69．40．
1848．Aγ￠α￠冗6θ痂co8￠αl NYsT．刀ぜθ仇．∠4cα∂． Roy． BθZg．， vo1．22， p．74．
1882． Scαpんαγ6αpん伍p戸αηαDuNKER．1η（1θωMoπ． Mαγ．」αpoη， p．236．
1891． ・4γ￠α（8cαPんαγcα）ρん砺ρ獅α％α． KoBELT in］MARTINI und CHEMNITz， Sμs￠．
Coηcん． Cαb．， vo1．8， P．90， P1．25，6gs．1，2．
1928b．ノ4γoα（SoαPんαγcα）PM励〆αη．α． YoKoYAMA，1傾P． Gθol． Sμγ〃．」αPαη， RθP．，
no．101， P．103， pl．17， figs．4，5．
1960． ノ1鋤αγα （Soαρみαγcα）かτ￠θγ乙τco8τα． ］MAKIYAMA， PαZαθo励． So6．」αpαη，
8pθ6． Pαpθγ， no．6， pl．103， figs．4，5．
1965．．4ηα∂αγα （S￠αp輪アoα）診η￠θM￠08￠．α．NoDA， rγ耽8． Pγoc． Pα1αθo励． Soc．
」α3｝αγτ，N． S．， no．59， p．102， p1．10，6gs．1，2，16，17．
1966．．4鋤αγα（Scαp疏γω）￠γτ6θητloo8￠α． NoDA， S￠i． Rθp．， Toんoん祝σητ勿．，2ηd Sθγ．，vol．38， no．1， P．113， P1．10，69．7．
Rθ祝α祐8：−Several rather unfavorably preserved specimens were exam−
ined． The present species is characterized by its e］ongated shell and about 28，
distinct， squarish， granulated， non−dichotomous radial ribs．
0￠￠2〃γθη6θ：−Loc．3．（Rare）；Loc．4（Few）；Loc 5（Rare）．
Gθologτ6碗8掘bμεZoη：−Byoritsu Formation， Taiwan；Nakoshi Formation，
Okinawa Prefecture；Naganuma Flormation， Kanagawa Prefecture．
Rθ￠θ川砺説勿bμ￠ioη：−Honshu （Boso Peninsula as north Iimit）， Shikoku，
Kyushu，1（orea， China， Philippines and Indonesia．
Gθolo9τ6γαη9θ：−Pliocene to Recent．
Genus SεγZαゲcαCoNRAD，1862 8諺γZαγcα γ7τ勿α〜ヒoグτγηαθη8ゼ8 MAsuDA， SATo and P1．1， Figs．15，16a−b
SHUTO， n． sp．
1roZo句pθ：−GK−1．11826．
τ卯θZocαZ 句：−Loc．2．6ura Formation．
1万αρ％08δ8：−Shell generally small in size， ovate and moderately in且ated．
Ligamental area narrow and oblonged triangular． Internal surface striated but 110marginal SerratiOn．
Dθ8cがp励η：−Shell small， ovate， medium in thickness， moderately innated，
subequilateral；ventral margin nearly parallel with hinge line． Beak small，
pointed and strongly incurved． Surface sculptured with numerous， somewhat granulated， low radial ribs， intercalary threads and concentric incremental Iines；intercalary threads usua11y appear near beak and tend to b㏄ome nearly equal with radial ribs in strength near ventral margin． Ligamental area nar−
row， oblonged triangular．且inge slightly curved， with small， numerous teeth．
Interior surface radially striated but no marginal serration；adductor scars bordered with raised myophoric且ange．
Co仇pαγ 80η：−The present new species is closely related with 8￠がαγ￠α 8ε？zθη8i8（THIELE，1931），aRecent species of the South China Sea， but the latter can be distinguished from the present one by its strongly inflated shell， promi−
nent beak， wide ligamental area and intemal marginal serration．
