九州大学学術情報リポジトリ
Kyushu University Institutional Repository
Neogene Bivalves from Panay Island, the
Philippines : Contributions to the Geology and Palaeontology of Southeast Asia, CVII
Shuto, Tsugio
Faculty of Science, Kyushu University
https://doi.org/10.5109/1544087
出版情報：九州大學理學部紀要 : Series D, Geology. 21 (1), pp.1-73, 1971-10-25. 九州大学理学部 バージョン：
権利関係：
pp．1−73， figs．1−14， table 1， plates 1−10，0ctober 25，1971
Neogene Bivalves ffom Panay the PhUipPines
Island，
C｛肌tγibμtions to the Geobgyαnd Pα』e㎝ωlogy of So城heαst Asiα， CVII
By Tsugio SHUTO
Abstract
This is the second part of the palaeontological study of the younger Caenozoic molluscs of Pallay Island， the Philippines． The material was ob−
tained at four localities of the eastern section of the IlOilo basin in 1964．
Biological consideration and correlation of the fossil assemblages were given in the first part of the report（SHuTo，1969）and systematic descriptions of fourty−nine species of bivalves are treated in this part． Seven of fourty＿nine are neW tO SCienCe．
Contents
Page
Introduction ．．．．．．．．．．．．．．．．．．．．．．．．．◆．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Acknowledgements＿＿＿．＿＿．．．＿＿＿＿．＿．．．＿．＿＿．＿＿＿
Systematic Descriptions＿．．……．．………・・…＿・＿＿＿＿
Measurement of the bivalve shells．．．．．．．．．．．．．．．．． ．．．．．．．．．．．．．．．．．．
Subclass Palaeotaxodonta．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Order Nuculoida．．．．．．．．．．．，．．．．．．．．．．．．◆．．．．．．．．．．．．．．．．．．．．．◆．．◆．．．．．．．．
Superfamily Nuculoidea＿＿＿＿．＿．．．．．．．．．．＿．．．．．．．．．．．．．．．．．．．
Family Nuculanidae．．．．＿．．．．．＿．＿．＿．＿．．＿＿．．．．．．．．．．◆．．．．
Subclass Pterimorphia．．．．＿＿．．＿＿＿＿．．＿＿＿．＿．．＿．．◆．．．．．
Order Arcoida．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Superfamily Arcoidea．．．．．．．．．．＿．．．．．．．．．＿．．．＿．＿．．＿．．．．
Family Arcidae．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．＿．．．．．．．．．．．．．．．．．．．
Family Noetiidae．．．．．．．．．白．．．．．．．．．．．．．．．．．．．．．＿．．．．．．＿．．．．．．．．．．
Family Glycymerididae．．．．．．．．．．．＿．．．＿＿．．＿＿＿＿．．．．．．．．．．
Order Pterioida．．．．．．．．．．．◆◆．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Suborder Pteriina．．．．．．．．．．．．．．．．．．．．．．．．φ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Superfamily Pectinoidea．．．．．＿．．．．．．．．．．．．．．．．＿．．．．．．．．．．．．．．．．．．．
Family Pectinidae．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．◆．．．．．．．．．．．．．．．
Suborder Ostreina ．．．．．．．．．．．．．．．．．．．．．．．．◆◆．．．．．．．．．．．．．．．．．．．．．，．．．．．．
Superfamily Ostreoidea．．．．．．．．．．．．．．．．．．，．．．．．．．．．．．．．．．．．・．．・．． ． Family Ostreidae．，．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Subclass Heterodonta．．．．．．．．．．．．．．．．◆．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Order Veneroida．．．．．．．．．．．，．．．．．．，．．．．．．．． ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
Superfamily Lucinoidea．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．
225566669999222527272727282828292929
Manuscript received May 31，1971．
T．SHUTO
Family Lucinidae．．，．．．．．．．
Superfamily Leptonoidea．．．．
Family Kelliidae．．．．．．．．．．．
Superfamily Carditoidea．．．．．
Family Carditidae．．．．．．．．．
Superfamily Cardioidea．
Family Cardiidae．．．．．．．．．，
Superfamily Tellinoidea．．．．．
Family Tellinidae．．．．．．．．．．
Family Psammobiidae．．．．．
Family Solecurtidae．．
Superfamily Veneroidea Family Veneridae．．．．．
Order Myoida．．．．．．．．．．．．．．．．．．
Suborder Myina ．．．．．．．．
Superfamily Myoidea．．．．
Family Corbulidae．．
References Cited．．．．．．．．．．．．．．．．．
・ ● ●
・ ・ ． ● ● ． ● ● ● ■ ■ ● ● ● ● ■
・ ． … ． ・ ・ ・ ・ … ■ ・ ・
●
… ． ● ． ● ． ・ ． ・ … ● ■
■
●
● ・ ．
・ ． ． ・ ． ● ● ． ● ． ． ● ● ● ・ ◆
・ ． ・ ・ … ● ● ● ● ■ ■ ● ● ● ● ● ■ ◆ ● ● ● ● ■ ● ■
・ ・ ・ ・ … ． ● ・ ● ■ ■ ． ● ・ ● ● ■ ● ● ● ● ■ ● ■ ●
・ … ． ● ■ ● ● ■ ・ ● ● ● ● ● ■ ● ◆ ■ ● ■ ● ■ ● ● ■
． ● ● ● ● ● ● ● ● ■ ● ● ● ● ■ ● ■ ● ● ● ● ● ■ ● ● ●
・ ・ ． ． ● ・ ・ ● ● ● ● ● ■ ■ ■ ■ ● ■ ● ● ■ ● ● ● ■ ● ●
・ ・ ・ … ． … ． ． ． ・ ． ・ ・ ． ● ・ ． ■ ・ ・ ● ● ふ
・ ● ■ ● ■ ● ● ● ● ● ● ● ■ ● ■ ● ● ◆ ● ● ● ● ■ ■ ■ ●
・ ・ … ． … ● ・ ・ ◆ ・ ■ ■ ■ ● ◆ ■ ■ ■ ● ● ● ●
． ● ● ■ ・ ・ ● ● ● ● ■ ■ ■ ● ■ ■ ■ ● ■ ■ ● ● ●
◆
■
． ■ ● ■ ● ● ■ ● ■ ● ● ● ● ● ■ ● ■ ■ ● ● ● ● ● ■ ． ■
911223377912255558233333333455566666
Introduction
The geologic sequence of the Iloilo basin in Panay Island， Central PhilipPines，
have been regarded as a type section for the Neogene biostratigraphy in that
country． Reexamination of the type sections of that basin was undertaken as a part of the project， the palaeontological reconnaissance of the Southeast Asia supervised by Professor R． ToRIYAMA of Kyushu University and Professor Emeri−tus T． KoBAYAsHI of the University of Tokyo． The field work was carried ouhn
November of 1964 by Drs． T． KANAYA of Tohoku University and T． SHuTo of
Kyushu University with the colaboration of Messrs． S． A． GoNz飢Es and P． J．SANTos of the Pe七roleum Division of the Bureau of］Mines， Republic of the
PhilipPines under七he conduct of Professor I（． AsANo of Tohoku University． Themolluscan material obtained on that occasion was s七udied by SHuTo and the
general consideration on the fossil assemblages and the sys七ematic descriptions of the gastropods were given in the preceding report， Neogene gastropods from Pallay Island， the Philippines，，， as the contributions to the Geology alld Palae−ontology of Southeast Asia，， No．68（SHuTo，1969）． The present repor七is the
