ISSN 0031-0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New Series

No.

176

Pa laeontologica l Society of J a pan
December 30, 1994

Co-Editors

Tsunemasa Saito and Kei Mori

Language Editor

Martin Janal (New York)

Editorial Board
Shiro H asegawa (Hokkaido U niversity), Kunihiro lshi zaki (Tohoku University), Tomoki K ase(National Science Mu seum) , Toshiaki Maruyama (Yamaga ta Un iversity), Kei Mori (T o hok u Un iver sity), Kenshiro Ogasawara (Uni versit y of Tsukub a), Tsunem asa Saito (Tohoku Univers ity) , Yokichi T akaya nagi (Ishin omaki Senshu University) , Kazushige Tanabe (Uni versity ofTokyo) , Yukimitsu Tomida (Nat iona l Science Museum ), Kaz uhik o Uemura (Na ti ona l Science Museum) , Akira Yao(Osaka C ity U n iversity)

Officers for 1993- 1994
President: Hisayoshi 19o
Honorary President: Teiichi Kob ayashi
Co un ci llors : Kiyotaka C hinzei , T akashi H amad a, Yoshikazu Hasegawa, Ita ru H ayami ,Hiromichi Hirano , Hi sayoshi Igo , Noriyuki Ikeya, Junji Itoigawa, Tomoki
K ase, Makoto Kato, Tatsuaki Kimura, Itaru Koizumi, Kei Mori , Hiroshi Noda,
Ikuwo Ob ata, Ken shiro Ogasawara, Tomo wo Ozawa, T sunem asa Saito, Yokichi
Takaya nagi, Kazushige T anabe, Akira Yao
Members o f Standing Co mmittee : Kenshiro Ogasawara (Genera l Affa irs), Tomoki K ase(Finance), Tsunem asa Saito (Ed itor in Chief, TPPSJ) , Kei Mori (Co -Editor, TPPSJ),
Kazushige Tan a be (P lan nin g) , Hiroshi Nod a (Membership ; C o-Edito r, Specia l Papers),
Hiromichi Hirano (Foreign Affa irs), Itaru H aya mi , Toshiy uki Yamaguchi (Edi to rs," Fossils"), Juichi Yanagida (Co-Editor, Special Papers) , T ats ua ki Kimura (Friend s of
Fossil s)

Secretaries: K ats umi Ueno , Shuko Adachi (Genera l Affa irs) , Masanori Shimamoto (Editoria lof TPPSJ), Akira Tsukagoshi (Plann in g) , K atsuo Sas hida (Members hip), Tatsuo Oji(Editori a l of " Fossil s") , T akeshi Ishib as hi , Akihiko Matsukuma (Ed it oria l of Special
Papers), T amiko Oh ana (Friend s of Foss il s)
Auditor: Hisaharu Igo
The fossil on the cover I S Isocrinus (Chladocrinus ) hanaii Oji , an Early Cretaceous(Aptian) crinoid, which was described from the Hiraiga Formation exposed at H ai pe,
T anoh ata-mura, Shimo-Hei County, Iwate Prefecture, Northeast Japan . (University
Museum of the University of Tok yo colI. cat. no. ME6950, paratype specimen, length
about II cm)

All communication relating to thi s journal should be addressed to the

PALAEONTOLOGICAL SOCIETY OF JAPAN
c/o Business Cen ter for Academic Societies,
Honkomagome 5- 16- 9, Bunkyo-ku, Tokyo 113, Japan

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 176, pp. 591-617, 16 Figs., December 30, 1994

977.

KOIZUMIA YANAGISAWA GEN. NOV., A NEW MARINEFOSSIL ARAPHID DIATOM GENUS*
YUKIO Y ANAGISA WA
Geology Department, Geological Survey of Japan,
1-1-3 Higashi, Tsukuba, Ibaraki, 305

Abstract. A new marine fossil araphid diatom genus Koizumia is established toreceive three species, Koizumia tatsunokuchiensis (Koizumi) Yanagisawa comb. nov. (originally described as Rhaphoneis tatsllnokuchiensis by Koizumi, 1972), K. adaroi (Azpeitia)
Yanagisawa comb. nov. (originally described as Cymatosira adaroi by Azpeitia, 1911), andK. akibae Yanagisawa sp. nov. Detailed morphologies of the genus are presented with its
precise stratigraphic and geographic distributions. The genus is characterized by crib rumlike siliceous layers across the pores of marginal ridge, the suture line on the marginal ridge
and the presence of transapical and longitudinal rows of areolae on the valve face. The
three features are unique to the genus and have never been observed in its related genera
Rossiella Desikachary et Maheshwari and Bogorovia Jouse. KoizlImia is typically neritic in
distribution mainly in near-shore or upwelling regions of the middle latitudes, and issignificantly different from Rossieffa and Bogorovia, both of which have essentially an
oceanic and tropical to sUbtropical distribution. Both the morphological uniqueness andthe differing geographic distribution pattern are considered to be distinctive enough to form
the basis of a new generic erection of Koizllmia. The genus has a rimoportula in the patternof "one per cell" with an apical pore field at each apex, and forms a long colony chain
connected by marginal ridges. These features suggest that the genus can be placed in thefamily Cymatosiraceae Hasle, von Stosch et Syvertsen.
Key words.

Diatom, fossil, marine, morphology, stratigraphy, Koizumia

The current study was prompted by theneed to reveal the morphology and precise
stratigraphic ranges of the two araphid
diatom genera Rossiella Desikachary et Maheshwari 1958 and Bogorovia louse 1973 inorder to build a firm basis for the taxonomyof the two genera. The two diatom genera
share many common features and constitutean important fossil diatom group. Although
the two genera were both monotypic whenerected, subsequent studies have added many
new members by descriptions of new species
and generic transfers, some of which are ofgreat importance in Paleogene and Neogene
diatom marine biostratigraphies (e.g. Fenner,
1985; Barron, 1985). Recently, Gersondeand Schrader (l984) and Desikachary et al.

Introduction

During the past three decades, taxonomy ofmarine fossil diatoms has greatly improved
through steady accumulation of knowledge
on morphology revealed by scanning electron
microscopy along with advanced diatom biostratigraphy using well preserved and welldated materials provided by deep sea coring
projects. However, many fossil diatoms
have not been examined in detail from taxonomic view point, and therefore the taxonomy of fossil diatoms still remains largely
incomplete.
'Received July 22,1994; revised manuscript accepted
October 21, 1994
591

Yukio Yanagisawa

592(1984) clarified the taxonomy of the twogenera. More recently, Fourtanier (1987)
made a detailed taxonomic revision on almost
all species known then, demonstrating theirstratigraphic and paleoceanographic value.
She also first examined some species by scanning electron microscopy to reveal the uniquestructure of the genera, and proposed an
evolutionary lineage for some members.
However, the whole evolutionary lineage ofthis diatom group has been still unknown.
As a result of my investigations of the twogenera, I came to the conclusion that thediatom group can be clearly subdivided into
three distinct units which are significantly
different from each other in both morphology
and geographic distribution, and that theseunits should be treated as three separate genera, i.e. Rossiella Desikachary et Maheshwari,
Bogorovia Jouse and Koizumia Yanagisawa
gen, nov.
In this paper, the new genus Koizumia isdefined to receive three species, Koizumia
tatsunokuchiensis (Koizumi) Yanagisawacomb. nov (originally described as Rhaphoneis tatsunokuchiensis by Koizumi, 1972),
K. adaroi (Azpeitia) Yanagisawa comb. nov.
(originally described as Cymatosira adaroi
by Azpeitia, 1911) and K. akibae Yanagisaw a sp. nov. The morphology of eachspecies is described on the basis of detailed
light and scanning electron microscopic
observations. The stratigraphic ranges of theTable 1.

three species based on the analysis of DSDP
Hole 438A off Japan and their geographic
distributions surveyed 1D literature arepresented.
Redefined descriptions of the genera Rossie/la and Bogorovia will be provided in separate papers (Yanagisawa, in prep. a, b), andphylogenetic and evolutionary relationships
between the three genera will be discussed ina later paper (Yanagisawa, in prep. c).
Material and methods
For biostratigraphic study, samples fromthe Lower Miocene through Quaternary section of DSDP Hole 438A were analyzed(Table I). Hole 438A is located in thenorthwestern Pacific, off northeast Honshu,
Japan, and contains an almost complete reference section for Lower Miocene throughQuaterenary North Pacific diatom biostratigraphy (Barron, 1980; Akiba et al., 1982;
Maruyama, 1984; Koizumi, 1985; Oda,
1986; Akiba, 1986). In this study, the slides
analyzed by Akiba et al. (1982), Maruyama(1984) and Akiba (1986), together with theslides deposited in DSDP Reference Center in
National Science Museum (Tokyo) were reexamined with special attention to the genus
Koizumia. For taxonomic study and detailed scanning electron microscopy (SEM),
several selected samples were also used (TableI).

Cores and samples used in this study.

No.

Cores & samples

Area

Location

Fonnation

References and remarks

I

DSDP Hole 438A

Northwest Pacific

40°37.79' N, 143°14.15' E

DSDP core

Scientific Party (I 980)

2

A-I

Tomioka, Fukushima, Japan37"20.26' N, 140°59.31' E

Drill core

Yanagisawa et aI. (I 989)

3

D-lSunda Forearc, Java

9°45.57' S, I II °36.68' E

Dredge sample

Yanagisawa (I 987)

4

IDS 8842

San Felipe, Baja California

31° 8.89' N, 115° 1.48' W

Upper Miocene

coIl. by Mr. N. Ogura

5

M32

Ajigaura, Ibaraki, Japan

36°22.82' N, 140°37.42' E

Isozaki F.

Maruyama (I 984)

6

Ya 185

Matsushima, Miyagi, Japan

38°28.78' N, 141 °11.45' E

Tatsunokuchi F.

Akiba et aI. (1982)

7

Mzn09

Mizunami, Gifu, Japan

35°23.71' N, 137°14.66' E

OidawaraF.

Yanagisawa (1993)

8

Nmy I3A

Sumon, Niigata, Japan

37°22.1 I' N, 139°02.04' E

NishimyoF.

Yanagisawa et aI. (I986)

9

Ha67 (Se 40)

Iwanuma, Miyagi, Japan

38°06.59' N, 140°50.56' E

Tatsunokuchi F.

Yanagisawa (1990a)

10

Km09

Kamogawa, Chiba, Japan

35°03.56' N, 140°05.04' E

Nabuto F.

coIl. by Y. Yanagisawa

977.

Diatom genus Koizumia

The samples were prepared following themethod of Koizumi and Tanimura (1985) or
Maruyama (1984). A strewn slide for lightmicroscopy (LM) was prepared for each sample on an 18 X 18 mm cover glass andmounted in Pleurax on a glass slide.
One hundred diatom valves were counted
for each sample at X 1,000 magnification,
following the counting criteria of Schrader
and Gersonde (1978). After the counting,the entire slide was examined to record thepresence of species missed in the counting.
Estimate of the quality of diatom preservation was generally subjective. An Olympus
BH-2 light microscope was used in this study.
For SEM observation, samples were prepared following Akiba and Yanagisawa (1986).
The samples used for SEM were processed bynearly the same method of LM examination,
but clay minerals were removed completelyby the decantation with 0.01 N sodium pyrophosphate (Na 2 P 2 0 7 ) (at least 10 times).
Using a micropipette, 0.5 ml of the suspended
sample was placed on a slide glass, and driedon a hot plate at 60°C. Using a tiny paintbrush, diatom valves of good preservation
were picked up from the slide glass under thelight microscope at X 100 magnification andmounted in a small tip of cover glass. The
tip was then put on a sample stage. SEM
observation was carried out using HITACHI
S-405 scanning electron microscopes at Osaka
University and the Geological Survey ofJapan.
Some dimensions such as length, width, thenumber of transapical costae and number ofareolae per 10,um were measured from LM
photomicrographs in order to reveal metric
relationship between these parameters.
Results
Morphologic terminology for description

For description of the genera Koizumia,
Bogorovia and Rossiella, morphologic terminology common to the three genera is
introduced in this section. General mor-

593

ap

pm

51

Figure 1. Colony chain of Koizumia akibae
Yanagisawa sp. nov. Note the fusion of sibling
valves. a: areola, or: external pore of rimoportula, r: inner aperture opening of rimoportula, i:
inner surface of valve face, Ic: longitudinal costa,
tc: transapical costa, ap: apical pore field, pm:
pore of marginal ridge, sl: suture line formed byfusion of sibling valves, sv: separation valve, c:cingulum, ps: pair of sibling valves, f: frustule, mr :marginal ridge.

phologic terms follow Anonymous (1975),
Ross et at. (1979), Simonsen (1979) andRound et at. (1990).
Figure I illustrates the part of a colony
chain of Koizumia akibae, showing the basic
structure of the genus. The valve outline of
the three gene~a is basically linear-Ianceolatewith more or less rostrate apices. At each
apex there is an apical pore field (ap) consisting of fine puncta.
Marginal ridge (mr) is a continuous ridge
between the valve face and the valve mantle,
and is the most important structure that characterizes the three genera. All members of
the genera Koizumia, Rossiella and Bogorovia
have marginal ridges on both margins without exception. Four types of marginal ridges
are recognized (Figure 2). Type I IS aseparate-type marginal ridge with a single
longitudinal row of pores. This type has

Yukio Yanagisawa594

been observed in Rossiella elongata (Barron)
Desikachary (Figure 3-1) and R. paleacea(Grunow) Desikachary et Maheshwari. The
remaining three are of fused types where themarginal ridges of two sibling valves arecompletely fused so that a pair of fused si bling valves (ps) seems as if it were a single
frustule. Type 2 marginal ridge has two longitudinal rows of pores. This type has beenreported in Bogorovia praepaleacea(Schrader) Jouse (Fourtanier, 1987) . Type 3
is a fused-type margin al ridge with three lon-

Singleval ve - - 0000000000000000000000000

<r. /

Q)

Type 1

ggg8goooo8~ogo88088ggg Type 2
0000

00

0

0

>

~

>

01)

t:

Type 3

Type 4
Figure 2. Types of marginal ridge in the genera
Koizumia, Bogorovia a nd Rossiella.

gitudinal rows of pores . Bogorovia
veniamini Jouse is characterized by thi s typeof margi nal ridge (Figures 3-2, 3- 3). Type 4
marginal ridge with two rows of pores isapparently similar to type 2, but clearly di stinguished by having a cribrum-like siliceous
layer across the pore (Figure 14- 8) and a faintsuture line between the rows of pores (denoted as " sl" in Figure I ; Figure 14-9). The
cribrum-like layer is perforated by regularly
arra nged minute pores, showing virtu a lresemblance to the cribrum. The layer isthin an d delicate so that it might be easily
di sso lved or detached in poorly preserved
specimens, leaving only several short connecting bars around the inner margin of the pore
(Figures 12 - 7, 14- 5). Thi s cribrum-likelayer is unique to the type 4 margi nal ridge,
and has never been observed in the othertypes of margi nal ridges. The type 4 appears,
therefore, to be distinct from the other three
types of marginal ridges.
The spacing of pores of margi nal ridge
almost equals that oftransapical costae in thefused-type margin a l ridges (types 2, 3 and 4).
In the separated-type marginal ridge (type I) ,the spac ing of the pores is nearl y equal to thespac ing of margi nal areolae on the valve face.
Species wi th the fused-type marginal ridges
may form a long chain colony by the fusion

Figure 3: SEM photomicrographs of marginal ridges of Rossiella a nd Bogorovia. Scale bars equal
10 Jim for Figs. 3- 1, 3- 3, and 5 Jim for Fig. 3- 2, respectively. 1. Type I marginal ridge of Rossiellaelongata (Barron) Deslkachary ; Sample M32, Isozaki Formation, Ajigaura, Ibaraki , Japan. 2, 3. Type
3 marginal rIdge of Bogorovia veniamini Jouse; Sample RC 12- 65 , 1,065 cm.

977.

Diatom genus Koizumia

A : Subcentral

B : ApicalA

C : Central
B

C

Figure 4. Location of rimoportula in the genera Koizumia. Bogorovia and Rossiella.