14 Y．SATo，1（． MAsuDA， and T． SHuTo
The present species is also closely related with 8‡γZαγ侃co仇pゲθ88α（MAR−
TIN，1885）from Sonde Bed， East Java， but it differs therefrom in having larger number of radial ribs， intercalary threads and no internal marginal serration．
D伽θη8ZOπ8（in mm）：一
Valve
且eightLength Depth
＊Holotype
Right＊
10．4 15．4 3．8
Right
14．5 19．0 5．0
Right
10．0 14．2
Left
15．0 21．0 5．0
Left
12．0 17．0 4．0
Intact 18．0 23．0 10．0
06￠μγγθη6θ：−Loc．2（Common）；Loc．3（Rare）；Loc．4（Few）．
1844．
1891．
Genus Aγ⑳p8i8 KoENEN，1885 Aγcop8乞88〃mMetがcα（REEVE，1844）
Aγ￠α8び阻？η￠￠γ匂 cαREEvE． Coγτcん．1￠o舵．， vo1．2，ノ1γ￠α， sp．117， PL 17，69．117・
／1γ￠α（Aゲcα）8〃仇祝召￡冗￠α． KoB肌T in MARTINI ulld CHEMNITz， Sび8ち Cα陀￠ん．Cαb．， vo1．8， p．94， p1．25， figs．7，8．
1853． S￠みαγ6α （GαZα￠￠eZZα）8〃M仇e￡η￠α． HABE in KuRoDA，1ZZμ8ε． Cα￠．」αpαη．
8んθZZ8， no．25， p．209， p1．30，6gs．12，13．
1858． Sぴεαγσα （GαZα￠tθIIα）8〃仇仇θτみ￠α． YAMAMoTO and HABE， BμIZ．114αγ．
BioZ． S勧．≠18αγημ8んτ， Toんo〃μU％初．， vol．9， no．1， p．6， p1．2，6gs．19，20．
1961．S￠γiαアcα（GαZα￠Zθ肱）8〃M彬￡w 6α． HAYAsAKA， Scτ． RθP．， roんoWσ痂〃．，
1966．
1966．
1969．
2γ㎡Sθγ．，vo1．33， no．1， p．27， pL 2， figs．9a−b．
S励αア6αo〃α碗τ．NoDA，1b掘．， vol．38， no．1， p．73， pl．4， figs．8，9．
．S励αγoα8〃仇仇θ坑ω． NoDA，乃ぼ．， vo1．38， no．1， p．73．
S励αアαx8〃働仇θ￠みαz． IwAI and SIOBARA， Bμμ． E吻c． Fα6．， H欣08α腕L7η初．，
no．15， pL 1，6gs．3a−c．
1973．8腕αγ6α8勿η働θ励￠α．IToIGAwA and OGAwA， Sの ． Rθp．，㌘oんoんμUη初．，2η（1 Sθγ．，Sρθ￠．γoZ．， no．6， p．71， pl．5，血g．3．
1977． Aγ從p鮪88y仇仇θ励6α． HABE， Sび8￠．刀ぜoZZ．」αραη， p．41， p1．7， figs．11−14．
Rθ仇α袖8：−One fragmental specimen was examined． HABE（1953）described S掘αγ￠α（Gα1αcτθlkL）oyα？励， n． sp． from Wakayama Prefecture and discrimi nated from 8η飢γ6α8び物批e掘cα． But subsequently he（HABE，1977）regarded oyα仇αZ as a synonym of 8γ仇mθ抗cαto represent a morphological type of inland seas of the latter．
0￠￠πγγθ7a6θ：−Loc．5 （Rare）．
Gθologづ6砺8励b励Zoη：−Sawane and Funabashi Formations， Niigata Pre−
fecture；Dainichi Flormation， Shizuoka Prefecture；Takamatsu and Sakishima
Forlnations， Aichi Prefecture；Naganuma and Shimosueyoshi Formations， Kana−gawa Prefecture；Umegase， Narita Mandano and Numa Formations， Chiba Pref㏄ture；Yoshida Formation， Kagoshima Prefecture；Hiratoko Formation，
Isllikawa Prefecture；Nakoshi Formation， Okinawa Prefecture．
Rece励砺3掘bμ励η：−Honshu （Boso Peninsula as north limit）， Shikoku I（yushu， Korea， China， Taiwan， Philippines and East Indies．
Gθolog ￠γαπgθ：−Pliocene to Recent．
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 15 Family Cucullaeidae
Genus Cμ￠2〃αθαLAMARCK，1801 Cμ6％膓Zαθα9γαημZo8αJoNAs，1846
P1．1， Fig．17