second part of the s七udy and contains the systematic descriptions of 49 species of bivalves， of which seven are llew to sciellce．Acknowledgements
On printing the present work tlle writer wishes to express his sincere thanks to several persons， who gave valuable assistance， advice and co−operation in the course of the study．
Professor Ryuzo ToRIYAMA of I（yushu University and Professor Emeritus
Teiichi KoBAYAsHI of the University of Tokyo promoted the project． The Bureau of Mines of the Republic of the Phillippines directed by］M［r． Fernando S． BusuEGo gave the effective support to the Japanese party． The Petroleum Division col1一ducted by Mr． Felipe U． FRANclscO enabled the field work of七he Japanese party with their full co−operation． Particularly the writer is indebted to Messrs．
8enjamin A． GozAEs and Perfecto J． SANTos．
The great number of books and molluscan specimens were needed for the
taxonomic work． The writer is indebted in access to the llecessary material and literature to Dr． Tadashige HABE of the National Science Museum of Tokyo， Dr．Ka七ura OYAMA of the Geological Survey of Japan， Dr． Masuoki HoRIKosHI of the University of Tokyo， Professor H． J．］MAcGILLAvRY of the University of Amster一
Table 1．
specles fossil locality in
Panay SKGS一
known geologic and geographic range 1乙O
QU
4 5
6 7 8
γo硫α（0γ鋤〃o硫α）∫γαη一
ロ コ
仇8coτsp・nov・
SαocθIZαραηαびθηsi8 sp． nov．
欠ゲゼsε（lo8 sp． cfr． 欠． 8θ？ητ一
￠0γ￠α（1」AMARCK）
Aηαdα夕α（s6αPみαγcα）が1祝1α
（REEVE）
〆1．（s．）σθ掘仇9αηθη8i8
（MARTIN）
A．（∠4ηαdαγα）￠α励α6αηα
（MARTIN）
A．（・4．）輪んoZo仇α
（DESHAYES）
A．（∠4．）グθγw9屹α（REEVE）
9 A． （A．） Zμ20？包τCα 1）毒θγτγη0γ一 Pんαsubsp． nOV．
10
1←噌⊥1⊥呼⊥噌
⊥2 34
15
16 17 18 19 20 21
ZL（∠4．）bμMθ8Z（D，ARCHIAC et HAIME）
A．sp．
AγcOP8《s bα毒αぬ舵α
（MARTIN）
S彦ゲ伽6αZα仇紗（KOPERBERG）
ルfθzαo 拠θαPθ6励i∫oγγ嬬
（LAMARCK）
Cん鋤れびs（M伽Lαcん1α1町ノ8）sp．
cfr． C． （11Z．） sカτ9αpoγτη祝8
（SOWERBY）
08紗eα（08舵α）gl醐θγα￠α
GOULD
L仇ρα（BθII視￠仇α）go酩αle8 sp・nov．
ハイαパ〃θ」屍α Pα？ταμθγL8i8 sp．
nOV．
Cα働ocαγd伽グαuαηα
（MARTIN）
悟α9μ祝（L協硫cαγ∂鋤8祝b一 γθ枷sα（SOWERBY）
Lαθ屹αγ∂㌦仇（F祝励α）sp．
71
14
ワ．ワ・71and 73
7371and 72
74 71，72，and 73
74
71
42
7・7・44
7ワ●71
72 71 71 74 73 71
Plio．（Timor）， Low． Pleist．（Taiwan），
Rec．（Southeast Asian waters）
Plio．−Pleist．（Indonesia and Taiwan），
Rec．（Philippines）
Plio．（Java）
Up． Mio．−Plio．（Java）， Plio．（South India）
Plio．（Timor and Seram）， Rec．
（Southeast Asia to North Australia）
Plio．（Java and Timor）， Rec．（South−
east Asian waters）
another subspecies， 1）αη9んαθγλ8Z8
（MARTIN）and診θγんααγi（OosTINGH）
from Plio．（Java）．
Up． Mio．−Plio． （Indonesia and
Burma）
Up． Mio．−Plio．（Java and Timor）
Up． Plio．（Timor）
Plio．（Java）， Rec．（Southeast Asian waters）
Rec． （South China Sea， Indian Ocean， Red Sea）
Up． Mio．−Pleist．（lndonesia）， Rec．
（Southeast Asia to New Zealand）
Up． Mio．（Java）
Low． Pleist．（Taiwan）， Rec．（South−
east Asian waters）
T．SHUTO
Table 1．（Continued）
specles fossil locality in
Panay SKGS一
known geologic andgeographic range
9●nδ49一9一〇乙
25 6ワ・9一9臼
80VO
9一9一〇〇噌⊥9一
〇δ
00 33 34 35 36
γθPγτ6α7て況2〃η？sp．
Pγo￠ooαπ況αsp．
Tθz励α（Lαcτol仇α）仇oαγ一 れα￠αb視8％θgoZ subsp． nov．
r．（P耽iρα9乞α）ゲo￠耽dα
MARTIN
T．（P．）pμ〔IZcαHANLEY 欠．（Aγ60Pα9拠zα）仇βαzα
GMELIN
77．（、4．）sp．
欠．（SeγηθZαγτ9μZZL8）sp．
τ．（1↓foθγθZZα）拠耽odθ8
MARTIN
欠．（疏o比α）sp．
欠．（1匪θ万80α）硫Pんαηα
（DESHAYES）
λfα6鋤α （A％8か0仇α60㎜α）
￠θ励αbθ旭8（］MARTIN）
Gαγゼ（Gα碗）ρμ励θzzα
（1」AMARCK）
G．（GobγαθZLS）sp． cfr． G．（G．）
cγα88μZα（DESHAYES）
Azo痂祝8（加oγ仇μ8）αbbγθ一 励α毒2偲（GOULD）
37 C汐cθγ初μZαγi8（BORN）
38 Mθ㌍θ紗㌘伽θγθぴ伽（LINN1き）
39 LZo60？τ6んα（SμZ￠ZZio607乙cんα）
ρんZ励p仇α仇（HANLEY）
40 ．Do8iγzτα （Pんα￠080γηα） θ06一 α8ρθγα￠α（PHILIPPI）
41 CZθ？ηθ7Lだα （CZθ？ηθγτ］％α） 匁α一 ρyγα6θα（GRAY）
42Pαρんiα（Pαゲα￠αPθ8）μηdμ一 ZαZαηθgZθ￠亡α（MARTIN）
43 P．（五7μγηαγciα）6九θγτboηeη8τs
OOSTINGH
44 」PZα6α？ηθη 6αloρん〃ZZα （PHILIPPI）
45 46
47 狙vθγθ㈱ゆbα￡α悦αηα
（MA．RTIN）
γ．￡吻0ηαZi8（MARTIN）
γ．σo㍑αZθ8Z sp． nov．
CoゲbμZα（Coγbμ α）80αPんoi−
dθsHINDS
49 C． （∠4η《80COγbμ α）
MARTIN
806iαli8
−占901占
777
72
71
71and 73
9●3噸⊥ワ・ワ・ワ・−凸3ワ・ワ・
71
71and 73
73 71
δ0 3
ワ・ワ●
73 71 73
71and 73
71and 73 71and 73
71
449一47・7ワ・
74
Mio．（Java）
Rec．（Southeast Asia to Japan）
Up． Mio．−Plio．（Indonesia）， Rec．
（Southeast Asian waters）
Plio．（Java），1・ow． Pleist．（Taiwan）
Rec．（Southeast Asia
Japan）Low． Mio．（Java）
Rec．（PhilipPine waters）
Rec．（Phllippine waters）
to Sout11
Low． Pleist．（Taiwan）， UpP． Pleist．
（South Japan）， Rec．（Southeast Asia to Japan）
Rec．（Southeast Asian waters）
Low． Pleist．（Taiwan）， Rec．（South−
east Asian waters）
Plio．（Timor）， Rec．（Southeast Asian waters）
Rec．（Southeast Asian waters）
Low． Mio．−Pleist．（South and South−
east Asia）， Rec．（Indo−Southwest Paci6c region）
Mio．−Plio．（Java and Borneo）
Plio．（Java）
Mio．−Plio．（Philippines， Indonesia，
North Borneo），1、ow． Pleist．（Tai−
wan）， Rec．（Southeast Asian waters）
Up． Mio．・・Plio．（Java）
Up． Mio．−Plio．（Indonesia）
Plio．（Timor）
Up． Mio．−Pleist．（South and South−
east Asia）， Rec．（Southeast Asian waters）
Low． Mio．−Plio． （Indo−Southwest Pacific region）
dam， Dr． C．0． van Regteren ALTENA of the National Museum of Na七ural History in Leiden， Dr． C． BEETs of the National Museum of Geology and Mineralogy in L，eiden and Dr． Henny E． CooMANs of the Zoological Museum of the University
of Amsterdam．