K. adaroi

K. latsunokuchiensis

I
Figure S. Morphology of the three species in
the genus Koizumia. Figs. la, 2a and 3a show theLM images of K. adaroi (Azpeitia) Yanagisawacomb. nov., K. tatsunokuchiensis (Koizumi)
Yanagisawa comb. nov. and K. akibae Yanagisawa
sp. nov., respectively. Figs. I b, 2b and 3b are theschematic drawings demonstrating transapical andlongitudinal costae.

of their marginal ridges (Figure 1). Fourtanier (1987) reported a relatively long chainof Koizumia adaroi composed of seven frustules (Fourtanier, 1987, pI. 16, fig. 5). I havealso observed short chains consisting of twoor three sets of fused sibling valves (Figures
12-5,14-3). On the contrary, the species
with the separate-type marginal ridge may besolitary.
Transapical costae (tc) which extend fromboth valve margins are present in some members of the three genera (Figure 1). For

595

description, the spacing of the transapicalcostae is classified into two categories; narrowly spaced type (9-14 costae in 10 ,urn) andbroadly spaced type (6-8.5 costae in 10 ,urn).
An additional longitudinal costa (lc) parallelto the side is present only in K. akibae (Figure I).
A rimoportula(r) is present generally in"one per cell pattern"; a frustule consists of aprocess valve and a non-process valve, andthus the frustule is heterovalvate. Threepatterns of location of the rimoportula arerecognized; subcentral, apical and central
pOSItIOns (Figure 4). The species whichmake a colony chain by their fusion of
marginal ridges (types 2, 3 and 4) have a subcentral rimoportula without exception. The
subcentral rimoportula has an external pore(or) on the marginal ridge (Figure 1 ; Figures
12-3, 14-6). This is probably because theprocess may function to communicate some
substance between the cell interior and theexternal environment. If the rimoportula ofa valve with the fused-type marginal ridge
would open on the valve face, it could notfunction as the pathway of chemical matter,because its outer opening does not lead to theexternal space. The apical and central positions of rimoportula are observed only insome species of Rossiella which have theseparated-type marginal ridges (type 1).
The areolae of the genera Koizumia, Bogorovia and Rossiella show a wide range ofvariation in size. The size of areolae isclassified into five ranks for description:coarse (ca. 1.2-1.5,um in diameter), medium(ca. 0.8,um in diameter), fine (ca. 0.4-0.5,um
in diameter), very fine areolae (less than 0.1,urn in diameter) and the absence of areolae(hyaline). The coarse areolae are polygonalin shape and compactly packed. The
medium to very fine areolae are circular inshape and distributed sparsely and randomly
in some species, but in Koizumia, they arearranged in transapical and longitudinal rows
(Figure 5).
The cingulum (c) may be composed of

Yukio Yanagisawa596

some bands, but its detailed structure andcomposition are not known at present.
At the end of a colony chain, there is aseparation valve (sv), a special valve thatshows a different morphology from other
Table 2.

vegetative valves and functions to separate along chain into short chains of suitable length(Figure 1).

Occurrence of Koizumia species in DSDP Hole 438A.

Diatom zones after Akiba (1986) .

.
Diatom zones

g

Q

~

IE u

N.Otklllicuia
kmIIIschlJlica

78

·a

i!

ThD/Qssionema 68
schraderi

.~

6 ·1

18 -22

G

A

11 -6

20 -24GA~".~ "-

Diatom zones

~
.~
l:!

~ ~ ·'"1~

10 -11
20-24

R

19 -23

G

A

G

A

-

23 -1

10 -14

G

A

24 -3

10 -12

G

A

26 -4

10 -14

G

A

F

26 -6

15 -19

G

A

R

27 -4

20 -24

G

A

R

28 -2

20 -24

M

A

R

Denticulopsis

29 -2

20 -24

M

A

C

lralay_-16 -20

51 -4

16 -20

51 -6

16 -2052 -3

36 -38G

52 -4

36 -38

G

A

53 -1

77 -81

GR

54 -1 .110 -114

R

55 -1

A

34 -1

22 -24

M

C

-

35 -3

24 -28

M

A

36 -1

32 -36MC- R- - R - - F

45 -49MA

30 -34

G

A

G

A

G

A

.

Tha/assione,"" 68schraderi

- - -

A

R

Denticulopsis

R

dimorpha

5D

- R -

R

- R
R
- - R - - - R - - - R - R- R- - R - R - - - R- - R - R - R - - R - - - R R - - - R - - - - - - - R - - - R - - - R - - - - - - -55 -3

70 -7460 -62GA

57 -1 • 115 - 117
57 -2
31 -35

P

C

G

A

57 -3

31 -35

M

R

57 -4

59 -61

GA
R

R

16 -20

P
P

R

59 -5

17 -21

G

C

62 -1

A

P

R

16 -20

M

C

R

43 -1

59 -63

P

R

R

43 -6

82 -86

M

R

R

44 -1

60-64

M

R

R

-

Denticulopsis

44 -3

10 -14

M

R

R

- -

praedimorpha

47 -1

10 -14

M

F

48 -1

14 -18

M

R

R

48 -3
49 -3

46 -SO

M

A

10 -14

R

49 -6

10 -14PP- R R - - - RRR- - - -

T.yabei

5C

58

F
R

A
R

56 -3

-

C. lIicobarica

SA

R

DelilicWopsis
hya/ina48

20 -24G

63 -1 • 110 - 112
64 -1
10 -14

P

F

G

A

64 -3

10 -14

G

A

64 -5

30 -32

G

A

65 -1

54 -56

M

R

65 -7

17 -18

P

R

66 -2

82 -84

G

A

67 -1

27 -32GA

67 -1 • 112 - 113
68 -1 • 101 -103

G

A

P

A

69CC

G

A

R

-

G

17 -21100 -101

R

A

F

A

59 -4

42 -6

-

- - R
- - F - - - F - - - R - F - - - R - - - R
R - - - R

A

58 -1

42 -5

- R -

C

F

73 -74!I' 10::~RPP

70 -74

F

.!

C

R

42 -4

R

6A

C

-

A

10 -11

G

A

C

51 -1

G

C

- -

SO -7

20 -24

G

- -

R

P
P
P
P
P
P

120 -124

MR

20 -2431 -1

10 -14

P
P

20-24

33 -1

20 -24

..

50 -3

- F
R -

"~

~ :.: :.:

SO -6

R

l

<

.!!.

SO -1

20 -2437 -3

j. ~ ] -I"·1 1 I ~
e j j

49 -7

13 -3

40 -2

:~ j~

.~

F

21 -3

-

"iii

R

-

41 CC
7A

]

.~ 2

<

.!!.

'"

41 -3

Rowcia. ~.~3." j e j j
1I~ :.: :.: .~
"iii

8

41 -1

caii/ornica

.~

.

j

F

-

R

R

R

R

Preservation: G=good, M=moderate, P=poor. Abundance: A=abundant, C=common, F=few,
R=rare. Abundance of each species: A=abundant (>8%), C=common (5-7%), F=few (2-4%), R=
rare « 1%). • Bogorovia puncticulata Yanagisawa MS will be described in Yanagisawa (in prep. b).

977.

Diatom genus Koizumia

597

Morphology of the genus Koizumia

The valve outline of this genus is linearlanceolate with slightly rostrate apices (Figure 5). Each apex carries an apical pore field
consisting of fine puncta (Figure 12-5). The
transapical costae which extend from both
valve margins are nearly continuous in K.
akibae, but they are discontinuous, interrupted broken lines in K. adaroi and K.
tatsunokuchiensis. Koizumia akibae has anadditional longitudinal costa running along
one side of the margin. The valve face ismore or less convex, and perforated withareolae. The areolae are arrenged in transapical rows between each two transapicalcostae and also form longitudinal rows.
Each areola might be occluded with a meshlike cribrum, but the cribrum is completely
dissolved in specimens observed. The marginal ridge is of type 4 with two longitudinalrows of pores occluded by the cribrum-likesiliceous layers. The cingulum is composedof a few bands with a row of small puncta(Figure 12-6, 14-4), but its detailed composition is not known at present.

Stratigraphic
occurrence

Diatom zones

Neodenticula
kamrschatica

7B

Thalassionema
schraderi

6B

Denriculopsis
knrayamae

6A

Denriculopsis
dimorpha

5D

Thalassiosira
yabei

5C

Stratigraphic distribution

The stratigraphic occurrence of Koizumia
species is presented in Table 2 and Figure 6
for DSDP Hole 438A. The biostratigraphic
zonation is based on Akiba (1986).
The stratigraphic ranges of Koizumia
species are shown in Figure 7, which is mainly based on Figure 6, as well as on some otherimportant biostratigraphic studies such as
Schrader (1973, 1974a, 1974b, 1976), Barron
1980, 1981a, 1981b, 1985, 1992), Fenner(1984a, 1984b, 1985), Koizumi (1985, 1992),
Koizumi and Tanimura (1985), Akiba (1986),
Fourtanier (1987), Yanagisawa (1987) and
Boden (1992). Correlation to the time scaleof Berggren et al. (1985) is adjusted throughBarron et al. (1985) and Oda (1986).
Geographic distribution

The geographic distribution of each Koizumia species was surveyed from the 1itera-

g
80
~

~

g
<1)

g
Denticulopsis
hya/ina

4B

~
~

"0
"0

Denticulopsis
laura

Figure 6.

Stratigraphic

4A~

distribution of KoEach dot indicates the presence of each species. Original data arepresented in Table 2. Stratigraphic range of Rossieffa pafeacea (Grunow) Desikachary et Maheshwari
and Bogorovia puncticufata Yanagisawa MS arepresented as well. The latter species will be described in a separate paper (Yanagisawa, in prep. b).
izumia species in DSDP Hole 438A.

Yukio Yanagisawa

598

Age
Ma

.-.....
rI:l

Low-latitude .-diatom zones NTD(1)

N. reinholdii

11

16B

1fJ6A1

10~'-

R. praebergonii ~

too:)

15A

= N.jouseae

too:)

~

(1)

.--

14

0

(1)

Thalassiosira
convexa

13e

ruB

IIJ3A1= N. miocenica I'Mt
(1)

.-:E
u
0

(1)

~

N.porteri~llA

C. yabeilOB
lOA

Actinocyclus
moronensis

9

1

..c

'-

~
~
~

~
~

~

10-

N. seminae
R. curvirostris
A. oculatus
N. koizumii

8

N. koizumii N. kamtschatica

7B

Neodenticula
kamtschatica

7A

R. californica

6B
6A
5D

T. schraderi
D. katayamae
D. dimorpha

5C

Thalassiosira yabei

5B

Denticulopsis
praedimorpha

5A

C. nicobarica

4B

D. hyaUna

4A

D.laula3B
3A

D. praelauta
C. kanavae

2

Thalassiosira /raga

1

Thalassiosira soinosa

~

S

I

~

....l
I---

North Pacificdiatom zones

9

'-

..s::
~
~

~

~

~

t--

I

~

u

5-

NPD
h12

17

P. doliolus

(1)

~

-

Koizumia(1)

C. coscinodiscus
=
0
(1)

.-:E
.-:Eu

(1)

'0
'0

15-

8

C. gigasvar. diorama

7

C. lewisianus

6

Cestodiscus
peplum~r--

5A= D. nicobarica -48
u
(1)

~

20

4A

T. pileus

-a c.
~

~

elegans

~

~~

~

58

(1)

0

'-

3

I
I
I
I

2

Figure 7. Stratigraphic distribution of Koizumia species. Low-latitude diatom zones after Barron(1985) and Fenner (1985), and North Pacific diatom zones after Akiba (1986). Correlation to the timescale of Berggren et al. (1985) is adjusted through Barron et at. (1985) and Oda (1986).

977.

Diatom genus Koizumia

ture (Figures II, 13, and 16). All species
have been reported from near-shore or onshore sequences mainly in the middle latitudes and rarely in low and high latitudes,
and have never been recorded in purely oceanic regions such as the central equatorial
Pacific.
Systematic descriptions
In this paper, the classification system ofRound et al. (1990) is adopted for thedescription of the genus Koizumia because
the system appear to be the most natural
diatom system at present.
Class Coscinodiscophyceae Roundet Crawford, 1990
Subclass Cymatosirophycidae Roundet Crawford, 1990
Order Cymatosirales Roundet Crawford, 1990
Family Cymatosiraceae Hasle,
von Stosch et Syvertsen, 1983
Subfamily Cymatosiroidae Hasle,
von Stosch et Syvertsen, 1983
Genus Koizumia Yanagisawa gen. nov.

Generic type.-Koizumia tatsunokuchiensis(Koizumi) Yanagisawa comb. nov.
Description.-Cell heterovalvate, rectangular in girdle view, forming inseparable chain
colonies. Separation valve or end valve that
separates chain colonies. Cingula with several bands with fine puncta. Valve slightly
convex, linear-Ianceolate in outline. Apices
with small apical pore field, slightly or strongly rostrate. Marginal ridge of sibling valvescompletely fused so that a set of fused sibling
valves seems as if it were a frustule. Marginal ridge with two longitudinal rows ofpores occluded with cribrum-like siliceous
layers perforated with regularly arranged
minute pores. A suture line present between
two longitudinal rows of pores on marginal
ridge. Rimoportula one per cell; a frustule599

consisting of a process valve and a nonprocess valve. Rimoportula located at subcentral position near the margin, obliq ue toapical direction. Transapical costae extending from both margins, continuous or broken.
Areolae circular, arranged in transapical rows
between each two transapical costae, and also
in longitudinal rows.
Comparison.- The genus is morphologically similar and probably related to the genera
Rossiella and Bogorovia in a number of common features such as the linear-Ianceolate
valve outline, the presence of marginal ridges,
the presence of the completely fused sibling
valves, the apical pore field, the one-per-cellpattern of rimoportula and so on. However,
Koizumia differs significantly from the latter
two genera by the cribrum-like siliceous
layers across the pores of the marginal ridge,
the suture line on the marginal ridge, and thepresence of transapical and longitudinal rowsof areolae on the valve face, all of which arenever observed in Rossiella nor Bogorovia.
Of the three features, the cribrum-likesiliceous layers are the most distinct character
unique to the genus Koizumia.
The genus Koizumia has a close resemblance to some genera under the family
Cymatosiraceae such as Cymatosira Grunow
and Campylosira Grunow in Van Heurck inthat they commonly possess a generally
dipolar outline, chain colonies connected bymarginal ridge or linking spines, rimportulain the pattern of one per cell, the presence ofocellus or apical pore field at each apex.
The genus Koizumia is within the morphological criteria of Cymatosiraceae definedby Hasle et al. (1983), and therefore it shouldbe placed in the family Cymatosiraceae.
However, Koizumia, as well as the related
genera Rossiella and Bogorovia, differs fromthe other members of this family in that it hascompletely fused marginal ridges. As it
appears that the actual fusion between
siliceous components of different cells has notbeen known in diatoms except for one example in the Chaetoceracea (Round et al., 1990,

Yukio Yanagisawa

600

p. 25), the completely fused marginal ridge isa nearly unique character to the three genera.
Stratigraphic occurrence.- The genus Koizumia appeared in the late Early Miocene
and disappeared near the end of the Pliocene(Figure 7).
Habitat.- The members of Koizumia
appear to have flourished as planktons forming long colony chains.
Geographic distribution.- The three species
which constitute the genus Koizumia havebeen reported from near-shore or onshore
sequences mainly in the middle latitudes andrarely in the low and high latitudes, and havenever been recorded in purely oceanic regions
such as the central equatorial Pacific where
both Rossiella and Bogorovia are distributed
abundantly (Figures I 1,13 and 16). Thispattern of distribution implies that the Koizumia species appear to have flourished inshallow-shelf marine environments. As they
are abundant especially off the western part ofcontinents such as Peru, Baja California andAngola, characterized by strong structural
upwelling and resultant high productivity,
the three species may be called upwelling
species. From this point of view, the three
species seem to constitute a distinct groupdifferent from the Rossiella and Bogorovia
species, all of which are distributed mainly inpurely oceanic tropical regions.
Etymology.-As the generic names of Rossiella and Bogorovia were both derived fromperson names, the name of this new genus
Koizumia is also taken from the name of aperson, Professor Itaru Koizumi of Hokkaido
University (Japan), who described the type
Table 3.

species of this genus as Rhaphoneis tatsunokuchiensis from the Pliocene deposits inJapan.
Discussion.- The genus is characterized bycribrum-like siliceous layers across the poresof marginal ridge and the presence of transapical and longitudinal rows of areolae on
the valve face. The three features are uniqueto the genus and have never been observed in
its related genera Rossiella and Bogorovia.
Koizumia is typically neritic in distribution
mainly in near-shore or upwelling regions of
the middle latitudes, and significantly
different from Rossiella and Bogorovia, bothof which have essentially an oceanic andtropical to subtropical distribution. Boththe morphological uniqueness and thediffering geographic distribution pattern are
considered to be distinctive enough to form
the basis of the erection of the new genus
Koizumia.
Key to species.-Key to species of thegenus based on light microscopy is presented
in Table 3.

Koizumia adaroi (Azpeitia)
Yanagisawa comb. nov.
Figures 8-1-7, 12,13; 9-1-3.

Basionym.-Cymatosira adaroi Azpeitia, 191 I, p.
20 I, pI. 9, fig. 5; Pastor, 199 I, fourth figure in p.
81.

Synonyms.- Rhaphoneis modiopunctata Haj6s, 1968,
p. 143, pI. 41, figs. 16-27; Haj6s, 1977, pI. 9, fig.
3; Rhaphoneis mediopunctata var. matraensis
Haj6s, 1968, p. 144, pI. 42, figs. 1-5; Cussia
mediopunctata (Haj6s) Schrader, I 974a, p. 542 ;Cussia mediopunctata var. matraensis (Haj6s)

Key to species of the genus Koizumia based on light microscopy.