1869．
1891．
1891．
CμのzZZαθα ργαπμlo8αJoNAs． REEvE， Coり2￠ん．1￠oク2．， vo1．17， C2ωμZ膓αeα， sp．
2，pl．1，6gs．2a−b．
Cμcμμαθαcoη￠α祝θγα￠α］MARTINI． KOBELT in MARTINI und CHEMNITz，
8〃8￡．Cαηcん． Cαb．， vol．8， p．5， pl．1， figs．3，4， p1．5， figs．1，2．
C視c祝IZαθα9γαημlo8α． KoBELT in MARTINI und CHEMNITz，乃掘．， P．6， pl．1，
69．5．
1926． C祝￠％ZZαθα￠oη￠αれθγα￡α． YoKoYAMA， Joμγ． Fα￠．86i．，1仇P．σ舵初．7▼o吻o，
Ser．2， vol．1， pt．9， p．360， pl．41，6g．2．
1928． Cμ6μIZαθαP助ηo￠αηθη8i8 MARTIN． YoKoYAMA，1仇P． GθoZ． Sμγ ．」αρ耽，
1929．
1930．
1933．
1960．
1960．
1964．
1971．
1977．
1Zθp．， no．101， p．107， pl．18，6gs．4，5．
cμ62εzみ叱θα ￠07zθα？ηe？rαzα．
C徽↓〃αθα（励鋤αSOLANDER， var．
no．1， append．， p．34，6g．40．
Cμ6μZZαθαργ砲砿08α． NOMURA， S￠ゼ． R杉ρ．， roんo肋1mp．ση初．，2η《Z Sθγ．，
vo1．16， no．1， P．44， pl．4，69．2．
0μoμZ友αyrα？τμZo8α． MAKIYAMA， PαZαθoγ2￠． So6．，」αpαη，8ρθ￠． Pαpθ夕， no．6，
pl．104，6gs．4，4a，5，5a．
Cμ6μπαθαρゲαwμZo8α．］MAKIYAMA，1b掘．， no．6， pL 115， fig．2．
YOKoYAMA，乃滅．， no．104， p．17， p1．8，6g．2．
？） 9γα？微Zo8α． KURODA，ヤPθημ8， vo1．2，
Cμ￠μZZαθα励iαεα9γ耽μZo8α．
p．261，翁gs．1，2．
0μ6城αθα励Zo8ασアαπ祝Zo8α．
HABE， BμII． Nα￠． S￠i． Mμ8．， vo1．7， no．3，
KURODA， HAB冗and OYAMA，8θα8乃θZZ8
SαgαγηづBα〃，p．516， p1．70， figs．1，2．
C拠Llzαθα励io8ασγαημ〜08α．
1，2，
HABE， S〃8ε．刀イolZ．」α卿， p．43， pl．7，6gs．
Rθ仇α袖8：−One imperfect specimen was examined． This sp㏄ies is charac terized by its innated shell with obtuse ridge running from beak七〇po8tero ventral corner， numerous， nat， smooth radial threads which tend to be divided into two parts by a shallow longitudinal furrow towards ventral margin and 6ne concentric lines forming fine reticulation．
06の〃γθη￠θ：−1」oc．2（Rare）．
Gθolog o砺8￠γτb％励η：−Dainichi Formation， Shizuoka Prefecture；Tono−
hama Formation， Kochi Prefecture；Byoritsu Formation， Taiwan．
Rθ￠θ励砺8抗bμ励η：−Honshu （Boso Peninsula as north limit）， Shikoku，
］i（yushu China and Malaysia．
GθoZo9 ￠γα？zgθ：−Pliocene to Recent．
Family Glycymerididae Genusαyc〃彿θγi8 da CosTA，1778 α〃6びMθ冗8γo仇批1α（DUNKER，1882）
PI．1， Figs．18，19，20，21
1882．
1889．
Pθc施ηc祝Zμ8γo加η｛抗8DuNKER．1翻εり6 MoZZ． Mαγ．」αpαη．， P．236， pl．16，
6gs．9，10．
Pθ6抗ηc祝Zzt8γo加城視8． PILsBRY， Cα￠．」αραη． Mαア．ハイoZZ． p．150．
16 Y．SATo， K． MAsuDA， and T． SHuTo
1920．
1922．
Pθc仇π6視伽8MPPo励6μ8 YoKoYAMA． Joμγ． CoZZ． Scτ．，1襯P． Uη初． roんびo，
voL 39， art．6， p．168， pl．18， figs．3−7．
Pθc九η侃ω8〃α批1αんαωα乞YOKOYAMA．
6gs．4，5．
16id．， vol．44， art．1， p．190， p1．16，
1927． α〃￠びmθパ8γo掘閲α．］MAKIYAMA，1∬θ襯． CoZI． S￠ ．， Kμo亡01ηゆ．ひ〃初．， S￠γ．
B，vo1．1， no．1， p．31， pl．1， fig．7．
1954． Gらc鋼θ冗8γo毒μ閲α．TAKI and OYAMA， PαZα￠o撹． So￠．」αPαη， Spθc． PαPθγ，
no．2， p1．36，6gs．4，5．