Sincere gratitude is also due to the Ministry of Education of the Japanese Government for his 6nancial aid both to the field and the laboratory work．
Systematic Descriptions
Measurement of the bivalve shells
The bivalve shells are measured at several dimensions such as length（L），
height（H），depth（D），length of the anterior part before七he umbo（La），length
of the lunule（U），umbonal angle（∠U）， and number of the radial and concentric sculpture． Taxodont bivalves are also measured at the length of the hinge line（Lh）and the numl）er of the hinge teeth on the an七erior and posterior rows， if the hinge is differentiated in七〇two rows． Some of the quadrate shells such as TθZZ仇αare measured at the height between the subparallel ven七ral and postero−
dorsal margins（Hd）．
Lis de6ned here as the maximum length between the anterior and posterior margins（1 and 6 in text−ng．1）． H is the measure of the distance between the umbo and the tangent of the ventral margin parallel to the measured line L（1 and 6）． 1λa is represented by the length of the anterior part on the line 14 before
the crossing of the measured lines L and H（1 and 6）． Definition of∠U is somewhat complicated． It is represented by the angle formed by七wo tangential
lines of the postero−and antero−dorsal margins． If either of the dorsal margins is convexedly arcuate，七he tangent at the mid−point of the arc is chosen（left hand part＝posterior part of l and right hand part＝anterior part of 4）． While it is1
∠u
L
3
2
L
Lh
7
8
Fig．1． Measurements of the bivalve shells．
T．SHUTO
concave， the line should be tangent both to the umbonal area and the convex remote part of七he dorsal margin（right hand part＝anterior part of l and left hand part＝posterior part of 4）． The radial sculpture may be counted separately on the anterior， main and posterior surface， if the surface is divided in七〇 the parts． The concentrics are counted at an unit distance on the line connecting the umbo to the middle part of the ventral margin and expressed in the formula of， for example，10／3（1−4），which means that the concentrics are 10 per 3 mm be七ween l and 4mm from the ventral margin on the measured line（8 in text一
負9．1）．
Class Bivalvia Subclass Palaeotaxodonta Order Nuculoida Superfamily Nuculoidea Family Nuculidae Genus yoZ（況α］M6LL，ER，1842
（type−sPecies：yoZd αん〃2）θγ〜）oグθαToRELL ［pro I701〔liααγ℃甜cαM61」LER，
non IVz￠c％1ααγc翻cαGRAY］by subsequent designation，
GARDNER，1916， ICZN 19660pinion 769）
synonym：1腕6γoyo磁αVERRILL et BusH，1897（type−species：
y．ゲθ9％1αγ 8VERRI肌， by O． D．）
欠θ忽Z（lolθ（1αIREDAL、E，1939 （type＿species：T．1α彦αoγioη IREDALE by O． D．）
Subgenus Oπ1乞oyol碗αVERRI口et BusH，1897 （type−species：Yol（Ziα86αPα？ziαDALL・by original designation）
yo磁α（0γ仇o〃o協α）アグα煽860 sp． nov．
PL 1， Figs．1，2and 3 and Text−fig．2
Mα￠θ冗αZ．−Holotype：GK−L 7057 （left valve） and paratypes：GK−L 7058
（righ七valve），7059 （right valve），7060 （right valve） and 6575 （right valve）
from one and the same locali七y． Preservation is excellent．
1』fθα8Z〃θ？ηθγzτ8．一
speclmen GK−L
7057 7058 7060
speclmen GK−L
7057 7058 7060
L
（mm）9．5 8．1 8．7
且
（mm）
5．9 5．15 5．4 teeth ant． post．
19 21 18 19 10 20
D
（mm）
2．25 2．0 2．05
valve
left right right
H／L
（％）
62．0 63．5 62．0
D／L
（％）
23．7 24．7 23．6
1、u
（mm）
3．8 3．3 3．5
Lu／L
（％）
40．0 40．7 40．2
∠u
（degrees）
137．9 140．9 140．3
D αgη08 8．−The shell is moderately small， moderately thin， subelliptical and polished． The umbo is hardly elevated above七he dorsal margin and situated at the anterior two−fifths of the shell−length． The anterodorsal margin is almost straight， converges with七he longer posterodorsal margin at the angle of about
140degrees and continues to the anterior margin with narrow curvature． While
the posterodorsal margin forms a blunt angle with the posterior㎜rgin， which
is not rostrate at al1． The ventral margin is broadly arcuate． A very ol）soletefold running from the umbo to the postero−ventral corner separates the com−
pressed posterior part from the main surface． The surface is provided with fine and close concentric striations． In addition a few coarser and sliglltly oblique striations are discernible at the anterior and middle part of七he ven七ral border on the adult specimens． The lunule is weakly de6ned by a ridge， while the concave escutcheon is bordered by a sharp ridge．
The hinge line is divided into two series， which are slepara七ed from each other by the distinct and triangular resilium pit． The anterior series has a slightly small number of the teeth than the posterior one． The tee七h are thin，
erected and tall． The anterior adductor scar is rhomboidal and larger than七he elongate posterior one． The pallial sinus is moderately wide and no七very deep
⊃
3
Fig．2． 1and 2 Sα66θIIαpαηα〃θη8i8 sp． nov．， GK−L 6636， right valve．
1：interior view showing adductor muscle scars and pallial line．
2：umbonal view．
3and 4 γol碗α（0γτんoびo硫α）∫γαη6i8￠o乞sp． novっGK−1」7058， right valve．
3：prodissoconch．4：umbonal view．
Broken Iines indicate outline of the hinge teeth． Unit bar a repre−
sents 3mm for 1，2and 4 and bar b does lmm for 3．
T．SHUTO
on the juvenile specimen but somewhat narrow and remarkably deep with the
bluntly round apex Ilear the beak on the adult specimen． The pedal s℃ar ismoderately large and deeply impressed immediately below the beak． Another