1a. Transapical costae broken and longitudinal costae absent... ......................................... 2
1b. Transapical costae continuous and longitudinal costae present..................... K. akibae
2a. Valve with slightly rostrate apices ................................................................. K. adaroi
2b. Valve with strongly rostrate apices .............................................. K. tatsunokuchiensis

977.

Diatom genus Koizumia

Schrader, 1974a, p. 542; Cussia moholensis
Schrader, 1974a, p.542-543, fig. 1.1-4; Coscinodiscus praepaleaceus Schrader, Barron, 1975,
p. 136, pI. 7, fig. II ; Bogorovia moholensis(Schrader) louse, 1976, p. 1233; Cussia praepaleacea (Schrader) Schrader, Abbott and Andrews, 1979, p. 241, pI. 3, fig. 15; Cussia all
paleacea (Grunow) Schrader, Andrews, 1980, p.
28, pI. 2, fig. 2, pI. 4, fig. 6; Cussia praepaleacea
Schrader, Abbott, 1980, p.62, pI. 3, fig. 2; Abbott and Ernissee, 1983, p.299, pI. 12, fig. 3 ;Bogorovia tatsunokuchiensis (Koizumi) louse,
Barron, 1981 a, pI. 4, fig. 17; Rossiella mediopunctata (Haj6s) Gersonde et Schrader., 1984, p.
106; Yanagisawa, 1990b, pI. 1, fig. 6; Rossiellamediopunctata var. matraensis (Haj6s) Gersondeet Schrader, 1984, p. 106; Rossiella moholensis(Schrader) Gersonde et Schrader, 1984, p. 106;
Rossiella praepaleacea (Schrader) Gersonde etSchrader, 1984, p. 104-105, pI. I, figs. 11, 12 ;Powers, 1988, pI. 9, figs. 10-12; Rossiella moholensis (Schrader) Desikachary, Desikachary et
al, 1984, p. 338; Rossiella paleacea (Grunow)
Desikachary et Maheshwari, Haj6s, 1986, pI. 50,
figs. 18-20; Rossiella praepaleacea (Schrader)
Gersonde (sensu Abbott and Andrews, (979),
Fourtanier and Machare, 1988, pI. 3, fig. 39.

Original description.- Valva lanceolada de
29 p de longitud y 7 de anchura, con perl as
relativamente gruesas, no bien definidas ydispuestas en filas transversales. Cada una
de las filas centrales contiene cinco perl as, yeste numero disminuye hacia los dos extremos
hasta llegar a las punctas, en las que hay una
sola, que parece mas saliente que las otras.
En el ejemplar fotografiado se cuentan 20 6
22 filas en toda la longitud de la valva(Azpeitia, 1911, p. 201, as Cymatosira adaroi
Azpeitia).
Translation.-Valve lanceolate, 29pm inlength, 7 pm in width, with pearls (puncta)
relatively large, not well defined and disposedin transverse rows. Each one of the central
rows contains five pearls (puncta), and thisnumber decreases toward both ends until
reacing the points, where there is only one(puncta), which appears more salient than theothers. In the specimen photographed, 20 or
22 rows are counted in the whole length of thevalve.
Observation.- Valve linear-Ianceolate with601

slightly rostrate apices, 20-55 pm long, 6-8.5
pm wide (Figure 10). Valve face convex,
with transapical costae 8-9 in 10 pm, often
branching and interrupted to broken lines.
Areolae medium to fine, arranged in transapical rows between each two transapicalcostae and also in three to seven longitudinalrows. Marginal ridge of fused type with twolongitudinal rows of pores occuluded bycribrum-like layers (type 4). A sub central
rimoportula, one per cell, located near thevalve edge as the simple rimoportula with its
lip-shaped internal inner aperture opening
diagonally to the apical axis and its externalpore being flush with the marginal ridge
surface.
A long colony chain composed of seven
frustules has been observed with all sibling
valves connected to each other by the fused
marginal ridge (Fourtanier, 1987, pI. 16, fig.
5).
The species shows gradual variation in
valve shape. The specimens from the early
Middle Miocene Denticulopsis lauta Zone
(Figure 8-1) have a broadly lanceolate form,
whereas those from the upper Denticulopsis
hyalina Zone (Figures 8-3, 8-4) are more
slender. The valves from the late Middle
Miocene Denticuloptis praedimorpha Zone
(Figures 8-5, 8-7) are larger, showing moresimilarity to R. akibae. Among them, specimens from the D. hyalina Zone are the mostsimilar to the holotype specimen discoveredin Spain.
Holotype.-Azpeitia, 1911, pI. 9, fig. 5 or
Pastor, 1991, 4th figure in p.81 (Azpeitia871016-19, deposited in Instituto Tecnnol6gico GeoMinero de Dspana).
Type locality.-Sample from gypsiferous
deposits of the "serrata" (small ridge ofmountains), Lorca, Spain.
Type level.-Late Miocene in age, Messinian (Sancetta et al., 1985).
Comparison.-Koizumia adaroi very closely resembles K. akibae, but is distinguishedfrom the latter by its broken lines of transapical costae and the lack of longitudinal

Yukio Yanagisawa

602

costa (Figure 5). The species resembles K.
tatsunokuchiensis, but differs by non-rostrate
apices. This species has been often
misidentified as B ogoro via praepaleacea(Schrader) Jouse (e.g. Barron, 1975; Abbott
and Andrews, 1979; Gersonde and Schrader,
1984; Powers, 1988), but is clearly distinguished from the latter by the presence ofareolae on the valve face.
Stratigraphic range.-In DSDP Hole
438A, this species occurs from the upper partof the Denticulopsis hyalina Zone (NPD 4B)
to the middle part of the Denticulopsis
katayamae Zone (NPD 6A) (Figure 6).
However, its first occurrence may range down
to the late Early Miocene (Figure 7); thespecies is found from the early Middle
Miocene Oidawara Formation in Mizunami
area in central Japan, which can be correlatedwith the lower part of the Denticulopsis lauta
Zone (NPD 4A) (Figure 8-1). Moreover,the species occurs in the upper part of the late
Early Miocene Thalassiosira fraga Zone
(NPD 2) in the Nabuto Formation, Chiba,
Boso Peninsula, Japan (Figure 8- 13).
F ourtanier (1987) reported the stratigraphic range of Rossiella mediopunctata(Haj6s) Gersonde et Schrader in the South
Atlantic off Angola and Namibia. Although Rossiella mediopunctata is a synonymof Koizumia adaroi as will be discussed later,
Fourtanier's (1987) species concept of R.
mediopunctata is apparently broader thanthat of K. adaroi in this paper, including~

both K. adaroi and K. akibae. Therefore R.
mediopunctata in Fourtanier (1987) has alonger stratigraphic range than K. adaroi inthis paper. The last occurrence of R.
mediopunctata falls below the top of the
Nitzschia miocenica Zone (NTD 12) in theSouth Atlantic off Angola and Namibia(Fourtanier, 1987), which is apparently
younger than that in the North Pacific (Figure 7). The last occurrence of R. mediopunctata in Fourtanier (1987) is coincident withthat of K. akibae in the North Pacific (Figure
7).

Geographic distribution.- This species has
been mainly found in the middle-latitude
areas (Figure II). In the Northern Hemisphere, the species has been reported from
Spain (Azpeitia, 1911; Gersonde andSchrader, 1984; Monjanel, 1987), Hungary(Haj6s, 1968,1977,1986), the Atlantic coastof U.S.A. (Abbott and Andrews, 1979; Abbott, 1980; Andrews, 1980; Abbott and Ernissee, 1983; Powers, 1988), California andits environs (Barron, 1975, 1981a; Schrader,
1974a; Fourtanier, 1987) and Japan (Fourtanier, 1987; Yanagisawa, 1990b; thisstudy). In the Southern Hemisphere, thespecies occurs in the South Atlantic near
Angola (Fourtanier, 1987) and Peru (Fourtanier, 1987; Fourtanier and Machare, 1988).
It has never been identified in the low latitudes, e.g. the DSDP Hole 77B drilled in thetropical eastern Pacific. As this species has
been reported mainly from on-land or near-

Figure 8. LM photomicrographs of Koizumia species. Scale bar equals 10 ,urn. Arrow heads
indicate the location of rimoportula. 1-7. Koizumia adaroi (Azpeitia) Yanagisawa comb. nov. (I) Sample
Mzn 09, Oidawara Formation, Mizunami area, Gifu Prefecture, Japan (the Denticulopsis lauta Zone). (2,3)
Sample Nmy 13A, Nishimyo Formation, Niigata area, Japan (the Denticulopsis hyalina Zone). (4) DSDP
Hole 438A, 67-1, 27-32 cm. (5-7) Sample M32, Isozaki Formation, Ajigaura area, Japan (the Denticulopsis
praedimorpha Zone). 8-11. Koizumia akibae Yanagisawa sp. nov. (8) DSDP Hole 438A, 52-3, 36-38 cm.
(9) Holotype, DSDP Hole 438A, 50-6, 20-24 cm. (10) DSDP Hole 438A, 50-7, 10-11 cm. (II) DSDP Hole
438A, 52-4, 36-38 cm. 12, 13. Koizumia adaroi (Azpeitia) Yanagisawa comb. nov. (12) DSDP Hole 438A,
59-4, 17-21 cm. (13) Km 09, Nabuto Formation, Kamogawa, Chiba Prefecture, 80so Peninsula, Japan (theupper part of the Thalassiosira Jraga Zone). 14-25. Koizumia tatsunokuchiensis (Koizumi) Yanagisawacomb. nov. (14, 15) A-I, I 1.00-1 1.23 m, Tomioka, Fukushima, Japan. (16-18,20,22,24,25) JDS 8842, San
Felipe, Mexico. (19) Sample Ha 67 (Se 40), Tatsunokuchi Formation, Iwanuma, Miyagi, Japan. (21) D-I,
Sunda Forearc, off Java Island. (23) DSDP Hole 438A, 51-I, 16-20 cm.

977.

Diatom genus KoiZlonia

603

4

8

12

I

25

604

Yukio Yanagisawa

shore sequences, it seems to have flourished inshallow-shelf marine environments and may
be adapted to the coastal upwelling zones.
Dlscussion.- The species was originallydescribed as Cymatosira adaroi from theUpper Miocene gypsiferous deposits of Lorca,
Spain (Azpeitia, 1911). However, no one
referred to it before Pastor (1991) recently
presented an excellent photomicrograph ofthe type specimen. Gersonde and Schrader(1984) reported this species as Rossiella praepaleacea (Schrader) Gersonde et Schraderfrom the Lorca Basin. Gersonde andSchrader's (1984) specimens might have beenobtained from the same stratigraphic unit ofAzpeitia (1911) although the exact location is
not clear.
Rhaphoneis mediopunctata Haj6s, a
species described from the Miocene depositsin Hungary (Haj6s, 1968), is considered to bea synonym of K. adaroi because of the samemorphologic features. Haj6s (1968) also
described R. mediopunctata var. matraensis,
a variety that is distinguished from thenominated variety mediopunctata by the
number of middle longitudinal rows ofareolae; the variety mediopunctata has tworows while the variety matraensis has only
one row. However, this difference is thought
to be a continuous intraspecific variation, as
more clearly seen in K. tatsunokuchiensis (seeFigures 8-20, 8-14, 8-17), and therefore thevariety matraensis is also a synonym of K.
adaroi.
Cussia moholensis Schrader, which was
described by Schrader (1974a) from the experimental Mohole site off California, has morphologic characteristics well fitting those of
K. adaroi except for a very long valve. The
holotype and paratype specimens of C. moholensis may be identified as extremely longspecimens of K. adaroi, because they almost
fall within the variation of K. adaroi inbiometric plots (Figure 10). Cussia moholensis is therefore considered to be a synonym of K. adaroi. The specimens of C.
moholensis are similar to K. akibae, but areclearly distinguished from the latter by thebroken transapical costae. Fourtanier(1987) has already pointed out that C. moholensis is probably a synonym of Rossiellamediopunctata which is synomymized with
K. adaroi in this paper.
As pointed out by Fourtanier (1987, p.
107 -108), there is some doubt that theholotype specimen of Cussia praepaleacea
Schrader chosen by Schrader (1973) may be
Koizumia adaroi. Despite the original statement that C. praepaleacea has a hyaline valve
face (absence of areolae), the photographed
holotype seems to have circular areolae
between the transapical costae on the valve
face. However, I cannot assert the presenceof areolae with confidence because of therather poor picture of the holotype.

Koizumia akihae Yanagisawa sp. nov.
Figures 8-8-11; 12-1-7.

Synonyms.-Rossiella praepaleacea (Schrader) Gersonde, Akiba et al., 1982, pI. 3, fig. 93. Rossiella praepaleacea (Schrader) Gersonde et Schrader,
Akiba, 1986, p.445, pI. 19, fig. 6.

Description.-Valve linear-lanceolate, 2850 Jim long, 7-10 Jim wide. Apices not rostrate. Transapical costae, 7-8 in 10 Jim, rarely branching and almost continuous, notbroken. A faint longitudinal costa present
one areola apart from a margin. Marginal
ridge of fused type with two longitudinalrows of subrounded pores occluded bycribrum-like layers (type 4). A subcentral
rimoportula, one per cell, located near thevalve edge as the simple rimoportula with its
lip-shaped internal inner aperture opening
diagonally to the apical axis and its externalpore being flush with the marginal ridge
surface. Cingulum consisting of two or threebands punctated with a row of small puncta.
Holotype.-Figure 8-9 (GSJF14590 deposited in the Geological Survey of Japan).
Type sample.-DSDP Hole 438A, Core 50,
Section 6, Interval 20-24 cm, 40 37.79'N, 143°
14.l5'E, northwest Pacific, off Honshu, Japan.
0

977.

Diatom genus Koizumia

605

Figure 9. SEM photomicrographs of Koizumia adaroi (Azpeitia) Yanagisawa comb . nov. Sample
M32, Isozaki Formation , Ajigaura area, Japan. Broad and narrow scale bars equal 5,um and l,um,
respectIve ly. Arrows IndIcate rImoportu lae. 1. Inner view of va lve. 2. Ob lique view. 3. Enlarged
vIew of a destroyed valve.

100

10

10

B

A

•

80

•

2-5

~

""c

~ 40

0

0

0

0

o

*
+

+ 0

9

E

::t

CDO

:::
""

-§

+
+

E 60

C

9
E

::t

0

" '"' ' 0

-g""

7

00

E

0
0

Z

6

0

• •

+

++

:I

20

0

., '"

0

~

0

]

0

'-'

~

0

0

:::

0

]

7

0

E

++

+

'"

0

•

+ ....

:IZ
OK. adaroi

6

+t

+t

e K. akibae+ Haj6s (1968)• "c. moholensis"
0
5

9

6
Width (~m)

5
10

II

0

20

40
60
Length (~m)

80

100

5
5

6

7
8
9
Width (v.m)

10IIFigure 10. Size variation In Koizumia adaroi (Azpeitia) Yanagisawa comb . nov. and K. akibae
Ya nagisawa sp. nov. A. Scatter plot of val ve width versus length. B. Scatter plot of val ve length versu s
the number of transapical costae in 10,um. C. Scatter plot of va lve width versus the number of transapica l costae in 10,um . Samp les from no. 1, 5, 8 in Table I. Pluses indicate the size of Rhaphoneis
mediopunctata Hajos and R. mediopunctata var. malraensis Hajos (Hajos, 1968). Closed squares indicate the size of Cussia moholensis Schrader (Schrader, 1974a).