1962． GZ〃￠〃mθパ8γo施城α． HAYAsAKA，欠γαηs． Pγoc． PαZαθαnt． Soc．」αPαη， N． S．，
1971．
1973．
no．47， pl．45，6gs．8，9．
αy￠びMeη8γo飢閲α．
p．532，p1．71，6g．6．
α〃（羽批θ碗8γo‡徽dα．
KURODA， HABE and OYAMA， SθαSんθIls Sα9α慨i Bα ，
OYAMA， PαZαθoη￠． Soc．」αPαη， Spec． Pαpeγ， no．17，
p．77，p1．22，血gs．5，6．
Rθ輪袖8：−The present specimen is charac七erized by the following fea−
tures：−Shell medium to small in size， thick， inequilateral， moderately innated．
Beak small， pointed． Anterior dorsal margin rounded， shorter than broadly rounded posterior dorsal margin． Surface with rather coarse concentric growth lines and numerous， faint，6ne radial threads． Interior surface smooth， but pallial line and adductor scars distinct；distinct serration at ventral Inargin；
1igamental area triangular in shape， with distinct divaricate sculpture．
The present species shows a great variation in shell form． Usually shells are suborbicular in younger stage， but shells tend to become longer than high with growth．
Co伽ραγ 80η：−This species can be distinguished from G勿c〃仇θγZ8勿θ8協α
（DuNKER），aRecent species of Japan， by its muc｝1 smaller， posteriorly protruded shell and faint， fine radial furrows． Also，α〃￠びγηθγτ8〃θ880θη8 8 （SowERBY），
Recent species of Northern Japan， can be distinguished from tlle present one by its large， less in且ated shell， not prominent beak and ra七her distinct radial furrows．
Explanation of Plate 1
Figs．1，2．
Fig．3．
Fig．4．
Fig．5．
Fig．6．
Figs．7a−b，8，9a−b，10，11a−b，12．
SATo and SHuTo， n． sp．，9a−b， Holotype， Reg． No． GK−1、11825．
Fig．13．
Fig．14．
Fig．15，16a−b．
sp．，15，×2．，16a−b， Holotype， Reg． No． GK−L 11826．
Fig．17．
Figs．18，19，20，21．
Figs．22a−b．
Fig．23．
（All figures in natural size unless otherwise stated）
Page ∠4c江α（∠4c α）｛1初αγi6αεα （］HINDS）．1」oc．2．．．．．．．．．．．．．．．．．．．．．8 Cαγτη仇θ伽￠．αγ飢ザθγα（HABE）．×3．5． Loc．4．．．．．．．．．．．．．．．．．．．．．．．9
∧7μcτ4Zα7τα （Tλθ8eylθd！α） sp． Loc．4．．．．．．．，．．．．．．．．．．．．．．．．．．．．．．．． 9 1了αωαiαγcαμ初αθη8乞8（YoKoYAMA）．×2． Loc．2．．．．．．．．．．．．．．．．．．．．10 Aπα∂αγα（To8αγcα）8θ∂αγ2θη8is（MARTIN）． Loc．5．．．．．．．．．．．．．．．．．．11 Aηα｛1αγα （SCαPみαγ6α）ηodαi MASUDA，
1∠oc．5． ．．．．11
・4唖αγα（8￠αPんαγ￠α）8鵬μM （YoKoYAMA）． Loc．5．．．．．．．．．．．．．．．12
、4ηα∂αγα（S￠αpんαγcα）￠γi6θ醐60s毒α（NYST）． Loc．5．．．．．．．．．．．．．．．13 Sεγ乞αγoα仇らα〃oグτγηαθ？τ8τ8MAsuDA， SATo and SHuTo， n．
×1．5． Loc．2． ．．．．．．．．13 Cz￠6㏄〃αθα9アα？zμlosαJoNAs． Loc．2．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．15 α〃￠〃γηεγisγo仇η∂α（DUNKER）． Loc．5．．．．．．．．．．．．．．15 欠μoθ￠oηαんα鵬αωαi（NoMuRA and ZINBo）．×2． Loc．5．．．．．．．．17 1∬o｛1τol視8 sp． 1」oc．2．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．18