linear scar is visible belo．w the umbo toward the antero−ventral part．The prodissoconch is distinct． It is ovoid， almost equilateral but wi七h the slightly Ionger anterior side than the posterior one．
Oo働Pαγゼ80η．−The present specimens are superficially slimilar toγo協θIZα VERRILL and BusH，1897， bu七the former is readily distinguished from七he latter being provided with the deep pallial sinus． The specimens are better included
in O夕抗o〃o磁αVERRI肌and BusH，1897，0n the basis of the important character−
istics of七he hinge teeth， pallial sinus and adductor muscle scars， although the former is de6nitely less elliptical with smaller umbonal angle than the latter．
The species of O夕仇oγol∂ αhas not been known from the Indo−west Paci6c region．
The present specimens are characterized by their compressed glossy shell with rather small umbonal angle and faint oblique ventral sculpture besides the
important interior features mentioned al）ove． They resemble Lθ肋α1∫％W6α
FIscHER（1927， p．116， pl．216， fs．104a， b and c）from the Pliocene of Timor，bu七are easily distinguished from the latter in having a more compressed and
wider posterior area and weaker sculpture． yoZ（Zτα（0γ仇o〃o硫α）o〃α1τ8 GABB（1873，p．255；PILsBRY，1922， p．402， text一丘g．34；WooDRING，1928， p．22， pl．1，
fs．20 and 21）is a laterally elongate species， from whicll the present specimens differ in having higher shell with smaller umbonal angle． The present specimens should represent a distinct species．
yol砺αZepτ吻1αA． ADAMs（1856， p．50；REEvE，1871， pl．2， f．7）， an ally to the present SPecies， also shows larger umbonal angle and less arcuate ventral margin with straig批part at the middle than the latter．
Lo6α蹴び．−SKGS−71．
∬oグ伽η．−Cabatuan Formation．
Genus Sα￠cθIIαWooDRING，1925
（type−species：イ4γcαかαg砺8 CHEMNITz＝Lθ∂α60ητ仇％τα6αPHILIPPI by original designation）
8α￠cθIZαP砺α〃θ％8i8 sp． nov．
P1．1， Figs．4−7 and Text−fig．2
2胚αZθがαL＿Holotype：GK−L 6635 （1eft valve） and paratype：GK−L 6636
（right valve）from one and the same locality。 Preservation is excellent．
Mθαs微θ抗θ励8．一
m ㎝
↓
35 36隈㏄防
S
m ㎝
壬
35 36K d
66 66
㏄ G
S
L
（mm）
13．65 9．05 teeth
numb．
22 16
H
（mm）
7．25 4．7
D （mm）
2．9 1．8 1irae
numb．／mm
10／3（1−4）
10／2（0．2−3．2）
1、a H／L
（mm） （％）
6．5 53．2 4．5 51．9 valve
LR
D／L
（％）
21．3 19．9
1・a／L ∠U
（％） （degrees）
47．6 143．7 49．7 155．2
DZαgη08Z8．−The shelI is small， pear−shaped and glossy． The umbo is situated almost at the middle． The antero−dorsal margin is slightly convex， while七he postero−dorsal one is slightly concave just behind the umbo． The ventral margin is broadly arcuate continuing to the narrowly rounded anterior end． The pos−
terior part is tapered to the weak rostra七ion． The surface is regularly curved except for a slight depression along the postero−dorsal margin． The lunule and and escutcheon are very clearly defined by the sharp ridges． The sculpture con−
sists of regular concentric lirae， which are much wider than the interstices．
They are finer and more raised with a round top at the early s七age and become flat separated only by striae at the Iater stage． Number of the lirae is about 3．5per l mm and abou七5per l mm respectively at the ventromedian part of the adult and juvenile specimens． The hinge teeth is divided by the resilium pit into
the anterior and posterior rows， of which the former has somewhat more
numerous teeth than the latter． The adductor muscle scars are indistinct． The pallial sinus is moderately shallow．Co伽pαγ乞80％．−The present specimens resemble 8碗6θIZα8θ物ατθπsぜ8（SuzuKI et IslzuKA）（1943， p．48， pl．1， f．3）from the lower Pleistocene of central Japan，
but the former is Iaterally longer with a more pointed rostrum． Fur七hermore
the sculpture of S．8θγηα￡θ％8is is coarser．
Comparing with Nμ￠μ1αηαbα励α働θη8i800sTINGH（1933， p．196， f．10）， the
present specimens have coarser sculp七ure and a more broadly arcuate ventral
margln．
The present specimens are similar to Lθ肋％o砂αθ9励ηθθηsi8 SMITH（1885，
p．237，pl．19， f．10），which is included in Sα66θIIαwith typical features， but the latter has a higher shell with a small umbo leaning anteriorly．
Lo￠αZZ勿．−SKGS−71．
Ho惚oη．−Cabatuan Formation．
Subclass Pterimorphia Order Arcoida
Superfamily Arcoidea
Family ArcidaeSubfamily Arcinae
Genus T冗8τ（los R6DING，1798（type−species：Aγ￠α￠oγ￠τzo8αLINN重， by original designa七ion）
synonym：TγZ8i80KEN，1815（obj．）
PαゲαIIθlopη）θ∂iμ？γτ M6Rc］［1，1850 （obj．）
1恥）πγZ3τ81REDALE，1939 （type＿sp．：Aγoα8θγη祝oγ￠α LAMARCK， by O． D．）
丁灼8元db8 sp． cfr． T．8θM撹oγ亡α（LAMARCK）
P1．4， Fig．17
1835． ／1γ6α 8θγη社oγ￠α p．460．
LAMARcK， Anim． sans vert．（DEsHAYEs， edit．）Vol．6，
T．SHUTO
1844．
1891．
1928．
∠4㌍￠α8θ物従oγ毒α，REEvE， Conch． Icon． Vol．2， Aゲoα， pl．13， f．89．
∠4γ6α（PαγαIIθ10P 匁θδiZ〃η）8θ仇党oけα， MARTINI et CHEMNITz， Conc11． Cal）．
Bd．8， Abth．2， p．134， Taf．35， fs．1−2．
∠4γ6α （PαγαZZθZoμρθ（1飢仇）加γ施osα， YoKoYAMA， Imp． Geol． Surv． Japan Rep． No．101， p．105， pL 16， f．2．
ハ4α￠θがαZ．−GK−L 6675 and 6676． Both the specimens are fragmentaL 丑fθα8％γθ働θ励8．−Llength of the preserved part：43．1 mm；height of the pre−
8erved part：222mm on GK−L 6675．
刀θ8励p励θγθ糀α袖8．−The shell is moderately large and elongato−quadrate．
It is distorted around the hinge axis， judging from the curvature of the ventraI