Type level. - Late Miocene in age, Thalassionema schraderi Zone (N PO 6B) .
Comparison. - Koizumia abibae resemb les
K. adaroi , but is distinct from the latter inhaving nearly continuous transapical costae,a longitudina l costa (Figure 5), slight ly
broader valve width and slightly broader
spacing of transapical costae (Figure 10).
The species is similar to K. tatsunokuchiensis,b ut differs from the latter mainly by non -rostrate apices and nearly continuous tran sapical costa. The species has been reported
as Rossiella praepaleacea by Akiba et al.
(1982) and Akiba (1986), but K. akibae has
areo lae on the valve face whereas B. praepaleacea complete ly lacks areolae.
Stratigraphic range .-In the North Pacific,
the spec ies occurs from the upper part of the
Denticulopsis katayamae Zone (NPD 6A) tothe midd le part of the Rouxia californica

606

Yukio Yanagisawa

Figure 11. Geographic distribution of Koizumia adaroi (Azpeitia) Yanagisawa comb. nov. Closed
circles: localities reported with figures. Open circle: locality reported without figures. 1. Lorca, Spain(Azpeitia, 1911; Pastor, 1991; Gersonde and Schrader, 1984). 2. Puente Gentil, Guadalquivir Basin,
Spain (Monjanel, 1987). 3. Aguilar, Guadalquivir Basin, Spain (Monjanel, 1987). 4. San Felix,
Guadalquivir Basin, Spain (Monjanel, 1987). 5. Szurdokpiispoki, Hungary (Haj6s, 1968). 6. Szokolya,
Hungary (Haj6s, 1977, 1986). 7. DSDP Hole 369A, eastern north Atlantic margin off northwest Africa(Schrader, 1977). 8. Cores ANG I and ANG 2, South Atlantic off Angola (Fourtanier, 1987). 9.
DSDP Hole 363, South Atlantic off Namibia (Fourtanier, 1987). 10. Petersburg, Virginia, U.S.A.
(Andrews, 1980). 11. Pungo River Formation, RA-13-GRL, Beaufort County, North Carolina, U.S.A.
(Abbott and Ernissee, 1983). 12. Hawthorn Formation, Dawsons Landing, South Carolina, U.S.A.
(Abbott and Andrews, 1979). 13. Pungo River Formation, Onslow Bay continental shelf cores OB 108
and OB 95, off North Carolina (Powers, 1988). 14. Drill core AMCOR 6002, off Georgia, U.S.A.
(Abbott, 1980). 15. Pisco Formation, Pisco, Peru (Fourtanier and Machare 1988; Fourtanier, 1987).
16. DSDP Hole 470, northeast Pacific off Baja California (Barron, 1981a; Fourtanier, 1987). 17.
Experimental Mohole Drilling Guadalupe Site, northeast Pacific off Baja California (Schrader, 1974a).
18. Monterey Formation, Lompoc, California, U.S.A. (Barron, 1975). 19. DSDP Hole 438A, northwest
Pacific off Japan (this study; Fourtanier, 1987). 20. M32, Isozaki Formation, Ajigaura, Ibaraki, Japan(this study). 21. Nishimyo Formation, Sumon, Niigata, Japan (this study). 22. Otokawa Formation,Endo, Toyama, Japan (Yanagisawa, 1990b). 23. Oidawara Formation, Mizunami, Gifu, Japan (thisstudy). 24. Nabuto Formation, Kamogawa, Chiba, Japan (this study).

Zone (NPD 7A) (Figures 6, 7).
Geographic distribution.- At present, thisspecies is found only in DSDP Hole 438A
(Akiba, 1986, this study) and from theOmatsuzawa Formation in Matsushima area,
Japan (Akiba et al., 1982) (Figure 13). It is
probably a middle-latitude species following
the distribution pattern of the related species
K. adaroi and K. tatsunokuchiensis.
Etymology.- This new species is named inhonor of Mr. Fumio Akiba, who first figured

this species (Akiba et al., 1982; Akiba,1986).

Koizumia tatsunokuchiensis (Koizumi)
Yanagisawa comb. nov.
Figures 8-14-25, 14-1-9.

Basionym.-Rhaphoneis tatsunokuchiensis Koizumi,
1972, p.394, pI. 42, figs. 3,4

Synonyms.-Rhaphoneis

tatsunokuchiensis Koizumi; Koizumi, 1973, pI. 20, figs. 14, 15; 1975a,

977.

Dia tom genus Koizumia

Figure 12. SEM ph oto microg ra phs o f Koizumia akibae Ya nag isawa sp. nov. DSDP Ho le 438 A, 53 2, 30- 31 cm . Broad and na rrow sca le bars equ a l 5 J.lm a nd I J.lm , res pecti ve ly. 1,2. Inn er views of ava lve. Arrows ind ica te rim o po rtul ae. 3. Enl a rged view of ma rgin a l rid ge, show in g a rim o po rtul a(a rrow) a nd cribrum-Iik e sil iceo us layers across th e po res of margin a l ridge. Note a suture line between
two siblin g va lves. 4. Enl a rged view o f a n a pex. 5. T wo sets of fused siblin g va lves. 6. Ma rgin a l rid gewith cin gulum ba nd s. 7. E nl a rged view o f Fig. 12- 5, show in g th e extern al o penin g of a rimo po rtul a(a rro w) .

607

Yukio Yanagisawa

608

.. '

Figure 13. Geographic distribution of Koizumia akibae Yanagisawa sp. nov. Closed circles: localities reported with figures. 1. DSDP Hole 438A, northwest Pacific off Japan (this study; Akiba, 1986).
2. Omatsuzawa Formation, Matsushima, Miyagi, Japan (Akiba et a!., 1982).

p. 804; Cussia tatsunokuchiensis (Koizumi)
Schrader, 1974a, p. 543, figs. 1-6, 1-7; Schrader,
1974b, p. 914; Koizumi, 1975b, p. 876, pI. 4, figs.
33-35; 1975c, p. 619, pI. I, fig. 23; Koizumi and
Ujiie, 1976, pI. 12, fig. 7; Harper, 1977, pI. 3, fig.
7; Schrader and Gersonde, 1978, p. 151, pI. 2, fig.
5; Barron, 1980, p. 672, pI. I, fig. 31, pI. 4, fig. 3 ;Kulm et a!., 1981, pI. I, fig. 12; Akutsu, 1982,
pI. 20, fig. 2099; Bogorovia tatsunokuchiensis(Koizumi) Jouse, 1976, p. 1233; Koizumi andTanimura, 1985, pI. 1, fig. 19; Boden, 1992, p.
135, pI. 2, figs. 2, 3; Bogorovia mediopunctata(Hajos) Jouse, 1976, p. 1233, fig. 4; Jouse ed.,1977, pI. 45, fig. 31 ; Rossiella tatsunokuchiensis(Koizumi) Gersonde, Akiba et al., 1982, pI. III,
figs. 90, 91 ; Desikachary et al., 1984, p. 338 pI.
I, fig. 7; Barron, 1985, p. 790, fig. 9.8; Hirayama
and Uemura, 1985, pI. I, fig. 7; Ito, 1986, pI. 3,
fig. II; Taketani et al., 1986, pI. 3, figs. 10, II ;Fourtanier and Machare, 1988 pI. 3, fig. 40;
Rossiella tatsunokuchiensis (Koizumi) Gersondeet Schrader, 1984, p. 106; Koizumi, 1986, pI. I
fig. 5; Akiba, 1986, p.445, pI. 19, figs. 7-9 ;Akiba, 1987, pI. 2, fig. 15; Yanagisawa, 1987, pI.
5, figs. 1,2; Taketani et a!., 1990, pI. 10, figs. 15,
16; Watanabe, 1990, pI. I, fig. 10; Yanagisawa
et al., 1991, pI. 24, fig. 4; "Cussia" mediopunctata (Hajos) Schrader, Akiba et al., 1982, pI. 3,
fig. 92; Rossiella cf. tatsunokuchiensis (Koizumi) Gersonde et Schrader, Akiba, 1986, p. 445,
pI. 19, figs. 10-12; Rossiella praepaleacea
Schrader et Gersonde, Schrader and Castaneda,
1990, pI. I, figs. 1-3.

Original description. - Val ve I anceo I aterhombic or lanceolate, with produced apices.
The length of apical aXIs 20-36 jim,~Figure 14. SEM photomicrographs of Koizumia tatsunokuchiensis (Koizumi) Yanagisawa comb.
nov. (1-4,6,7) Sample Ya 185, Tatsunokuchi Formation, Matsushima area, Japan. (5,8,9) DSDP Hole
438A, 50-6,20-24 cm. Broad and narrow scale bars equal 5 JLm and I JLm, respectively. 1,2. Inner viewsof a process valve. Arrow indicates a rimoportula. 3. Short colony chain composed of three sets of fused
sibling valves. 4. Marginal ridge with cingulum bands. 5. Enlarged view of an apex. 6. Enlarged viewof marginal ridge. Arrow head and arrow indicate a rimoportula and its outer opening, respectively. 7.
Inner view of a non-process valve. 8. Enlarged view of marginal ridge, showing cribrum-like siliceous
layers covering the pores of marginal ridge. 9. Obique view of a set of fused sibling valves. Note a sutureline between the two valves.

977.

Diatom genus Koizumia

609

Yukio Yanagisawa

610

9

9

70

B

A

C

Koizumia rarsunokuchiensis

60·· ...
•I •
.:
... .

50

~

ic 40
~

e

::I.

.... - . .

~

~

~

!!

~ 7

'0

.8e

• • • : I

~

.. ..

u

: I •

30

8

- . .... _. .-. . • §.

u

•

7

. ..

'0

.8e
"

Z6

Z 6

20
5

5

\0

4

5

7
6
Width(J1II1)

9

\0

10

20

50
40
30
Length (J1II1)

60

70

4

5

8
6
7
Width(J1II1)

9

10

Figure 15. Size variation in Koizumia tatsunokuchiensis (Koizumi) Yanagisawa comb. nov. A.
Scatter plot of valve width versus length. B. Scatter plot of valve length versus the number of transapicalcostae in 10 pm. C. Scatter plot of valve width versus the number of transapical costae in 10 pm.
Samples from no. 1-4,9 in Table 1.

tranapical axis 5-10 ,urn. Valve surface flat,
covered with large sub-rectangular puncta, 68 in 10 ,urn. Puncta in weakly radiating
curved lines on both sides of a narrowed
linear pseudoraphe, and are interrupted by
the sub-marginal hyaline line extending parallel to the valve margin. The number of longitudinal parallel rows of puncta is about 6(as Rhaphoneis tatsunokuchiensis Koizumi,
1972, p. 349).
Observation.- Valve linear-lanceolate or
rhombic with strongly rostate apices, 20-64,urn long and 5-9,um wide (Figure 15).
Valve face convex, punctated with round
areolae arranged to form three to six longitudinal rows in 10 ,urn. Marginal ridge of
fused type with two longitudinal rows ofsubrounded pores occuluded by cribrum-likelayers (type 4), though the layers have been
dissolved in many cases. A subcentral
rimoportula, one per cell, located near thevalve edge as the simple rimoportula with its
lip-shaped internal inner aperture opening
diagonally to the apical axis and its externalpore flush with the marginal ridge surface.
Cingulum consisting of several bands, each ofwhich is perforated by a row of small puncta.
Holotype.-Koizumi, 1972, pI. 42, fig. 4,

Slide no. 6717, position England Finder T444, deposited in Dr. Koizumi's personal
diatom collections.
Type sample.-Sample Tomioka 36,
Tomioka Town, Futaba district, Fukushima
Prefecture, northeast Honshu, Japan.
Type leve/.-Late Pliocene in age, theNeodenticula koizumii-Neodenticula kamtschatica Zone (NPD 8). The type sample ofthis species was originally assigned to the
Tatsunokuchi Formation in the lower Sendai
Group (Koizumi, 1972), but it is now included in the Dainenji Formation in the upper
Sendai Group (Yanagisawa, 1990a).
Comparison.- This species closely resembles K. adaroi, but differs by the strongly
rostrate apices (Figure 5). Koizumia tatsunokuchiensis is distinguished from K. akibaeby having strongly rostrate apices, discontinuous transapical costae, the lack of a longitudinal costa and slightly smaller valve size.
Stratigraphic range.- This species firstoccurs in the upper part of the early Late
Miocene Denticulopsis katayamae Zone
(NPD 6A) in DSDP Hole 438A (Table 2,
Figure 6). However, the first occurrence of
this species has been placed in the middle partof the Neodenticula kamtschatica Zone

977.

Diatom genus Koizumia

Pacific Ocean

Figure 16. Geographic distribution of Koizumia tatsunokuchiensis (Koizumi) Yanagisawa comb.
nov. Closed circles: localities reported with figures. Open circles: localities reported without figures.
1. DSDP Hole 438A, northwest Pacific off Japan (this study; Barron, 1980; Akiba, 1986; Fourtanier,1987). 2. DSDP Hole 584, northwest Pacific off Japan (Akiba, 1986). 3. Tatsunokuchi Formation,
Matsushima, Miyagi, Japan (Akiba et al., 1982; this study). 4. Omatsuzawa Formation, Matsushima,
Miyagi, Japan (Akiba et al., 1982). 5. Tatsunokuchi Formation, Sendai, Miyagi, Japan (Koizumi, 1973;
Yanagisawa, 1990a). 6. Tatsunokuchi Formation, Iwanuma, Miyagi, Japan (Akutsu, 1982; Yanagisawa, 1990a; this study). 7. Dainenji Formation (Tomioka F.), Tomioka, Fukushima, Japan (Koizumi,
1972; Taketani et al., 1986; Yanagisawa et al., 1989; Yanagisawa, 1990a; this study). 8. Taga
Group, Hirono, Fukushima, Japan (Koizumi, 1975c). 9. Yotsukura Formation, Iwaki, Fukushima,
Japan (Taketani et al., 1990). 10. Ikego and Zushi Formations, Ikego, Zushi, Kanagawa, Japan (Maruyama, 1993a, b). 11. Nobori Formation, Kochi, Shikoku, Japan (Koizumi and Ujiie, 1976). 12.
Enbetsu Formation, Shosanbetsu, Hokkaido, Japan (Harper, 1977). 13. Akaishi and Maido Formations,
Ajigasawa, Aomori, Japan (Hirayama and Uemura, 1985; Akiba and Hiramatsu 1988). 14. Nakayama
Formation, Sado Island, Niigata, Japan (Akiba, 1987). 15. Ao Formation, Himi, Toyama, Japan(Watanabe, 1990). 16. Takakubo Mudstone, Tsuribe, Ishikawa, Japan (Ito, 1986). 17. DSDP Hole
797B, Japan Sea (Koizumi, 1992). 18. DSDP Hole 794A, Japan Sea (Koizumi, 1992). 19. DSDP Hole
796A, Japan Sea (Koizumi, 1992). 20. DSDP Hole 795A, Japan Sea (Koizumi, 1992). 21. DSDP Hole
299, Japan Sea (Koizumi, 1975a). 22. DSDP Hole 301, Japan Sea (Koizumi, 1975a) 23. DSDP Hole
581, northwest Pacific (Koizumi and Tanimura, 1985). 24. DSDP Hole 580, northwest Pacific (Koizumi
and Tanimura, 1985). 25. DSDP Hole 579, northwest Pacific (Koizumi and Tanimura, 1985). 26.
DSDP Hole 578, northwest Pacific (Koizumi and Tanimura, 1985; Boden, 1992). 27. DSDP Hole 310,
northwest Pacific (Koizumi, 1975b). 28. Sisquoc Formation, Harris Grade, Santa Barbara, California, U.
S.A. (Barron and Baldauf, 1986). 29. Experimental Mohole Drilling Guadalupe site, northeast Pacific off
Baja California (Schrader, 1974a). 30. San Felipe, Baja California, Mexico (this study). 31. Dredge
sample 7,706 from sea floor off Peru (Kulm et al., 1981). 32. Delfin well off Peru (Schrader andCastaneda, 1990). 33. Pisco Formation, Pisco, Peru (Fourtanier and Machare, 1988). 34. Caleta
Herradura de Mejillones, Antofagasta, Chile (Koizumi, 1990). 35. DSDP Hole 362, South Atlantic off
Namibia (Fourtanier, 1987). 36. Cores ANG I and ANG 2, South Atlantic off Angola (Fourtanier,1987). 37. Lorca, Spain (Gersonde, 1980). 38. San Felix, Spain (Monjanel, 1987). 39. Dredge sample
D-I, equatorial Indian Ocean off Java, Indonesia (Yanagisawa, 1987; this study). 40. DSDP Hole 213,
equatorial Indian Ocean (Schrader, 1974b; Desikachary et al., 1984). 41. DSDP Hole 215, equatorial
Indian Ocean (Schrader, 1974b).

611

612

Yukio Yanagisawa(NPD 7B) near the Miocene/Pliocene boundary (Barron, 1980,1985; Akiba, 1986; Koizumi, 1985; Koizumi and Tanimura, 1985)
and estimated at 5.26 Ma (Barron, 1992).
This large discrepancy may be due to theextremely sporadic and sparse occurrence of
this species below the Miocene/Pliocene
boundary. Probably the occurrence of thisspecies in the Upper Miocene interval may
have been overlooked by earlier researchers
because of the scarcity of this species. The
increase in abundance of this species aroundthe Miocene/Pliocene boundary (Figure 7) is
coincident with the previously reported firstoccurrence of this species.
In DSDP Hole 472 (northeast Pacific, off
Baja Colifornia, Mexico), Barron (1981 a)reported the first occurrence of this species atthe base of the Thalassiosira antiqua Zone,
which can be estimated at 7.6 Ma (Barron,1992), and so slightly later than in Hole 438A.
In the South Atlantic, the first occurrenceof this species falls in the Coscinodiscus yabei
Zone (NTD 10) (Fourtanier, 1987), which isalmost synchronous to that in North Pacific
DSDP Hole 438A (Figure 7).
The last occurrence of this species in the
middle- to high-latitude North Pacific has
been reported in the upper part of the
Neodenticula koizumii-N. kamtschatica
Zone (NPD 8) (Barron, 1980, 1985) and estimated at 2.5-2.55 Ma by Barron (1992). In
the tropical Indian Ocean, the last occuurrence of R. tatsunokuchiensis lies near the top of
the Nitzschia jouseae Zone (NTD 14) according to Schrader (1976). However, K. tatsunokuchiensis was illustrated from the C Subzone of the Rhizosolenia praebergonii Zone
(NTD 15C, latest Pliocene in age) in dredge
samples obtained from the Sunda Forearc off
Java Island (Yanagisawa, 1987), suggestingthat its last occurrence may range up at least
to the latest Pliocene in this area (Figure 7).
In the South Atlantic, the species last occurs
in the uppermost Nitzschia jouseae Zone
(NTD 14) which coincides with that in thetropical Indian Ocean (Fourtanier, 1987).