Mem． Fac． Sci．， Kyushu Univ．， Ser． D， Vol． XXVI
4蝿豊
16a
16b
♪ノ﹃
9a
11a
20
↓
賓
9b
5
Plate 1
7b 、
ご▲
12
19、
23
瓶
Y．SAToθ￠α1．：Pelecypod Flauna of the Shimajiri Group in Miyako−jima
Mem． Fac． Sci．， Kyushu Univ．， Ser． D， Vo1． XXVI
3b
Plate 2
Y．SAToθ亡α／．：Pelecypod Fauna of the Shimajiri Group in Miyako−jima
Pelecypod Fauna of the Shimajiri Group in Miyako−jima 17 D伽θπ8ioη8（in mm）：一
Valve Height Length Depth
Right
40．0 41．0 11．0 Oc62zγゲθγzcθ：−Loc．4 σθologi6
Right
37．0 37．8 10．0
Right
35．0 34．5 10．4
Left
44．0 47．0 15．0
Left
39．5 40．0 11．5
（Common）；Loc．5（Abundant）
Left
36．5 38．8 10．0
Intact v．
33．0 32．5 20．0
∂ 8〃 b％￠ oη：−Tenno Prefecture； Koshiba and Yokosuka Formations，1（anagawa Prefecture；Jizodo Formation， Chiba Pre−
fecture．
Rθ￠θ励砺8扮ibμ￡ioη：＿Honshu （Tsugaru Strait as north limit）， Shikoku，
Kyushu and East China Sea．
σθolo9ゼ￠γαη9θ：−Pliocene to Recent．
Genus 7％6θ￠07砲IREDALE，1931
Tμcθ￠oηαんα批αωαづ（NoMuRA and ZINBo，1934）
P1．1， Figs．22a−b 1934．
1961．
1980．
α〃￠yMθ丙8んαηzαωαi NoMuRA and ZINBo． Scτ． RθP．，欠oλoW 1γηP．σ励u．，
2γ㎡8θγ勺vo1．16， no．2， p．152， pl．5，6gs．3a−b．
Tμcθ￠oηα（rμ￠θ加η・IZα）ん仇斑ωατ． HABE， CoZ』Zμ8￠． S九θZI8」αPαη， P．112．
pL 50， fig．4．
α〃o〃？ηθηs（rτωθ￠0γaα）んα批αωαi．NODA，＆兇 ． RθP．1η8 Z． Gθ08cf．，ση初．
1▼8初抗bα，Sθγ． B， vo1．1， p．80， p1．2，6gs．14a−b，15a＿b，16a−b．
Rθ勿α夕〃8：−Three specimens were examined． This species is characterizeα by its small， inHated shell with 20 to 25， smooth， rounded radial ribs which are broader than their interspaces and crenulated illner ventral margin．
1）乞物θ鵬Zoη8（in mm）：−Left valve， height 14．5，1ength 12．5， depth 4．5；left valve height 14．0， Iength 12．0， depth 1．5；right valve， height 11．0，1ength 10．0，
dept｝13．5．
0￠の〃γθη￠θ：−Loc．5 （Few）．
σeoloφ6跳仇6％励η：−Shinzato Formation， Okinawa Prefecture；Ryukyu Limestone， Kagoshima Prefecture．
Rθoθ？z渉〔》isかεbμκoη：−Southern Japan．
σθoZo9ゼ6夕αη9θ：−Pliocene to Recent．
Explanation of Plate 2
（AII figures in natural size unless otherwise stated）
Fig．1． Co㎜μoPαZZW仇sp． cf． C． i拠θηsτs（NoMuRA and NIIo）． Loc．5．
Fig．2a−b． ／1？zηα6んZα批y8 sp．（n． sp．）， Loc．5．．．．．．．．．．．．．．．．．．．．．．．．．．．
Figs．3a−b． ・4働μ88 oPθcZθηPゲαθ8igη臼（YoKoYAMA）． Loc．5．．．．．．．．．．．．
Fig．4． GZor句αZκzεηzραZ万μ物（LINNAEus）． Loc．5．．．．．．．．．．．．．．．．．．．．
Fig．5，6，7，8． Cη餌oPθ￠亡θηημりc 8θη乙α亡θη8i8（OYAMA）．×2．5． Loc．5．
Figs．9，10． C万α蹴y8（M物α￠万α？砲8）8αZo5（YoKoYAMA）． Loc．3．．．．．．
Fig．11． ∠4㌘η視8iμ視μθzげoγ↓θ￠杉θ80〃仇α初αθη8τs MAsuDA， SATo and
SHuTo， n． subsp． Loc．2．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．． ．18
Page
．．．．23
． ．24
．．．．19 ．23 ．24 ．21