margin and the posterior shell surface． The decussa七e sculpture consists of alternating radial threads and regularly spaced concentric lines． The cardinaI
area is broken o仕．Co仇pα夕680η．−The specimens should be included in Tγゼ8砿08 R6DING，1798，
on the basis of the distorted， la七erally elongate shell with irregular sculpture，
although the hinge can not be examined． Moderate distortion of the shell and
Fig．3 Umbonal view of Aηα∂αγα（ScαPみαγ￠α）μZ耽α（REEvE）showing the ontogenetic change of the ligamental area and relative depth of the valve（D／L）by the growth series．
1：GK−L 6622，2：GK−L 6621，3：GK−1、7480−7481，4：GK−L 6633，
5： GK−L 6632，6： GK−L 6630，7： GK−L 7479． All the figured specimens came from Ioc． SKGS−71．
Unit bar represents 10 mm for all the specimens．
rather strong sculpture suggest that the specimens may belong to T．8θ励Zoγ渉α 1」AMARCK．
LocαZZ句．−SKGS−74．
丑o冗zo％8．−Pliocene of Timor and part of the Dingle Formation．
Lower Pleistocene of Taiwan． UpPer
Subfamily Anadarinae Genus Aηα∂αγαGRAY，1847
（type−species：Aγ6αα励 σμα￠αLINN亘by original designation）
Subgenus S6αPんαγcαGRAY，1847
（type−species：Aγcα仇αθσ励rりαZ励8 BRuGuI嵩RE by original designation）
Aηα∂αγα（SoαPんαγ￠α）pZIμ1α（REEVE）
P1．2， Figs．1−6 and Text−fig．3
1844．
1844．
1891．
1910．
1933．
1966．
〆1γcαpτZ刎αREEvE， Proc． Zool． Soc． London， p．39．
ノ1γoα傾膓刎αREEvE， Conch． Icon．， Vol．2，∠4γcα， p1．2， f．8．
A㌍￠α（∠4ηoγηαlocαγ∂τα・）餌Z視Zα， KoBELT in MARTINI and CHEMNITz， Conch．
Cab． Bd．8， Abt．2， p．108， Taf．28， fs．7−8．
∠4γoα（∠4ηα吻ゲα）γんo推bθα，MARTIN（partim）， Samm1． Geo1． Reichs−Mus．
N．S． Bd．3， Abt．2， p．368， Taf．52， fs．89−92．
∠4γ6αも4γoα）祐α励θα，NoMuRA， Sci． Rep． Tohoku Imp． Univ．2nd Ser．，
Vol．16， p．37， pl．4， f．13．
Po励γcαp伽1α， HABE and KosuGE， Shells of the World in colour， Vol．2，
p．125，pl．46， f．5．
．Mατθγ鋤．−GK−L 6285，6286 （conjoined），6287−6313 from loc． SI（GS−73，
GK−L 6621，6622（conjoined），6623−6633 and 7479−7482 from SKGS−71．
1∬θα8似膓ゲθ抗θγ↓￠8．一
speclmen GK−L
6285 6287 6288 6289 6292 6306 6307 6308 6309 6310 6621 6621 6622 6623 6624 6626 6627（mm）
18．0 19．4 19．2 18．8 16．75 29．8 28．65 26．4 25．8 23．7 15．4 15．2 11．6 18．45 19．4 16．7 15．45
H
（mm）18．2 19．6 20．45 18．55 16．45 29．35 27．95 26．5 25．35 23．9 16．05 15．25 11．45 19．50 19．6 16．1 15．6
D
（mm）15．45 9．45 9．6 8．35 7．5 12．9 13．2 12．5 11．2 10．9 7．6 7．3 9．5 10．0 9．1 7．75 7．15
am3ほAユ旧品96品JOβ一〇JJ＆ほ L伽687861010101195 36766 Lh
（mm）
10．55 11．8 12．1 11．15
9．8 17．5 17．15 14．8 13．7 14．7 8．4
7．25 10．85 11．5
9．4 9．5
H／L
（％）
101．1 101．1 104．4 98．6 98．2 98．4 97．3 100．4 97．9 100．8 100．3 100．3 98．6 105．5 101．0 96．3 100．9
L︶37948303393082843
レ 協 肌 姐 侃 牲 仏 砥 砥 胞 錨 砥 胞 姐 旺 昆 砥 姐 砥
La／L
（％）
35．0 43．8 40．6 43．1 39．4 35．6 37．0 40．2 45．3 41．8 37．7
33．7 36．3 39．7 38．3 40．8
T．SHUTO speclmen
GK−L
6285 6287 6288 6289 6292 6306 6307 6308 6309 6310 6621 6621 6622 6623 6624 66266627
Lh／L
（％）
56．6 60．8 63．0 59．3 58．5 58．7 59．9 56．1 53．1 62．0 54．6
62．4 58．8 59．3 56．3 61．5
teeth
ant．
13 12 13 12
1←i←司⊥噌⊥略
⊥439一
06ワ．3司⊥
呼⊥司⊥−ふ︷⊥
post．
18 17 16 14
〃リワ・8ワ・
噌⊥哨⊥−⊥−占 90り︵り︵b
i⊥司⊥4⊥司⊥
ribs numb．
26
25 24 25 27 27 27 26 27 24 26 25 24 26 25 26 26
Valve
L（conj．）
R R R R
R R
I4（conj．）
R（conj。）
L（conj．）
L
R
Dθ86γ⑳物θ㌘ε仇α袖8．−The shell is medium in size， rather solid， inequivalve with larger left valve than the right one and slightly inequila七eral． It is rhom−
boid orbicular and extremely inHated so as to illustrate almost equal height，
length and depth of the conjoined valves． The umbo is almost central， large and
remarkably elevated above the dorsal margin． The antero−and postero−dorsal
margins・are together short and form the blunt shoulder angle respectively with the anterior and the posterior margins． The posterior Hexure is distinct nearthe umbo and obscure near the distal margin． The sculpture consists of the
regular radial ribs and raised concentric lines． The ribs， ranging 24−27， are squarish with an almost flat top and vertical sides and crossed by the growth lines forming crenulation． On the left valve七he ribs are wider， while they are sligh七ly narrower七han the interspaces and only weakly crenulated on the right valve except for the anterior part． The left valve holds the right one at theventral margin． The inner margin is heavily crenulated． The hinge七eeth are
not colltinuous， bu七separated a七the middle into two series， shorter anterior series and longer posterior one． The cardinal area is sligh七ly inequilateral with shorter and wider anterior part， which has the ligament−free area at the anterior extremity． This part， bordered posteriorly by a sharp oblique groove， is wider at the early stage and becomes narrow later． The posterior aductor scar is close to the posterior end of the hinge teeth， while the anterior one is apart from the anterior end of the hinge teeth．Co物Pαが80η．−The present specimens are quite identical to・4γ￠αpil％1α REEvE（1843， pl．2， f．8）from the Philippines and also closely resemble some of the Indonesian Neogene alld Quaternary specimens of ・4ゲ6αグんo批bθαBoRN of MARTIN． Aroα〆1μZαis inequivalve with the larger left valve than the righ七〇ne and whole ribs on the left valve are crenulate while only the anterior ones are so