Thus the first and last occurrences of thisspecies appear largely diachronous regionally. However, combination of all data
available indicates that the species first
appeared in the early Late Miocene anddisappeared near the end of the Pliocene(Figure 7).
Geographic distribution.- Koizumia tatsunokuchiensis has been reported from numerous areas of the world (Figure 16). The
species seems to be distributed mainly in the
middle latitudes, but it also occurs in low andhigh latitudes. The species has been recorded more commonly from on-land sequences
than from purely oceanic sediments. Moreover, this species occurs fairly commonly inintrabay sediments such as the Tatsunokuchi
Formation. These occurrences imply that
this species flourished in near-shore shallow
environments.
Etymology.- The species name is derived
from the Tatsunokuchi Formation fromwhich the species was firstly described.
However, the type material of this species is
not from the formation, but from the Dainenji Formation as discussed above.
Conclusion
A new fossil marine diatom genus Koizumia Yanagisawa is proposed for three fossil species. The morphology of the genus ischaracterized by crib rum-like siliceous layers
across the pores of the marginal ridge, thesuture line on the marginal ridge and thepresence of transapical and longitudinal rowsof areolae on the valve face. Such features
are unique to the genus and never present in
its related genera Rossiella and Bogorovia.
Koizumia is distributed mainly in near-shoreor upwelling regions of the middle latitudes,
and thus shows significantly different distribution pattern from Rossiella and Bogorovia,
both of which are essentially oceanic andtropical to subtropical genera. Such morphological uniqueness and differing geographic distribution pattern of the genus are977.

Diatom genus Koizumia

considered to be distinctive enough to establish a new genus. Some features of thisgenus such as the colony chain formation
connected by marginal ridges, a rimoportulain the pattern of "one per cell" and thepresence of apical pore field suggest that thegenus can be placed in the family Cymatosiraceae Hasle, von Stosch et Syvertsen.
Acknowledgments

I would like to express special thanks to
Fumio Akiba (JAPEX Research Center ofJapan Petroleum Exploration Co. Ltd.) and
Itaru Koizumi (Hokkaido University) who
encouraged me to study this genus, providing
thoughtful advice, and reviewed the manuscript carefully. I am very grateful to John
A. Barron (U.S. Geological Survey) andElisabeth Fourtanier (California Academy of
Sciences) for their critical but constructive
thorough review of the early draft of thismanuscript and their helpful suggestions ontaxonomy and stratigraphy. I also thankJohn A. Barron, Fumio Akiba, Yoshihiro
Tanimura, Yokichi Takayanagi, Toshiaki
Maruyama, Hiroshi Kobayashi who kindly
offered the chance to examine DSDP materials. I am greatful to Akira Nishimura,
Fumio Yoshida, Eiichi Honza for providing
samples used in this study and to Kimio
Okumura, Koichi Nakamura and Tamotsu
Nagumo for their kind advice and assistancein the literature search. I would like tothank Yuji Endo for translating the originaldescription of R. adaroi from Spanish into
English.
References cited
Abbott, W.H., 1980: Diatoms and stratigraphicallysignificant silicoflagellates from the Atlantic
Margin Coring Project and other Atlantic marginsites. Micropaleontology, vol. 26, p.49-80.
- - and Andrews, G.W., 1979: Middle Miocene
marine diatoms from the Hawthorn Formation
within the Ridgeland Trough, South Carolina
and Georgia. Micropaleontology, vol. 25, p.

613

225-271.
- - and Ernissee, J.J., 1983: Biostratigraphy andpaleoecology of a diatomaceous clay unit in the
Miocene Pungo River Formation of Beaufort
County, North Carolina. In, Ray, C.E. ed.,Geology and paleontology of the Lee Creek
Mine, North Carolina, I, Smithsonian Contributions to Paleobiology, vol. 53, p.287-353.
Akiba, F., 1986: Middle Miocene to Quaternary
diatom biostratigraphy in the Nankai Troughand Japan Trench, and modified Lower Miocene
through Quaternary diatom zones for middle-tohigh latitudes of the North Pacific. In, Kagami,
H., Karig, D.E., Coulbourn, W.T., et al, Init.
Rep. DSDP., vol. 87, p.393-481. U.S. Govt.
Printing Office, Washington, D.C.
- - , 1987: Neogene diatom biostratigraphy of the
Nakayama-Toge section, Sado Island, Japan andits relation to the Funakawa Floral Change
Plane of Yamanoi (1978). Pub. Sado Museum,no. 9, p.85-101. (in Japanese with English
abstract)- - and Hiramatsu, c., 1988: Neogene diatom biostratigraphy in Ajigasawa, Goshogawara andShimokita areas, Aomori Prefecture, Japan. In,
Iijima, A. ed., Study of Tertiary SiliceousRocks, p. 35-51. (in Japanese, title translated)- - and Yanagisawa, Y., 1986: Taxonomy, morphology and phylogeny of the Neogene diatom
zonal marker species in the middle-to-high latitudes of the North Pacific. In, Kagami, H.,
Karig, D.E., von Coulbourn, W.T., et al, In it.
Rep. DSDP., vol. 87, p.483-554. U.S. Govt.
Printing Office, Washington, D.C.
- - , - - and Ishii, T., 1982: Neogene diatom
biostratigraphy of the Matsushima area and its
environs, Miyagi Prefecture, Northeast Japan.
Bull. Geol Surv. Japan, vol. 33, p.215-239. (inJapanese with English abstract)
Akutsu, J., 1982: Neogene diatoms. In, Fujiyama,
I. et al. eds., Illustrations of the Japanese
Paleoorganisms for Student, p.418-423. Hokuryukan, Tokyo, Japan. (In Japanese, title
translated)
Andrews, G.W., 1980: Neogene diatoms from Petersburg, Virginia, Micropaleontology, vol. 26, p. 1748.
Anonymous, 1975: Proposal for a standardization of
diatom terminology and diagnoses. Beih. zur
Nova Hedwigia, no. 53, p. 323-354.
Azpeitia, M., 1911: La diatomologia espanola en loscomienzos del siglo XX. Asociaci6n Espanolapara el Progreso de las Ciencias, Congreso deZaragoza (Primer Congreso, 1908), vol. 4, p. 1320 (in Spanish) (through Sancetta, C.A. et al.
eds., Catalogue of Diatoms, Book 1, Micropaleontology Press, New York).

614

Yukio Yanagisawa

Barron, J.A., 1975: Late Miocene-Early Pliocene
marine diatoms from southern California.
Palaeontographica, Abt. B, vol. 151, p.97-170.
- - , 1980: Lower Miocene to Quaternary diatom
biostratigraphy of Leg 57, off northeastern Japan,
Deep Sea Drilling Project. In, Scientific Party,
Init. Rep. DSDP., vols.56 and 57, p.641-685.
U.S. Govt. Printing Office, Washington, D.C.
- - , 1981 a: Late Cenozoic diatom biostratigraphy
and paleoceanography of the middle-latitude
eastern North Pacific, Deep Sea Drilling Project
Leg 63. In, Yeats, R.S., Haq, B.U., et al., In it,
Rep. DSDP., vol. 63, p.507-538. U.S. Govt.
Printing Office, Washington, D.C.
- - , 1981 b: Middle Miocene diatom biostratigraphyof DSDP Site 77B in the eastern equatorial
Pacific. Geosci. Jour., vol. 2, p. 137-144.
- - , 1985: Miocene to Holocene planktic diatoms.
In, Bolli, H.M., Saunders, J.B. and Perch-Nielsen,
K., eds., Plankton Stratigraphy, p.763-809.
Cambridge Univ. Press, Cambridge.
- - , 1992: Neogene diatom datum levels in theequatorial and North Pacific. In, Ishizaki, K.
and Saito, T. eds., Centenary of Japanese
Micropaleontology, p.413-425. Terra Scientific
Publishing Co., Tokyo.
- - and Baldauf, J.G., 1986: Diatom stratigraphy ofthe lower Pliocene part of the Sisquoc Formation, Harris Grade Section, California. Micropaleontology, vol. 32, p.357-371.
- - , Keller, G. and Dunn, D.A., 1985: A multiple
microfossil biochronology for the Miocene.
Geol Soc. America, Mem. 163, p. 21-36.
Berggren, W.A., Kent, D.V., Flynn, J.J. and Van
Couvering J.A., 1985: Cenozoic geochronology.
Geol Soc. America Bull., vol. 96, p. 1407-1418.
Boden, P., 1992: Quantitative biostratigraphy of
Neogene diatoms from the Norwegian Sea, North
Atlantic and North Pacific. Stockholm Contribution in Geology, vol. 42, p. 123-202.
Desikachary, T.V. and Maheshwari, c.L., 1958:
Fossil diatoms from Colebrook Island. Jour.
Indian Bot. Soc., vol. 38, p. 7-41.
- - , Latha, Y. and Ranjitha, Devi, K.A., 1984:
Rossiella and Bogorovia: two fossil diatom genera. Palaeobotanist, vol. 32, p.337-340.
Fenner, J., 1984a: Middle Eocene to Oligocene
planktonic diatom stratigraphy from Deep Sea
Drilling sites in the South Atlantic, equatorial
Pacific, and Indian Ocean. In, Hay, W.W.,
Sibuet, J.-c., et al., [nit. Rep. DSDP., vol. 75, p.
1245-1270. U.S. Gov!. Printing Office,Washington, D.C.
- - , 1984b: Eocene-Oligocene planktic diatom
stratigraphy in the low latitudes and the highlatitudes. Micropaleontology, vol. 30, p.319342.

- - , 1985: Late Cretaceous to Oligocene planktic
diatoms. In, Bolli, H.M., Saunders, J.B. andPerch-Nielsen, K., eds., Plankton Stratigraphy,
p. 713-762. Cambridge U niv. Press, Cambridge.
Fourtanier, E., 1977: Diatomees Neogenes d' Afriqueapproache biostratigraphique en milieux marin(sud-ouest Africain) et continental. Doctoral
thesis of University of Paris 6, 365 p. (Memoires
des Sciences de la Terre, Universite Curie, Paris
no. 87-44).
- - and Machare, J., 1988: Late Eocene to Pliocene
marine diatoms from Peru. Proc. 9th International Diatom Symposium, p. 151-163. Biopress Ltd., Bristol and Koeltz Scientific Books,
Koenigstein.
Gersonde, R., 1980: Palaookologische und biostratigraphische Auswertung von Diatomeenassoziationen aus dem Messinium desCaltanissetta-Beckens (Sizilien) und elmger
Vergleichs-Profile in SO-spanien, NW-Algerien
und auf Kreta. Dissertation zur Erlangung desDoktorgrades der Mathematisch-N aturwissenschaftlichen Fakultat der Christian-AlbrechtsUniversitat zu Kiel, p. 1-393.
- - and Schrader, H., 1984: Marine planktic diatom
correlation of lower Messinian deposits in thewestern Mediterranean. Marine Micropaleont.,
vol. 9, p.93-110.
Haj6s, M., 1968: Die Diatomeen der Miozanen Ablagerungen des Matravorlandes. Geologica
Hungarica, Ser. Palaeont., vol. 37, p. 31-401.
- - , 1977: Miocene diatomaceous sediments at Szokolya Village and vicinity, north Hungary.
Foldtani Intezet Evi Jelen tese , 1975-rol, p. 39-82.
(in Hungarian with English abstract)- - , 1986: Stratigraphy of Hungary's Miocene
diatomaceous earth deposits. Geologica Hungarica, Ser. Palaeont., vol. 49, p. 1-339. (inHungarian and English)
Harper, H.E. Jr., 1977: Diatom biostratigraphy. In,
Ujiie, H., Saito, T., Kent, D., Thompson, P.R.,
Okada, H., Klein, G.V., Koizumi, I., Harper,
H.E. Jr. and Sato, T., Biostratigraphy,
paleomagnetism and sedimentology of late Cenozoic sediments in northeastern Hokkaido,
Japan. Bull Natn. Sci. Mus., Tokyo, Ser. C(Geol.), vol. 3, p.49-102.
Hasle, G.R., von Stosch, H.A. and Syvertsen, E.E.,
1983: Cymatosiraceae, a new diatom family.
Bacillaria, vol. 6, p. 9-156.
Hirayama, J. and Uemura, H., 1985: Geology of the
Ajigaura district, Geological Survey of Japan,
Quadrangle Series (Scale I : 50,000), p. 1-86.
Ito, Y., 1986: Diatom biostratigraphy of the Neogene
system in the Hokuriku Province, central Japan.
NOM (News of Osaka Micropaleontologists),
no. 14, p. 1-27.

977.

Diatom genus Koizumia

Jouse, A.P., 1973: Diatoms in the Oligocene-Miocene
biostratigraphic zones of the tropical areas of the
Pacific Ocean. Beih. zur Nova Hedwigia no. 45,
p.333-357.
- - , 1976: A review of the genus Bogorovia Jouse(Bacillariophyta). Botanical Journal, vol. I, p.
1232-1234. (in Russian)- - ed., 1977: Atlas of microorganisms in bottom
sediments of the Oceans, 196 p. Nauka, Moscow. (in Russian)Koizumi, I., 1972: Marine diatom flora of the
Pliocene Tatsunokuchi Formation in Fukushima
Prefecture. Trans. Proc. Palaeont. Soc. Japan,
N.S., no. 86, p. 340-359.
- - , 1973: Marine diatom flora of the Pliocene
Tatsunokuchi Formation in Miyagi Prefecture.
Trans. Proc. Palaeont. Soc. Japan, N.S., no. 91,
p.126-136.
- - , 1975a: Neogene diatoms from the western
margin of the Pacific Ocean, Leg 31, Deep Sea
Drilling Project. In, Karig, D.E., Ingle, J.e. Jr.,et al., In it. Rep. DSDP., vol. 31, p.779-819.
U.S. Govt. Printing Office, Washington, D.e.
- - , 1975b: Neogene diatoms from the northwestern
Pacific Ocean, Deep Sea Drilling Project. In,
Larson, R.L., Moberly, R. et al., Init. Rep.
DSDP., vol. 32, p. 865-889. U.S. Govt. Printing
Office, Washington, D.e.
- - , 1975c: Late Cenozoic diatom biostratigraphy
in the circum-North Pacific region. Jour. Geol.
Soc. Japan, vol. 81, p. 611-627.
- - , 1985: Diatom biochronology for late Cenozoic
northwest Pacific. Jour. GeoL Soc. Japan, vol.
91, p. 195-211.
- - , 1986: Pliocene and Pleistocene diatom datum
levels related with paleoceanography in thenorthwest Pacific. Marine Micropaleont., vol.
10, p. 309-325.
- - , 1990: Miocene to Pliocene marine diatoms
from Caleta Herradura de Mejillones section,
Chile. Rep. Andean Studies, Shizuoka Univ.
Spec. vol. 3, p. 17-22.
- - , 1992: Diatom biostratigraphy of the Japan
Sea: Leg 127. In, Piscitto, K.A., Ingle, J.e., Jr.,Von Breymann, M., Barron, J., et al., Proc. ODP,
Sci. Results, vols. 127/128 (Part 1), p.249-287.
College Station, TX (Ocean Drilling Program).
- - and Tanimura, Y., 1985: Neogene diatom biostratigraphy of the middle latitude western North
Pacific, Deep Sea Drilling Project Leg 86. In,
Heath, G.R., Burckle, L.H., et al., In it. Rep.
DSDP., vol. 86, p. 269-300. U.S. Govt. Printing
Office, Washington, D.e.
- - and Ujiie, H., 1976: On the age of the Nobori
Formation, Shikoku, Southwest Japan-particularly based on diatoms. Mem. Natn. Sci. Mus.,
Tokyo, no. 9, p. 61- 70.