on the right valve according to the original author． He also mentioned that
A．rんo推b￠αBoRN（1778， p．90；KoBELT，1891， p．57， Taf．16， fs．5−6）is equivalvewith the extremely high and Iarge umbo and the prominent posterior丑exure and
its right valve is provided with the distinct crenulation as on the left one． This indicates that A． pZI秘1αand A．㌍んoγηbθαbelong respectively to the di」ぽerent sub−
genera and some of the Indonesian fossil specimens of A．励o勿bθα ， may really belong七〇A． P祝秘1α．
The present material consists of a fairly good皿mber of the specimens from two localities， illustrating a growth series． The s・ample from loc． SKGS−71 does not show any basic difference from the sample from loc． SKGS−73． The growth series exhibits clear allometric development about some characters． The relative dep七h of the valve to the length becomes larger in the course of the growth． The cardinal area also shows allometry concerning the relative length of the anterior and posterior halves and the relative width of the ligament−free area to the whole area． At the early stage the anterior part is extremely short occupying only one fourth of the whole Iength and increased its relative length gradually to attain two一血fths of the whole length． The cardinal area is smooth and not quite on one plane but curved up Posteriorly to the rim at 6rst． At七he jllvenile stage a distinct oblique groove below the beak appears to separate the ligamental area from the ligamen七一free area of the anterior part． The ligament−free area is relatively wide at first and then gradually becomes narrows as mentioned before．
．Aγcα（A？zα肋ゲα）8αb励αθMo肌ET（1889， p．189， pl．8， f．6）from Indo−China shows so closely resembling features wi七h the presen七species that the speci6c distinc七ion seems to be baseless．
Lo￠αliκθ8．−SKGS−71 and 73．
Hoγ花oηs．−Pliocene to Recent in Southeast Asian waters． The Cabatuan and the Ulian Formation in Panay．
A？τα〔1αγα （S6αP〃αγ6α） 9￠？τ（況γzgαηθη8i8 （MARTIN）
P1．3， Figs．5，12 and 13 and Text−fig．4
1910．∠4γ￠α （S6αψαγoα）9θ励i砲耽θπ8ぜs MARTIN， Samml． Geo1．
Leiden N． F． Bd．1， Abt．2， p．381， Taf．54， fs．121−124．
Reichs−Mus．
Mα￠θWα1．−GI（−L 6363． A single left valve．
1レfθα8％γθ？ηθγτ￠8．一
speclmen GK−L
6363speClmen
GK−L
6363L
（mm）
23．2
Lh／L
（％）
69．4
H D La
（mm） （mm） （mm）
18．65 8．45 8．O teeth ribs
numb． numb．
43 29
Lh （mm）
16．1
valve
1eft
H／LI
（％）
80．4
D／L
（％）
36．4
La／L
（％）
34．5
Dθ8￠γ⑳励θア醐α袖8．−The shell is moderately small， inflated and rhomboid with depressedly expallded postero−dorsal part， ol）liquely truncated posterior end，
steeply tapering anterior end and broadly arcuate ventral margin． The umbo is broad， low and distinctly prosogyrate． The posterior flexure is distinct． The surface sculpture consists of 29 ribs which are quadrate in profne with the flat
top and separated by rather deep， narrower and Hat interspaces． The growth
T．SHUTO
lines are fine and close but occasionally distinct． They cross over the ribs七〇 form the且ne crenulations， which are dis七inct on both anterior and posterior parts．
The ligamental area is very narrow， very inequilateral and provided wi七h a few chevron−like grooves at the central part below the beak and wi七h fine horizontal striae at the rest． The hinge teeth consist of shorter anterior row and longer posterior one， which merge with each other at some dis七ance behind the pointed beak． The hinge line is slightly arcuate． The inner margin is heavily crenulated．
Oo勿pα冗80η．−The original author pointed out tha七ノ1γoαgθη（Z67zgαγzθ？z8Z8 is
remarkably variable in the shell form． Some have an eleva七ed umbo and the
others have a Iow one． The present specimen closely resembles the Iatter form except for the ratio of the Iength of the hinge七eeth to the dorsal line， which is smaller on the present specimen than on the Javan fossils．AγcαIo冗6αταREEvE（1844， p1．9， f．58）， which is included in S6αpんαγcαon the basis of larger left valve than the right， is a close ally to A．9θη（ZZ？τ9α？zθγa8￠8 in having the similar outline， inHation and sculpture． They may be treated as conspecific， if the minor difference of the umbo alld sculpture is not evaluated．
K．MARTIN compared his specimens of A． gθ閲仇gα％θ％8 8 with living A．砺ヵZ−
qμα施（LINN面）（1758， P．694；REEvE，1844， P1．9， f．60），but the shell of the latter is much larger， equivalve and provided with more numerous ribs than the former．
Lo6αIZ句．−SKGS−73．
王ro冗zoη8．−Pliocene of Java． Upper part of the Ulian Flormation of Panay．
Subgenus Aπα（1αγα （s． s．）
／1ηα（1αγ．α（ノ1γτα〔》αγ。α）￠αγηbα￠αγzα （MARTIN）
P1．2， Figs．9，11 and 12；P1．3， Figs．14 and 17 and Text−fig．4 1885．
1910．
1924．
∠4γω￠α働bα6耽αMARTIN， Samm1． Geol． Reichs−Mus． Leiden Ser．1， Bd．3，
p．244，Tab．12， f．249．
∠4γ￠α （∠4ηαdαγα）診α仇bαcα働，MARTIN， ibid． N． F． Bd．1， Abt．2， p．367，
Taf．52， fs．88，88a， b， and c．
∠4ηα∂α㌍α￠α仇bα6αηα，CossMANN， Jour． d． Conchy1． Tom．68， P．94， P1．4，
fs．11 and 12．
Mατθ冗α1．−GK−1、6592 （right），6593（conjoined）and 5494 （lef七）
SKGS−71 and GK−L 7056（conjoined）from loc． SKGS−72．
from loc．
ハzθα8％γθ勿θ励8．一
m ㎝ 品 236
K 0
59 59 05
㏄ G667
S
註 ㍑砺 ㎝
㏄ G667
S
L
（mm）
23．45 14．2 21．25 1、h／L （％）
69．1 75．0 70．4
H
（mm）
16．9 10．35 14．45
teeth numb．
47 39 47
D
（mm）
7．7 4．35 6．65
1、a
（mm）
8．2 5．45 7．15 ribs numb．
24 23 24
Lh
（mm）16．2 10．65 14．95
valve
R
L（conj．）
R（conj．）
H／1二
（％）
72．1 72．9 68．0
D／LI
（％）
32．8 30．6 31．3
1、a／L
（％）
35．0 38．4 33．6
4
へ
∠
一
27
Fig．4 0n some morphologic features of taxodont species from Pallay．
1−7・4ηαdαγα（・4πα∂αγα）￠醐bα6αηα（MARTIN）
1：ligamental area of conjoined valves， GK−L 6593．2：七〇p view of the same specimen as the preceding．3：ligamental area of right valve， GK−L 6592．4：1igamental area and post larval shell of sessile stage， right valve， GK−L 7495． 5−7： serial change of the profile of the radial ribs of central part through growth stages， GK−L 7492．
8−12 Aηαdαγα（ノ1ηα∂αγα）τθημg仇θα（REEVE）
8：Iigamental area of right valve， GK−L 7055．9：1igamental area of right valve， GK−L 7453．10−12：rib−form a七the distal margin on anterior（10）， mid−ventra1（11）and posterior part（12）， GK−L 7055．
13−15 、4ηα∂αγαsp． GK−1」6672．
13：1igamental area and post−1arvel she11．14：prome of ril）s at mid−ventral margin．15：details of the rib morphology．
16−20： Aγτα（1αγα（ノ1γταdαγα）1μzoγzづ6αp￠θ灼？ηo㌍pんαsubsp． nov．
16：1igamental area of right valve， GK−L 6713．17：1igamental area of left valve， GK−1」6712． 18−20： profile of ril）s at posterior（18），
main（19）and anterior part（20）．
21−22 21：
22：
23−25 23：
25：
26−27 26：
∠4ηαdαγα（Aηαdα㌍α）加γπθ8元（D，ARcHIAc et HAIME）
ligamental area and post larvel shell of left valve， GI（−L 6634．
profile of ribs of the same specimen as the preceding．
Mθ1αoθ仇αθα匁θc￠仇げoγ働i8（LAMARCIO
cardinal area of GK−L 6680．24：profile of ribs of GK−LI 6680．
profile of the ribs of GI（−L 6677．
∠1πα∂αγα（Aηαdαゲα）（況￠みo￠αmα（DESHAYES）
1igamental area of left valve， GK−L 7710．27：detailed morpho一 10gy of ribs of the same specimen as the preceding．
28−30 Aηαdαγα（Soαpみαγcα）gθγτ（1仇gαηθπ8i8（MARTIN）
28：1igamental area of left valve， GK−L、6363．29−30：pro丘1e of ribs at posterior（29）and anterior part（30）．
Unit bar a represents lmm for 5−7 and 27， bar b does 3mm for 1，
4，10−26，29and 30 and 6 mm for 2，3，8，9and 28．
T．SHUTO
1）θ8励p励θγ醐α袖8．−The shell is rhomboid−orbicular， medium in size，
equivalve， inequilateral and infiated． The umbo is large， moderately elevated，
prosogyrate and incurved and leans to the anterior． The beaks are remote from
each other． The anterior and posterior ends are obliquely truncated forming blunt angles with the dorsal margin respectively． The antero−ventral and
postero−ven七ral margins are regularly rounded to continue to the weakly arcuate ventral margin． The posterior Hexure is weak． The sculpture consists of about24ribs and七he distinct growth lines． The ribs are roof−shaped separated by
similarly reverted roof−shaped interspaces at血rst， then the ribs become Hat at the七〇p， while the interspaces keep the original form． Finally七he ribs are bi−partite at the top with a shallow furrow between and the interspaces become
round at the bottom． The dis七inct crenulations are formed at the cros・sings of the concentric lines and the top of the ribs wi七h the exception of the weak ones at the anterior and posterior ends until the adolescen七stage． The deterioration of the crenulation seems to be an adult feature of七he species． The cardinal area is moderately wide and inequilateral． The shorter and broader anterior half is free from the ligament and the posterior half， occupying about 60 percent of the hinge Iength， is separated from七he anterior half by an oblique groove immediately below the beak and has a few grooves． The hinge line is almost straight and discontinuous in七errupted by the apparent discordance just behind the beak． The anterior row is much shorter than the posterior one and situated slightly apart from the very margin． While the teeth of七he posterior half are in line with the very margin and visible from outside when the ligament is removed（Pl．2，Fig．11）．
Co物pαγ680η．−The present specimens are easily identi6ed七〇Aグ6α￠α働bα6αηα MARTIN by the typical characters of the ribs， she11−form and cardinal area．
Lo6α協ゼθ8．−SKGS−71 and 72．
Ho冗20η8．−Upper Miocene and Pliocene of Indonesia． Upper part of the
Ulian Formation and the Cabatuan Formation of Panay．
ノ1ηα∂αγα（A？zα肋γα）（1661乞o加働α（DESHAYES）
Pl．3， Figs．1，2，3，7，9and 15 and Text−fig．4
1863．
1885．
1891．
1907．
1909．
1920．
1935．
、4γoα（臨んo加働αDEsHAYEs， Conchy1． de l，ile de la R6union（Bourbon）P・22，
p1．3， fs．18 and 19．
．4γ6α8仇gμZα弼8MARTIN， Samml． Geol． Reichs−Mus． Leiden Ser．1， Bd．3，
p．247，p1．13， f．252．
Aγoα（Bαγbα碗α2）（旋1Lo亡αηLα， KoBELT in MARTINI and CHEMNITz， Conch・
Cab． Bd．8， Abt．2， p．29， pl．8， fs．7and 8．
∠4γ￠α∂α，砿2θ励θγgτLAMY， Jour． de Conchyl． Tom．55， p．232， pl．3， fs．9−11．
∠4γ6α（S￠αpんαγ6α）砺6みo￠oMαg併α励8αLYNGE， Mem． Acad． Roy． Sci． et Lettr． Danemark． Ser．7， Sec． Sci．， Tom．5， No．3， p．125（29）， pl．2， fs．3 and 4．
∠4γ￠α （／1舵α∂αグα）8仇9視1α碗8，TEscH， Pa150nt． v． Timor， Lief・8， P・93，
pl．137， fs．250a and 250b．
MαbθZIαγcα ∂α，％たθπbθγ9τ， IREDAE， Great Barrier Reef Exp・Sci・Rep・
Vo1．5， No．6， Mollusca P，t．1， p．265， p1．2， fs．13 and 13a．
Mα￡θ冗αZ．−GK−L 6673，6674，6710 and 6711 from one and the same locality．
1レfθα8％γθ？ηθ？Z彦8．一
エ
speclmen GK−L
6673 6710 6711ロ
speClmen GK−L
6673 6710 6711
（mm）
13．5 11．1 10．O Lh／L （％）
69．4 67．0
H
（mm）
9．4 7．6 7．0
D
（mm）
4．3 3．25 3．0
teeth numb．
0ワ・
43
La
（mm）
3．75 2．75 2．75 ribs numb．
26 19 21
Lh （mm）