615

Kulm, L.D., Thormburg, T.D., Schrader, H., Masias,A., Resig, J.M. and Johnson, L., 1981: Late
Cenozoic carbonate on the Peru continental
margin: Lithostratigraphy, biostratigraphy, andtectonic history. Geol. Soc. America Mem. 154,
p.469-507.
Maruyama, T., 1984: Miocene diatom biostratigraphy of onshore sequences on the Pacific side ofnortheast Japan, with reference to DSDP Hole
438A (Part 2). Sci. Rep., Tohoku Univ., Second
Ser. (Geology), vol. 55, p. 77-140.
- - , 1993a: Age determination and paleoenvironmental reconstruction based on diatom fossi Is.
Final Report on fossil Calyptogena from Ikego,
p.371-379. (in Japanese, title translated)- - , 1993b: Age determination and paleoenvironmental reconstruction based on diatom fossils (anadditional report). Final Report on fossil
Calyptogena from Ikego, p. 381-385. (inJapanese, title translated)
Monjanel, A.L., 1987; Oligocene to Holocene
diatoms from the North Atlantic and the western
Mediterranean: Biostratigraphy and paleoceanography. Doctoral thesis for L'Universite deBretagne Occidentale, 320 p. (in French withEnglish abstract)
Oda, M., 1986: Some aspects and problems concerned with microfossil biochronology for the
Neogene in central and northeast Honshu, Japan.
In, Nakagawa, H., Kotaka, T. and Takayanagi,
Y. eds., Kitamura Commem. Essays Geol., p.
297-312. (in Japanese with English abstract)
Pastor, P.R., 1991: La colecci6n de Diatomeas delInstituto Tecnol6gico Deo Mainero de Espaaa.
Boletin geologico y minero, no. 102-1, p. 19-92.
Powers, E.R., 1988: Diatom biostratigraphy andpaleoecology of the Miocene Pungo River Formation, Onslow Bay, North Carolina continental
shelf. Cushman Foundation Spec. Pub., vol. 25,
p.97-161.
Ross, R., Cox, E.J., Karayava, N.I., Mann, D.G.,
Paddock, T.B.B., Simonsen, R. and Sims, P.A.,
1979: An amended terminology for the siliceouscomponents of the diatom cell. Beih. zur Nova
Hedwigia, no. 64, p. 513-533.
Round, F.E., Crawford, R.M. and Mann, D.G., 1990:
The diatoms, 747 p. Cambridge Univ. Press,
Cambridge.
Sancetta, e.A., Carroll, S.E., Hillman, N.S., Janal,
M.J. and Van Couvering, J.A. eds., 1985: Catalogue of Diatoms, Book 1, The Ellis and Messina Catalogues of Micropaleontology, Micropaleontology Press, New York.
Schrader, H.-J., 1973: Cenozoic diatoms from thenortheast Pacific, Leg 18. In, Kulm, L.D., Von
Huene, R., et al., In it. Rep. DSDP., vol. 18, p.
637-797. U.S. Govt. Printing Office, Washin-

616

Yukio Yanagisawa

gton,D.C.
__, 1974a: Revised diatom stratigraphy of theexperimental Mohole Drilling, Guadalupe Sites.
Proc. California Acad. Sci., Fourth Ser., vol. 39,·p.517-562.
__, 1974b: Cenozoic planktonic diatom stratigraphy of the tropical Indian Ocean. In, Fisher,
R.L., Bunce, E.T., et al., Init. Rep. DSDP., vol.
24, p.887-967. U.S. Govt. Printing Office, Washington, D.C.
- - , 1976: Cenozoic planktonic diatom biostratigraphy of the southern Pacific Ocean. In, Hollister,C.D., Craddock, c., et al., Init. Rep. DSDP., vol.
35, p.605-671. U.S. Govt. Printing Office, Washington, D.C.
- - , 1977: Diatoms in DSDP Leg 41 sites. In,
Lancelot, E., Seibold, E., et al., lnit. Rep.
DSDP., vol. 41, p. 791-812. U.S. Govt. Printing
Office, Washington, D.C.
- - and Castaneda, J.c., 1990: The Ballena andDelfin wells off central Peru: revised ages. In,
Suess, E., Von Huene, R., et al., Proc. ODP, Sci.
Results, vol. 112, p.209-215. College Station,
TX (Ocean Drilling Program).
- - and Gersonde, R., 1978: Diatoms and silicoflagellates. In, Zachariasse, W.J. et al., eds.,
Micropaleontological counting methods andtechniques-an exercise on an eight meter sectionof the lower Pliocene of Capo Rosselo, Sicily.
Utrecht Micropaleont. Bull., vol. 17, p. 129-176.
Scientific Party, 1980: Init. Rep. DSDP., vols. 56 and57, 1417 p. U.S. Govt. Printing Office, Washington, D.C.
Simonsen, R., 1979: The diatom system: ideas on
phylogeny. Bacillaria, vol. 2, p. 9-71.
Taketani, Y., Aita, Y., Okada, H., Oda, M., Hasegawa, S., Maruyama, T. and Nemoto, N., 1986:
Microfossils from the Taga Group in the Futaba
area, Fukushima Prefecture, Japan. Res. Rep.,
Fukushima Museum, no. 12, p. I-53. (inJapanese, title translated)- - , - - , Ono, T., Okada, H., Hasegawa, S., Maruyama, T., Nemoto, N., Kurihara, S. and Takayanagi, Y., 1990: Geologic ages and sedimentary environment of the Neogene sequence in the
Joban area, Japan. Res Rep., Fukushima
Museum, no. 20, p. 1-99. (in Japanese, title
translated)
Watanabe, M., 1990: Stratigraphy of the Neogene
sequence in the Himi-Nadaura area, Toyama

Prefecture, central Japan-with special reference
to the hiatus between the Sugata Formation andoverlying formations-. Jour. Geol. Soc. Japan,
vol. 96, p. 915-936. (in Japanese with English
abstract)
Yanagisawa, Y., 1987: Age assignments of dredge
and piston core samples based on diatom biostratigraphy. CCOP Tech. Bull., vol. 19, p. 7387.
__, 1990a: Diatom biostratigraphy of the Neogene
Sendai Group, northeast Honshu, Japan. Bull.
Geol. Surv. Japan, vol. 41, p.I-25. (inJapanese with English abstract)- - , 1990b: Age of fossil Argonautidae (Cephalopoda) from Hokuriku Province (central
Honshu, Japan) based on diatom biostratigraphy. Bull. Geol. Surv. Japan, vol. 41, p.115127. (in Japanese with English abstract)- - , 1993: Thalassiosira mizunamiensis Yanagisawa sp. nov., a new Thalassiosira species fromthe early Middle Miocene Oidawara Formationin Mizunami area, central Japan. Diatom(Japanese Jour. Diatomology), vol. 8, p.43-49.
- - , in prep. a: Cenozoic diatom genus Rosseilla
Desikachary et Maheshwari: an emended
description. (submitted to Trans. Proc.
Palaeont. Soc. Japan. N.S.)- - , in prep. b: Cenozoic diatom genus Bogorovia
Jouse: an emended description.
- - , in prep. c: Phylogeny and evolution of the
diatom genera Rossiella Desikachary et Maheshwari, Bogorovia Jouse and Koizumia Yanagisawa.
- - , Kobayashi, 1., Takeuchi, K., Tateishi, M.,
Chihara, K. and Kato, H., 1986: Geology of the
Ojiya ditrict, Geological Survey of Japan Quadrangle Series (Scale I: 50,000), 177 p. (inJapanese with English abstract)- - , Nakamura, K., Suzuki, Y., Sawamura, K.,
Yoshida, F., Tanaka, Y., Honda, Y. and Tanahashi, M., 1989: Tertiary biostratigraphy and subsurface geology of the Futaba district, Joban
Coalfield, northeast Japan. Bull. GeoL Surv.
Japan, vol. 40, p.405-467. (in Japanese withEnglish abstract)- - , Tanimura, Y. and Koizumi, 1., 1991 : Cenozoic
diatoms. In, Palaeontologica Society of Japaned., Glossary of Palaeontology, plate 24. Asakura Shoten, Tokyo.

Ajigasawa ~7~, Ajigaura Ililf¥=77m, Akaishi $:0, Ao 1lilJ~, Dainenji *~"lf, E~betsu
JtllU, Endo Jt~, Futaba .5ll(~, Himi 7.KJi!., Hirono JA!I!f, Ikego rtH-=f, Isozaki li1!!Ufilf, Iwaki
ph ~, Iwanuma :'51tl, Kamogawa iI!\11;JII, Maido .P, Matsushima f)}£, Mizunami Jffij~,
Nabuto 11t7-.:, Nakayama .pLl./, Nishimyo ~-1:i, Nobori~, Oidawara ~f£€, Omatsuzawa

977.

Diatom genus Koizumia

617::kf~iR, Otokawa it}ll, Sado f6::i1t, Sendai {llJiJ, Shosanbetsu fJJw55U, Sumon '<Tr~, Tatsno-

kuchi ~o)D, Tomioka'MllilJ, Yotsukura 1Z!3~, Zushi)gr.

~~1t~~~~!ijJO)®T~ Ko;zumia I/J.: 1tE~~~J!~0)~IM Koizumia ~, K. tatsunokuchiensis (Koizumi) Yanagisawa, K. adaroi (Azpeitia) Yanagisawa:l3 J; rJ K. akibae
Yanagisawa 0) 3 U!~~I'::~.lL l t.:. ;;$:I/J. f;l:, ili:m:0) Rossiella 1/J.:l3 J; rJ Bogorovia 1M I'::{~.oiJ~,c' IJ M:~ (marginal ridge) O)IM'\iJ{§fjj~~O)m~I.::Nt:li'L.o;:. t, ~mJciJ;1;J]m"U:l3
J; rJ~:7E:"U ~{'F.o ;:. i::tJ' t'0)5!R'f!ffJ'*;'~ I.:: J; -::> l, :c h 0 O)IM t W!I'lI!'tifI':: IR55U ~ h.o. ;;$:
IM~mRlGT.o 3U!f;l:, ~)-rht>~#Jj'IiU!l', j:t ll,*_J§r:f:lh~O)t&J¥*td;l:OO~:f~H.::~i£:T.o iJ;, jf,?:'F~I':: f;l:YfJ' ~). ;:. 0) ,~l' t> ;;$:IMf;l:, ~;;$:I¥JI.::jf,?:'F'Iil:~*- ]l!r.MiH.::)j-lIJ0) ,*{j'~fi!f-:J Rossiella 1/J.:l3 J; rJ Bogorovia 1M t f;l:~ <~fJ'.o. Koizumia 1M f;l:,t'lJ M:~
1'::J;-::>l:R~)i1i7\M1*~{'F.o;:. t, apical pore field ~fi!f-:J;:' t, ~ 01.::;@tfBU'Bt:I':: I -:JO)Jg
i7\~~~fi!f-:J;:' tfJ't'0)~~iJ'0, ;f-7 r ~7fiH.::I/J.T.o t>O)th-0h.o.
:fPIJiR$xm:m:

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 176, pp. 618-637, 7 Figs., December 30, 1994

978.

CARBONIFEROUS FORAMINIFERS FROM THE EXOTICLIMESTONE BLOCKS IN THE ITSUKAICHI DISTRICT,SOUTHERN KANTO MOUNTAINS, JAPAN*
FUMIO KOBAYASHI
Institute of Natural and Environmental Sciences, Himeji Instituteof Technology, Sanda, Hyogo, 669-13

Abstract. Sixty-five species referable to 36 genera of Carboniferous foraminifers are
discriminated from the exotic limestone blocks embedded in the Jurassic accretionary
complexes of the Itsukaichi district, southern Kanto Mountains. These foraminifers are
Eostaffella, Profusulinella, and many others which have not yet been described in the Kanto
Mountains. Endothyra igoi, Eostaffella kamiyozawensis, Profusulinella hinodensis andPseudoendothyra musashiensis are newly proposed herein.
Key words. Carboniferous foraminifers, exotic limestone blocks, Jurassic accretionary
complexes, Itsukaichi, Kanto Mountains

yield more than 100 species of foraminifers
ranging in age from late Early Carboniferous
to Late Permian. The Carboniferous limestone blocks contain such primitive
fusulinaceans as Eostaffella, Profusulinella,
Akiyoshiella, and Pseudostaffella, and various
forms referable to Endothyridae and otherfamilies. Most of them are rarely known
from the Kanto Mountains and Outer Zone ofSouthwest Japan.
Late Paleozoic foramininifers have been
inactively investigated recently in comparison
with the peak time of the 1950's and 1960's inJapan. Collision-accretion tectonics and the
1980's radiolarian studies reveal that the Late
Paleozoic foraminifer limestones are exotic tothe surrounding arenaceous and pelitic rocks
and are inappropriate as an instrument forconsideration of age and structure of accretionary complexes. On the other hand,the fauna and facies of the limestones andother associated rocks, widely distributed in
the Japanese Islands, are an important sourceof information available for reconstructionsof the paleobiogeographic province and theIntroduction

Fusulinacean limestones in the Kanto
Mountains are mostly Middle Carboniferous
to Middle Permain in age (e.g. Huzimoto,
1936; Morikawa, 1955; Ishii, 1962;
Kobayashi, 1988). Lower Carboniferous
and Upper Permian limestones are rare inthese mountains. Igo and Kobayashi (1974,1980) reported Carboniferous limestones
from 12 localities in the Itsukaichi district,southern Kanto Mountains. They described
Namurian conodonts and corals from nodular or lenticular limestones and cherts fromsome of these localities, and briefly noted theoccurrence of such primitive fusulinaceans as
Millerella, Eostaffella, and Profusulinella.
Subsequently, these limestones and cherts
have been considered to be exotic blocks
embedded in the Jurassic accretionary complexes (Takashima and Koike, 1984; Ozawa
and Kobayashi, 1986; Sakai, 1987).
Limestone blocks in the Itsukaichi district'Received March 14, 1994; accepted June 8, 1994
618

978.

Carboniferous foraminifers from Itsukaichi District

travel history of the lost oceanic plate.
This paper announces the occurrence ofCarboniferous foraminifers from the limestone blocks embedded in the Jurassic accretionary complexes of the Itsukaichi district. Eight species, including 4 new, aredescribed. All the specimens illustrated inthis paper are stored in the collection of theDivision of Earth Sciences, Museum of
Nature and Human Activities, Hyogo.
I am grateful to Professor Hisayoshi Igo of
the University of Tsukuba for his criticalreading of manuscript and valuable advice.

Geologic setting
Carboniferous foraminifers in the southern
Kanto Mountains have been described orillustrated from the Raidenyama Paleozoic
Belt (Huzimoto, 1932) or the Kitaosogi Formation (Ozawa, 1975) west of Ome(Huzimoto, 1936: Ozawa, 1975), and fromthe Shiromaru Paleozoic Belt (Huzimoto,1932) or the Ogawadani Formation (Ozawa
and Kobayashi, 1986) west of Itsukaichi(Huzimoto, 1936; Kobayashi, 1988). Additionally, Igo and Kobayashi (1974) showedrather extensive distribution of Carboniferous
limestones in the Itsukaichi district. F ossiliferous Carboniferous limestones have beenreported at 36 localities, including 12 by Igo
and Kobayashi (1974). Among them, 27 areassignable to the Kamiyazawa Formation, 5
to the Takamizuyama Group, and 4 to the
Shomaru Formation (Figure 1) based on thesubdivision of the Jurassic accretionary complexes by Ozawa and Kobayashi (1986).
However, the subdivision in the Itsukaichi
district varies among authors (Takashima andKoike, 1984; Ozawa and Kobayashi 1986;
Sakai, 1987).
According to Ozawa and Kobayashi(1986), the Kamiyazawa Formation is distinguished from the Shomaru Formation by thedifference of chronologic distribution of
exotic blocks and age of the surrounding
pelitic rocks. On the basis of distribution,619

geologic structure and lithologic assemblages,
the Takamizuyama Group forms a nappeoverlying the Kamiyozawa, Shomaru and
Kawai Formations, which constitute theMusashi Group, and the Nishitama Group.
The Nishitama Group in the Itsukaichi district is a coherent stratigraphic unit of theUpper Permian to Upper Triassic, partly ranging to Lower Jurassic, and yields such diagnostic index genera as Palaeofusulina,
Ophiceras, HaloMa, Monotis and manyothers. Late Paleozoic foraminiferal limestones are entirely lacking in the Kawai
Formation.
Limestones of the Kamiyozawa andShomaru Formations are diverse in lithologies, ages, forms, sizes, chaotically embedded within sheared pelitic rocks. Exotic
blocks of the Jurassic Torinosu-type limestone are included in the Kamiyozawa Formation. Pillow lava and mafic hyaloclastite
enclosing numerous small blocks of limestone
are also observable. Most of the Paleozoic
limestones are poor or lacking in fossils, andconsist of fine-grained packstone. Occasionally, they suffer from weak dolomitization.
Occurrence of well-preserved foraminifers islimited to relatively coarse-grained packstone
and grainstone containing various kinds offossils, especially crinoids and algae.
Exotic blocks of the Takamizuyama Groupare characterized by laterally well-traceable,highly thick, bedded cherts. Two different
kinds of limestones are recognizable in thisgroup. One is nodular or lenticular limestones, which are embedded within basaltic
pyroclastics and lava situated at the base of
thick cherts. In places, they are prolific in
conodonts in addition to megafossils, as indicated by Igo and Kobayashi (1974) andothers. The other is thin-layered limestones
interbedded with cherts. Those exposed
around Mts. Hinode and Asou, and Mitake
Railway Station suffer remarkable dolomitization, some of them being altered to dolostone. These two types of limestones are best
displayed at Mitsuzawa, about 3 km NW of

620

Fumio Kobayashi

Figure 1. Gelogic map of the Itsukaichi district indicating fossil localities studied herein. I, 2, 5 :Musashi Group (\: Kamiyozawa Formation; 2: Shomaru Formation; 5: Kawai Formation). 3:
Takamizuyama Group. 4: Nishitama Group. 6: Tamagawa Group. 7: Neogene formations. 8:
Quaternary deposits.