7．7 6．7
valve
LLR
H／L
（％）
69．6 68．5 70．0
D／L
（％）
31．9 29．3 30．0
La／L
（％）
27．8 24．8 27．5
Z）θ86㌍⑳励￠グθ仇α袖8．−The shell is small， moderately in且ated， remarkably
inequilateral with an anteriorly leaning umbo and elliptical with smoothIy roullded margin excep七for rather straight dorsal side． The posterior part is
compressed and devoid of the distinct Hexure． The umbo is broad and moderately elevated above the dorsal line． The antero−dorsal angle is sharp． The ribs arevariable in number counted by 20−26， as wide as the deep interspaces and
beautifully granulated at七he crossings of the concentric lines． The most char−acteristic feature of the ribs is the pattern of the development of their granules．
The granules are in a single row on七he juvenile part of七he ribs． While each rib is gradually bipartited by七he median s｝1allow groove and consequently the
granules are drawn up in two rows． The inner surface is distinctly costate
correspondingly to tlle sculp七ure on the outer surface． The cardinal area is moder−ately wide， extremely inequilateral， somewhat curved up七〇the posterior rim and
almost smooth except for weak llorizontal striae． The llinge七eeth are dis−
continuous separated by a narrow too七h−free area． The anterior row is about ahalf as Iong as the posterior one．
Co物pαが80η．−The present specimens are featured by七he elliptical shell with dicllotomous ribs． Aγ6α砺oんo舌o仇αDEsHAYEs（1863， p．22， pl．3， fs．18 and 19），
ノ1．8乞γzg秘1α冗8 MARTIN （1885， P．247， pl．13， f．252） and A．∂α％花θηbθγ9づ LA］MY
（1907，p．232， pl．3， fs．9−11）are close allies to七he present specimens．．Aアcα 砺6んo￠o仇αis， according to the original author， provided with sllarp posterior
Hexure， where about four ribs are not bifurcated． While LYNGE described七hat
the mentioned characteristic is not constant but variable among the specimens．If this is 七rue， one can hardly 6nd out七he basic difference to separate three named taxa． Hence it should be reasonable to trea七them as conspec姐c． Aγ￠α 8仇gμ1αゲ68MARTIN seems to be ra七her variable in morphology especially in shell−
form． Aγ￠α碗￠んo渉o㎜（especially forma∂αμ鋤ηbθゲ9のvery closely rese㎞bles A．8仇g％Zα惚，especially to the specimens from the Pliocene of Timor reported by TEsCH （1920， p．93， pl．137， fs．250a and 250b）． The difference is o111y in七hat the former， in general， has longitudinally longer granules than tlle latter． The
present fossil specimens examplify a remarkable variation concerning the last
mentioned point indicating that the character is invalid as a criterion for speci6c separation．T．SHUTO
Lo￠α1 勿．−SKGS−74．
HoγZzoη8．−Pliocene of Timor and Seram and Recent in Sou七heast Asian waters to North Australia． Upper part of the Dingle Formation in Panay．
Aηα∂αγα（A％α∂αγα）アθγγ秘g仇θα（REEVE）
Pl．2， Figs．10，13，15 and 16 and Text−fig．4 1844．
1844．
1910．
1920．
∠レ6α∫θγγμg仇θαRE面vE， Proc． Zool． Soc． London p．43．
、Aγcα∫θγwg仇θα， REEvE， Conch． Icon． Vol．2，∠4γoα， pl．6， f．39．
∠4γ6α（．4ηαdαγα）∫θγwgiηθα， MARTIN， Samml． Geol． Reichs−Mus． Leiden N．F． Bd．1， Abt．2， p．366， Taf．52， f．85．
∠4γoα （∠4πα∂αγα）∫θγwgZ舵θα， TEscH， Pal50nt． v． Timor， Lief．8， p．93，
Taf．138， f．251．
五fα￠θγ鋤．−GK−L 6364 （left， immature）
（right）from loc． SKGS−72 and GK−L 7453
postero−ventral part）from loc． SKGS−71．from loc． SKGS−73， GK−L 7055
（conjoined， slightly broken at the
1》fθα82δゲθ？ηθ？z￠8・．一
コ
speclmen GK−L
6364 7055 7453 サ
speclmen
GK−L
6364 7055 7453
L
（mm）
23．05 29．6 37．6
Lh／L
（％）
67．7 75．3 76．6
H
（mm）16．9 20．5 27．8
D （mm）
7．75 10．25 12．5
∠u
（degrees）
140．4 136．1 149．2
La
（mm）6．6 9．3 13．4 teeth numb．
46
45
（mm）
Lh
15．6 22．3 28．8 ribs numb．
而
b方り6
0乙9一9一
H／L
（％）
73．3 69．3 73．9
valve
LRR
D／L
（％）
33．6 34．6 33．2
La／L
（％）
28．6 31．4 35．6
1）θ8cがpf初θゲθ勿α袖8．−The shell is equivalve， medium in size， rather solid，
very inflated， ovoid and inequilateral with longer posterior part七han the anterior．
The umbo is large and elevated above the dorsal line． The posterior七runcation
is oblique with a marked sinus immediately below the postero−dorsal corller．
The posterior flexure is distinct． The surface is sculptured by regularly spaced ribs and distinct growth lines． The ribs are七riangular with granular crenula−
tion on the top at七he early growth stage． Thereafter the ribs are widened
gradually to show quadrate prome and finally they have a slight depression on 七he top． In keeping pace with the widening of the ribs the crenulation l）ecomes weak to illustrate very fine crenules at the both sides of the七〇p of each rib． On the median depression of the ribs the grow七h lines are not so strong． The ribs are as wide as or wider than the interspaces on the main and pos七erior surfaces，while they are narrower on七he anterior． The inner margin is coarsely crenula七e．
The cardinal area is wide and inequilateral wi七h shorter and wider anterior par七and Ionger and narrower posterior part． The ligamental area is triangular
with Iigament−free area on the anterior vicinity． The ligament−free area is
rather wide occupying more than 30 percent of the cardial area unti1七he adoles−cent stage， but it becomes abruptly small occupying only 20 percent of the area at the adult stage． The chevron−like grooves are developed on wllole ligamelltal