Musashi-itsukaichi Railway Station (Igo andKobayashi, 1974).
Most species of the Carboniferous foraminifers in the Itsukaichi district occur inthe Kamiyozawa Formation, yielding such
pnmltlve fusulinaceans as Eostaffella,
Profusulinella, A kiyoshiella and Pseudostajftlla, and various forms referable to theEndothyridae and other families (Table I).
They are rarely known from the Kanto Mountains and Outer Zone of Southwest Japan.
Obsoletes obsoletus (Schellwien), Fusiella sp.
and Eoschubertella sp. are restricted to the
Shomaru Formation. Carboniferous as well
as Permian foraminifers are scarce in the

Takamizuyama Group. Some species of
Eostajftlla, En do thyra and others are yieldedby the limestones in which two Namurian
conodont assemblages of different ages are
discriminated (Igo and Kobayashi, 1974).

Systematic description
Superfamily Endothyracea Brady, 1884
Family Endothyridae Brady, 1884
Genus Endothyra Phillips, 1846
Endothyra igoi Kobayashi, n. sp.
Figures 3-1-7

Materials studied.-About 200 variously

978.

Carboniferous foraminifers from Itsukaichi District

Table 1. Carboniferous foraminifers of the Itsukaichi district.
those in Figure I.

Locality numbers correspond to

Kamiyozawa Formation
Tuberitina spp.
Tuberilinidae, gen. and sp. indet.
Pseudoammodiscus sp.
Pseudoglomospira sp.
P. ? sp.
Quasilituotuba sp.
Planoarchaediscus ? sp.
Eo/asiodiscus donbassicus Reyllinger
Climacammina sp. A
C. sp. B
C. sp. C:x::x: x: : xl

:x: x:

Takamizu Shomyama Gr. aru F:xlx:x:x:x;x x; x: x:: : : x;

::

::

• x,
, x,

: :
'x,

: : : :xx: : : x
I

: Xi

:X;

:x:

:x:

: x:
: :

:x:

:x:

:x
:x

: x;

C.~D

Pa/aeotextularia sp. A
P. spp.
Palaeolexlulariidae, gen. and sp. indet.
Biseriella kamensis (Reyllinger)
B. sp.
G/obivalvulina sp. A
G. sp. B
G. spp.
G/omos/iiroides sp.
Planoendothyra sp. A
P. sp. B
P. sp. C
Endothyra igoi, n. sp.
E. sp. A
E. sp. B
E. spp.
Bradyina sp. A
B. sp. B
B. ? sp.
Tetrataxis sp. A
T. sp. B
T. sp. C
Seminovella sp.
Mediocris breviscula (Ganelina)
Eostaffella etoi ala
E. kamiyozawensis, n. sp.
E. yowarensis (ala)E. spp.
Mil/erella sp.
Ozawainella sp.
Eoschubertella SP.
Fusiella sp.
Schubertella sp.
Akiyoshiella ozawai Toriyama
Beedeina higoensis (Kanmera)
B. sp.
Fusulinella itadorigawensis Ishii
F. simplicata Toriyama
F. sp.
Obsoletes obso/etus (Schellwien)
Profusulinella daiyamensis Hasegawa
P. hinodensis, n. sp.
P. rhomboides (Lee and Chen)
Pseudostaffella kanumai Igo
P. composita Grozdilova and Lebedeva
Quasifusulina longissima (Moller)
Carbonoschwagerina sp.
Montiparus matsumotoi (Kanmera)
Triticites nakatsugawensis Morikawa
T. ozawai Toriyama
T. sp. A
T. sp. B
Pseudoendothyra musashiensis, n. sp.

621

:x

: x:

x: :x: x:Ix:x' : xl

: Ix:

:x:

: xl

:x: :

: x:

x: x:

: xl

: x:

: xl : :,x. x,: xl,, x,,
'x,

:x:
:
: x;

: : : x: x

: xI

::
: :

: :
: x: : x: x x: :
:x

x: x:

:x:

: x;

:x:

x:
:x: x: x:
:x

:x

x: x:
: x:

: : x;
: xl

x'

x: x:
:x

: :x:
:

: x:

: x: : x: x

1 XI

, x,
x,

:x
:x

: x;

:x:
x:
:x

:x:
:x:
x:
x:

,,x,,

, x,

: :

: : x;: x::x:x

Fumio Kobayashi

622

oriented specimens.

Diagnosis.-Large-sized Endothyra having
shallowly depressed septal suture and welldeveloped secondary deposits, consists of streptospirally coiled inner 2 to 3 whorls andinvolute, partly evolute, planispirally coiled
terminal whorl.
Description.- Test discoidal with 4 whorls,
broadly rounded peri phery and umbilicaldepressions. Longer diameter of test about
0.57 to 0.77 mm. Proloculus, 0.04 to 0.06
mm in its outside diameter, followed by streptospirally coiled inner 2 to 3 whorls withabrupt changes of plane of coiling. The
terminal whorl is coiled planispirally andinvolute, partly evolute. Chambers a few inearly stages, 9 or 10 in the terminal whorl.
Wall usually with three layers, thin dark
outer and inner layers and their intermediate
thicker fibrous or alveolar layer in outerwhorls. Septa inclined anteriorly. Septal
sutures shallowly depressed. Secondary
deposits well developed on the chamber floor
and marginal part of chamber in form ofnodes, ridges or hooks.
Remarks.- The present new species resembles Endothyra excellens (Zeller) describedfrom the Clore Limestone of the type Chesterian of Illinois (Zeller, 1953) in mode of coiling, well-developed secondary deposits and alarge test. However, the former has morechambers in the terminal whorl, shallower
septal sutures and longer septa than does thelatter. This species is closely similar to
Endothyra rotayi Lebedeva originally described from the Lower Carboniferous of theKuznets Basin (Lebedeva, 1954), but differsfrom the latter in longer septa, more irregularand more rapid coiling and a larger ratio ofgreatest width to diameter. Endothyra
granularis Rozovskya from the Tula, Aleksin
and Mikhailov Horizons of the Russian Platform (Rozovskaya, 1963) is also similar to thepresent new species in some respects, but thelatter has a smoother test outline, more chambers and deeper septal sutures. En do thyra
mutabillis Reytlinger proposed from the Bashkirian of the central Volga area (Reytlinger,
1961) has a smaller test and smaller number ofchambers in the terminal whorl than thepresent new species.
Endothyra is most prolific in the Visean of
the Russian Federation and Ukraine (Bogush
and Yeferev, 1962; Rozovskaya, 1963). The
present new species seems to differ from the
Visean species of Endothyra by its larger test
and greater number of chambers.
Endothra sp. A in this paper is easily
distinguished from the present new species by
its smaller test and the slower expansion of~
Figure 2. 1-3. Tliberitina spp., lateral sections, I : Loc. 17; 02- 1342a, 2: Loc. 12; 02- 131 I, 3 :Loc. 25; 02- I 574, X 80. 4. Glomospiroides sp., lateral section, Loc. 3, 02- 1732, X 60. 5. Tuberitinidae
gen. and sp. indet., lateral section, Loc. 26, 02-1580, X 40. 6, 7. Eoiasiodisclis donbassiclis Reytlinger,
tangential sections, Loc.3, 6: 02-1761 b; X 80, 7: 02- I 733; X 100. 8, 14. Pselldoglomospira sp., lateral
sections, 8: Loc, I; D2-2198b, 14: Loc. 21;. D2-1266, x60. 9. QlIasilitllotliba sp., lateral section, Loc. 4,
D2-1779, X 60. 10,21-23. Pselidoammodisclis sp., 10: transverse section; Loc. 16: 02- 1282; X 60, 2123: tangential sections, Loc.27, 21: D2-1202a, x80, 22: D2-1209c; x80, 23: D2-1212; x60. 11.
Biseriella sp., lateral section, Loc.2, 02-2228, X 40. 12. GlobivalvlIlina sp. B, lateral section, Loc. 18, 021706, X 60. 13. PlanoarchaedisclIs? sp., axial section, Loc. 21, D2-1267b, X 80. 15, 16. Mediocris breviscliia (Ganelina), axial sections, 15: Loc. 3; D2-1728a; x80, 16: Loc. 27; D2-1208; X 100. 17-20.
Biseriella kamensis (Reytlinger), lateral sections, 17: Loc. 22; 02- 1464: X 80, 18: Loc. 21 ; D21272b; X 80, 19: Loc. 26; D2-1583; X 50, 20: Loc. 26; D2- I 633: X 60. 24-26. Endothyra sp. A, 24:
oblique section; Loc. 22; D2- 1463, 25 : axial section; Loc. 27; D2- 1204b, 26: tangential section; Loc.
27; D2- 1207a, X 60. 27,28. Planoendothyra sp. B, 27: sagittal section; D2-1258a, 28: tangential section; D2- 1258b, Loc. 2 I, X 60. 29. Climacammina sp. C, lateral section, Loc. 18, D2-1705c, X 50. 30.
Climacammina sp. A, longitudinal section, Loc. 17, D2-1342b, X 20. 31-34. Planoendothyra sp. A, 31 :tangential section; Loc. 27; D2-1207b; X 60, 32: sagittal section, Loc. 3; D2-1775d; X 50, 33: axial
section; Loc.26; D2-1588; x60, 34: tangential section; Loc.21; D-1259a; X 60. (All specimens inthis Figure are from the Kamiyozawa Formation)

978.

Carboniferous foraminifers from ltsukaichi District623

Fumio Kobayashi

624

each whorl.

Etymology.- This new species is named inhonor of Or. Hisayoshi Igo, Professor of the
University of Tsukuba in recognition of thehis eminent work on fusulinaceans of Japanand Southeast Asia.
Occurrence.-Common at Loc. 21, and rareat Locs. 3, 4, 15, 16, 21, 24, 26, 27, 28A.
Reg. numbers.-Holotype: D2-1267a(Figure 3-1), Paratypes: D2-1254 (Figure 32); D2-1272a (Figure 3-3); D2-1271 (Figure 3-4); 02-1267c (Figure 3-5); D2-1261(Figure 3-6); D2-1259b (Figure 3-7).
Genus Planoendothyra Reytlinger, 1959
Planoendothyra sp. A
Figures 2-31--34

Materials studied.-Four illustrated andadditionally several tens of variously oriented
specimens.
Description.- Test discoidal, broadly anddeeply umbilicated on both sides with shallowly depressed septal sutures, consisting of 4
whorls. Periphery and lateral sides broadly
rounded. Longer diameter of test about 0.63
to 0.80 (?) mm. Proloculus minute, about
0.03 mm in its outside diameter. Inner one
or two whorls streptospirally coiled, withsharp changes of plane of coiling, subsequentouter ones planispirally coiled and completely evolute.
Wall thin, microgranular, commonly
appears to be undifferentiated. Septa
medium to long, hooklike, curved anteriorly,

8 or 9 in the last whorl. Distinct secondary
deposits developed at basal and marginal
parts of chambers.
Remarks.- The present unnamed species ischaracterized by ~ thin wall, compared withsize of test, and distinct secondary deposits.
It is similar to Planoendothyra spirillinijormis(Brazhnikova and Potievskaya) illustrated in
pI. 19, fig. I by Potievskaya (in Wagner et al.
eds, 1979) from the Bashkirian of the Oonets
Basin in mode of coiling, broadly and deeply
umbilicated poles, thinner wall and development of secondary deposits, except for thelarger test of the former. Planoendothyra
mameti Igo and Adachi from the Ichinotani
Formation (Igo and Adachi, 1981) is alsosimilar to the present unnamed species, but
the latter has a larger test and more rapidly
expanding outer whorls.
Occurrence.-Rare to common at Locs.3,
4,21,26,27,28B.
Reg. numbers.-D2-1207b (Figure 2-31),
D2-1775d (Figure 2-32),02-1588 (Figure 233), D2-1259a (Figure 2-34).
Superfamily Fusulinacea von Moller, 1878
Family Ozawainellidae Thompson
and Foster, 1937
Genus Eostaffella Rauser-Chernousova, 1948

Eostaffella kamiyozawensis
Kobayashi, n. sp.
Figures 3-23--28

Materials studied.-Six illustrated specImens and several others.

~
Figure 3. 1-7. Endothyra igoi Kobayashi, n. sp., I, 3: axial sections; 2, 5: tangential sections; 4,
6: oblique sections; 7: sagittal section, 1,3-7: Loc. 21; 2: Loc.24, I: D2-1267a (holotype); 2-7: D21254: D2-1272a; D2-1271 : D2-1267c; D2-1261 ; D2-1259b (paratypes), I, 2, 4, 6, 7: X 60; 3, 5: X 50.
8-17. Eostaffilla yowarensis (Ota), 8-10,13,14: axial sections; 11,12,15: tangential sections; 16,17:
sagittal sections, 8-13, 15: Loc. 27; 14,16: Loc. 3; 17: Loc. 21,8: D2-1209a; 9: D2-1209b 2 IO: D21205; 11: 02-1206; 12: D2-1207c; 13: 02-1202b; 14: D2-1731; 15: D2-121Ia; 16: D2-1766; 17:
02-1269,8,9: x80; 10-15, 17: x60; 16: x50. 18-21. Eostaffella etoi Ota, 18-20: axial sections;
21 : sagittal section, Loc.3, 18: D2-1762; 19: D2-1760; 20: D2-1750; 21: D2-176Ia, x60. 22.
Bradyina sp. A, axial section, Loc. II, D2-1906, X 40. 23-28. Eostaffilla kamiyozawensis Kobayashi, n.
sp., 23, 24: sagittal sections; 25, 27, 28: axial sections; 26: tangential section, Loc. 4, 27: D2-1777(holotype), 23-26, 28: 02-1775a; D2-1776a; 02-1776b; D2-1775b; D2-1775c (paratypes), X 60. (Allspecimens in this Figure are from the Kamiyozawa Formation)

978.

Carboniferous foraminifers from ltsukaichi District

625

626

Fumio Kobayashi

Diagnosis.-Large-sized species of
Eostaffella characterized by a bluntly pointed
periphery, nearly straight lateral sides, somewhat protruded poles, asymmetrical, low andmassive chomata, and weak secondary
deposits in polar regions.
Description.-Shell large for the genus,
lenticular in shape with a bluntly pointed
periphery, straight to slightly convex lateralsides and somewhat protruded poles.
Mature shell of 5 to 6 volutions, and 0.32 to
0.38 (?) mm in axial lenghth, 0.72 to 0.83 (?)
mm in median width. Form ratio about 0.5.
Pro loculus small, spherical and 0.03 to 0.05
mm in its outside diameter. Inner one or
two volutions slightly askew to planispirally
coiled succeeding outer ones. The first to
fifth volutions of the holotype: 0.03,0.03,
0.05, 0.11 and 0.16 mm in half length; 0.04,
0.08,0.11,0.18 and 0.31 mm in radiusvecotor; 0.6, 0.4, 0.4, 0.6 and 0.5 in form
ratio, respectively.
Spirotheca rather thick for the genus, composed of three layers, a thin tectum and lower
and upper tectoria in outer volutions, but
undifferentiated in the first volution. Its
maximum thickess in the fifth volution about
0.02 mm in the holotype. Septa unfluted andslightly inclined anteriorly. Septal counts
from the first to fifth volutions 5 or 6, 10 or
II, II or 12, 13 to 16 and 19 (?), respectively.
Weak secondary deposits developed inpolar regions. Chomata asymmetrical, low
and massive. Tunnel angle variable in volutions as well as specimens, but less than 20
degrees in most of outer volutions.
Remarks.-Periphery, lateral sides andpolar regions of the present new species
appear to be more similar to Ozawainella
than to Eostaffella. However, this species is
assignable to Eostaffella based on poorly
developed chomata, a smaller shell, and fewer
septa and volutions. The present new
species is most similar to species of the
Eostaffella ikensis group such as E. ikensis
Vissarionova, E. ikensis tenebrosa Vissarionova and E. proikensis Rauser-Chernousova

in many respects, but the former differs fromthe latter Visean forms by its larger shell,
more number of volutions and more rapidly
expanded outer volutions. This new species
closely resembles Eostaffella pespicabila
Grozdilova and Lebedeva, which also
belongs to the Eostaffella ikensis group described from the Visean of the Perm district(Grozdilova and Lebedeva, 1954). However,E. pespicabila has poorly developed chomata
and prominent umbilicated depressions.
Three forms of Eostaffella mirijica Brazhnikova proposed from the Namurian of the
Dnieper-Donets Basin (Brazhnikova et al.,1967) are distinct from this new species inhaving a smaller shell, narrower tunnel andmore pointed periphery.
Eostaffella kamiyozawensis resembles
Eostaffella quasiampla Sheng, E. subsolana
Sheng and E. intermedia Sheng describedfrom the "Taitzeho" (Taizihe) Valley of
Liaoning, North China (Sheng, 1958). However, the present new species has a larger shelland longer radius vectors in the corresponding volution. This new species is also similar to Ozawainella japonica Sada from the
Akiyoshi Limestone (Sada, 1975), but thelatter has a straight tunnel, more massive
chomata and more septa.
Etymology.-Species name comes from thelocal geographical name Kamiyozawa, located northwest of Itsukaichi.
Occurrence.-Common at Loc.4.
Reg. numbers.-Holotype: D2-1777 (Figure 3-27), Paratypes: D2-1775a (Figure 323); D2-1776a (Figure3-24); D2-1776b(Figure 3-25); D2-1775b (Figure 3-26) ;D2-1775c (Figure 3-28).

Eostaffella yowarensis (Ota, 197 I)
Figures 3-8-17

Millerella yowarensis Ota, 1971, p. 66, 67, pI. 12, figs.
1-19; Ota, 1975, pI. IIE-4, figs. II a, lib (notdescribed, fig. Iia is same as pI. 12, fig. 8 of Ota,
1971); Sashida, 1981, p. 10, II, pI. 3, figs. 1-7;
Matsusue, 1986, pI. 6, figs. 13 (not described);
Veno, 1989, pI. I, fig. I7 (not described).

978.

Carboniferous foraminifers from Itsukaichi District

Millerella toriyamai Ota, 1971, p. 67, 68, pI. 13, figs. 115; Matsusue, 1986, pI. 6, fig. 14 (not described).
Eostaffella yowarensis (Ota), Ozawa and Kobayashi,
1990, pI. 2, figs. 1,2 (not described).

Materials studied.-Ten illustrated andseveral other specimens.
Description.-Shell lenticular to discoidal
with narrowly to broadly rounded periphery,straight to convex lateral sides and slightly
depressed umbilical regions. The first volution evolute, subsequent ones generally
involute, and the outermost one involute toslightlyevolute. Mature shell composed of 4
to 5 volutions gradually increasing in height.
Expansion of shell and outline of each volution vary considerably.
Length 0.18 to 0.24 mm, width 0.45 to 0.63mm, and form ratio 0.3 to 0.4 in 9 axial
sections. Proloculus minute, spherical and0.02 to 0.04 mm in outside diameter. Spirotheca commonly less than 0.01 mm in thickness, composed of a tectum, lower tectoriumand very thin, partly lacking, upper tectorium
in outer volutions. Septa plane and slightly
curved anteriorly. Septal count 14 or 15 in
the terminal volution. Chomata low andpoorly developed. Tunnel path narrow andgenerally straight, but highly irregular in
speClmens.
Remarks.- The species belonging to Millerella, as represented by the type species, havea completely evolute shell, while some species
referable to Eostaffella have an involute orpartly evolute last volution, such as E.
designata (Zeller), E. pinguis (Thompson), E.
pressa (Thompson), E. mutabilis RauserChernousova, and E. postmosquensis Kireeva.
Millerella yowarensis and M. toriyamai
were described from the same locality of the
Akiyoshi Limestone (Ota, 1971). Based on
the coiling of the shell, expansion of the outer
volutions, and other characteristics, they are
assignable to Eostaffella. The holotypes of
the two mentioned species are dissimilar in
the thickness of the spirotheca, shape of theperiphery, lateral sides and umbilication of
the poles. However, many specimens illus-

627

trated by Ota show wide vanatIOn and E.
toriyamai is considered to be conspecific with
E. yowarensis.
The Itsukaichi specimens are identical with
E. yo warensis , but they have a somewhat
smaller shell and thinner spirotheca than dothe original specimens. E. yowarensis differsfrom Eostaffella bigemmicula (Igo) in having
a larger shell. It is probably distinguishedfrom E. kanmerai (Igo) by the completely
invol ute coiling of the latter. This species
shows some resemblance to Eostaffella mixta(Rauser-Chernousova) and E. pseudostruvei(Rauser-Chernousova and Beljaev) var.
chomatifera Kireeva from the Bashkirian of
the Russian Platform and adjacent regions(Rauser-Chernousova et al., 1951) and
Onieper-Oonets Basin (ManukalovaGrebenyuk et al., 1969), respectively, butdiffers from the latter two in having thinnerspirotheca and obscure and discontinuouschomata.
Occurrence.-Common at Loc. 27 and rareat Locs. 3,15,21-24,26.
Reg. numbers.- 02-1209a (Figure 3-8),
02-1209b (Figure 3-9), 02-1205 (Figure 310),02-1206 (Figure 3-11), 02-1207c (Figure 3-12), 02-1202b (Figure 3-13), 02-1731(Figure 3-14), 02-1211a (Figure 3-15), 021766 (Figure 3-16),02-1269 (Figure 3-17).
Family Fusulinidae von Moller, 1878
Genus Profusulinella Rauser-Chernousova
and Beljaev, 1936
Profusulinella hinodensis
Kobayashi, n. sp.
Figures 4-3-7, 6-5

Materials studied.-Five illustrated andseveral other specimens.
Diagnosis.-Inflated fusiform to fusiform
Projuslinella, having unfluted septa throughout the shell, and a rather high irregulartunnel path.
Descripiton.-Shell inflated fusiform tofusiform in shape with a broadly archedperiphery, straight lateral sides and bluntlyFumio Kobayashi

628

pointed poles. Mature shell of 5 to 6 volutions, 1.34 to 1.68 mm in axial length and 0.83
to 1.l0mm in median width, giving a form
ratio of 1.5 to 1.9. The holotype of 5 Yz
volutions, 1.62 mm in axial length, 1.10 mmin median width, with a form ratio of 1.5.
Proloculus subspherical, small, and 0.07 to
0.09 mm in longer diameter, 0.08 mm in theholotype. Inner one or two volutions tightly
coiled, subsequent ones gradually increase inlength and width. The first to fifth volutionsof the holotype are: 0.06,0.12,0.34,0.55 and
0.73mm in half length: 0.08,0.12,0.19,0.32
and 0.47 mm in radius vector; 0.8,0.9, 1.8,
1.7 and 1.6 in form ratio, respectively.
Spirotheca very thin and probably
undifferentiated in inner one or one and ahalf volutions. Beyond the second volution,
spirotheca gradually thickened, composed ofa tectum and thin lower and upper tectoria.
Septa unfluted throughout shell. Septal
counts from the second to fifth volutions: II,
14,15 and 19 (?) in the specimen illustrated in
Figure 4-6, 10, 13, 15 and 18 in Figure 4-7.
Chomata low, gently sloping toward polar
regions in inner volutions, becoming higher
in tunnel regions of outer volutions. Tunnel
rather high, half to one-third as high as chambers. Tunnel path narrow in inner volutions, and highly variable in outer ones.
Tunnel angle of some specimens attains morethan 70 degrees in outer volutions.
Remarks.-Profusulinella hinodesis resembles P. fukujiensis Igo from the Ichinotani~

Formation (Igo, 1957) and P. beppensis Toriyama from the Akiyoshi Limestone (Toriyama, 1958). Many topotype specimensfrom Ichinotani and Akiyoshi are examined
for the sake of better understanding of theintraspecific variation of these two species(Figure 6). They show wide variation especially in size of shell, shape of lateral sides
and poles, and development of chomata.
The present new species can be distinguishedfrom P. fukujiensis in less prominentchomata, a larger shell and larger from ratio,
and from P. beppensis in weaker developmentof chomata, more slowly expanded outer
volutions, a smaller shell and larger form
ratio. Profusu lin ella omiensis Watanabe,
described from the Omi Limestone(Watanabe, 1974), has weakly fluted septa inthe polar regions, whereas septa of the present
new species are unfluted throughout shell.
P. hinodensis is easily distinguished from P.
daiyamensis Hasegawa originally describedfrom the Akiyoshi Limestone (Hasegawa,1967) in having slightly concave lateral sides
and by the smaller proloculus of the latter.
Profusulinella n. sp. ill ustrated by Ishii (1985)
from the Yura area, Kii Peninsula, is considered to be identical with the present new
species, but the former has not been described.
The present new species is allied toProfusulinella ovata Rauser-Chernousova
and P. aljutovica Rauser-Chernousova, bothof which were originally described from the

Figure 4. 1,2. Pseudostaffella composita Grozdilova and Lebedeva, I: axial section; 02-1978a;
X 50, 2: tangential section; 02-1978b; X 60, Loc. 5. 3-7. Profusulinella hinodensis Kobayashi, n. sp., 35: axial sections; 6, 7: sagittal sections, Loc. 6, 3: 02-1832 (holotype); 4-7: 02-1833; 02-1835; 021834; 02-1841 (paratypes), X 25. 8.9. Pseudostaffella kanumai Igo, axial sections, 8: Loc. I ; 022196; X 60, 9: Loc. 7C; 02-1808; X 30. 10, 11. Profusulinella rhomboides (Lee and Chen), 10: axial
section; 02-2195, II: tangential section; 02-2198a, Loc. 1, x25. 12-14. Akiyoshiella ozawai Toriyama,
12, 14: tangential sections; 13: oblique section, Loc.7B. 12: 02-1813a; 13: 02-1813b; 14 : 021813c, X 15. 15, 16. Fusulinella itadorigawensis Ishii, 15: axial section; 02-1905, 16: oblique section;
02-1904, Loc. II, x20. 17,18. Montiparus matsumotoi (Kanmera), axial sections, Loc. 12, 17,: 02-1305;
18: 02-1306,x 15. 19. Triticites ozawai Toriyama, axial section, Loc.19, 02-1556, X 10. 20,
Quasifusulina longissima (Miiller), axial section, Loc. 13, 02-1325, X 15. 21. Carbonoschwagerina sp.,sagittal section, Loc. 14. 02-1667, X 15. (All specimens in this Figure are from the Kamiyozawa Formation)

978.

Carboniferous foraminifers from Itsukaichi District629

Fumio Kobayashi

630

Lower Moscovian of Samara Bend (RauserChernousova, 1938). However, P. hinodensis differs from the former by its larger
pro loculus, more loosely coiled inner volutions and wider tunnel, and from the latter by
its more inflated shell. P. primitiva Grozdilova and Lebedeva from the Bashkirian of
the Kolva-Vishera region (Grozdilova andLebedeva, 1954) is also close to the present
new species. Some major differences
between the two species are that the former
has a smaller shell, narrower tunnel and morepointed axial ends. P. hinodensis is distinguished from P. decora Thompson and P.
munda Thompson described from theProjusulinella Zone of Texas (Thompson,1948) by its smaller shell, larger tunnel angles
and more irregular tunnel path.
Etymology.- This species is named for Mt.
Hinode, northwest of Itsukaichi.
Occurrence.-Common to rare at Loc.6.
Type specimens.-Holotype: 02-1832(Figure 4-3), Paratypes; 02-1833 (Figure 44); 02-1835 (Figure 4-5) ; 02-1834 (Figure4-6); 02-1841 (Figure 4-7).
Genus Obsoletes Kireeva, 1950
Obsoletes obsoletus (Schell wien, 1908)
Figures 7-8-14
Fusulina obsoleta Schellwien, 1908, p. 167, 168, pI. 19,
figs. 5-7.
Neofuslinella obsoleta (Schellwien), Lee, 1927, p. 18,
19, pI. 2, fig. 19.
Fusulinella obsoleta (Schellwien), Putrja, 1940, p. 5456, pI. 2, figs. 6-9.
Protriticites obsoletus (Schellwien), Putrja, 1948, p. 94,
pI. 1, figs. 7; Rozovskaya, 1950, p. 10, 11, pI. 1,
figs. 1-4; Da and Sun, 1983, p. 38, 39, pI. 7, fig. 2.
Obsoletes obsoletus (Schellwien), Rauser-Chernousova and Fursenko, 1959, pI. 7, fig. 8 (same as
pI. 1, fig. 2 of Rozovskaya, 1950); Rozovskaya,
1975, pI. 12, figs. 5, 6 (fig. 5: same as pI. 19, fig. 7of Schellwien, 1908; fig. 6: same as pI. 1, fig. 2of Rozovskaya, 1950); Niikawa, 1978, p.562,
563, pI. 12, figs. 1,2: Ozawa and Kobayashi,
1990, pI. 3, figs. 16-18 (not described); Ozawa,
Kobayashi and Watanabe, 1991, Fig. 3. 1,2(same as pI. 3, figs. 16, 18 of Ozawa and Kobayashi, 1990).

Obsoletes obsoleta (ScheJlwien), Loeblich andTappan, 1988, pI. 267, figs. 10-12 (same as pI. 19,
figs. 6, 7, 5 of ScheJlwien, 1908).
Protriticites obsoletus cylinidrica Da, in Da and Sun,
1983, p. 38, pI. 7, fig. 1.
Protriticites atf. obsoletus (Schellwien), Sheng, 1958,
p. 36, 37, 95, 96, pI. 10, fig. 12.
? Obsoletes cf. obsoletus (Schellwien), Ueno, 1991, p.
818, figs. 4-9-13.
non. Protriticites obsoletus (Schellwien), Chen andWang, 1983, p.40, pI. 5, figs. 8, 9, 12.

Materials studied.-Five axial and twosagittal sections illustrated.
Description.-Shell subcylindrical to elongate fusiform with a broadly arched periphery, straight to slightly convex lateral sides
and rounded poles. Mature shell of 5 to 6
volutions, 5.09 to 5.62 (?) mm in axial lengthand 1.45 to 1.55 mm in median width. Formratio 3.5 to 3.6.
Proloculus spherical to subspherical, 0.08
to 0.12 mm in outside major diameter. Inner
three volutions fusiform and tightly coiled.
Outer two to three volutions, elongate fusiform to subcylindrical and loosely coiled
compared with inner cones. The first to fifth
volutions of the specimen shown in Fig. 7-8 :
0.12,0.41,0.75,1.36 and 2.59 mm in half
length; 0.11, 0.18, 0.32, 0.50 and 0.85 mm inmedian width; l.l, 2.3, 2.4, 2.7 and 3.0 inform ratio, respectively.
Spirotheca thin, composed of a tectum andlower and upper tectoria in inner three volutions. Lower tectorium partly seems to bediaphanotheca. In outer volutions, spirotheca consists of a tectum and protheca withalveolar structure. Upper tectorium obscureor lacking. Thickness of spirotheca from thefirst to fifth volutions of the specimen shownin Figure 7-8: 0.013,0.015,0.023,0.023 and0.028 mm, respectivey.
Septa weakly fluted in polar and axial
regions. Septal counts of the first to sixth
volutions of the specimen shown in Fig. 713: 8, II, 13, 15, 16 and 21, respectively.
Chomata massive, asymmetrical, nodelike
to hooklike, one-third to two-thirds as highas chambers, but discontinuous and poorly

978.

Carboniferous foraminifers from Itsukaichi District

developed in the terminal volution. Tunnel
angle 20 to 35 degrees in inner volutions, buthighly variable and occasionally attains morethan 50 degrees in outer ones. Tunnel path
not straight.
Remarks.- The present specimens haveabout twice as large a shell and more strongly
fluted septa than the original ones describedfrom the Upper Carboniferous of the Donbass (Schellwien, 1908). However, they present striking similarities in other characterssuch as thin spirotheca and massive chomata.

631

The Itsukaichi specimens bear the closest
resemblance to those described from theUpper Carboniferous of the Moscow Basin by
Rozovskaya (1950) .
This species shows considerable but continuous variation . However, there are remarkable differences between the Akiyoshi specimens described by Ueno (\991) a nd previously described ones in thickness of spirotheca,
septal fluting and development of chomata.
It is doubtful whether the Ueno's specimens
are referable to the present species and assign-

Figure 5. 1. Millerella sp., axial section. Loc.27. 02- 1204c. x 60. 2- 9. Pselldoen~othyra ';lIs?a~shiensis Kob ayas hi , n. sp. , 2- 7 : ax ial sections: 8.9: sagittal secti o ns. 2- 4, 6- 9: Loc. 3 , ). Loc. _7 , : .
02 - 1746 (holotype) ; 3- 9: 02 - 1735 ; 02 - 1737; 02 - 121Ib : 02 - 1738; 02 - 1756 ; 02- 1728b; 02- 17)9
(paratypes) , 2, 4, 6- 9: x 50 ; 3, 5: X 60. 10, 11. S chllbertella sp., 10 : aX ial sect lo~ ; Loc: 12 ; 02- 1299:
II: sagittal section ; Loc. 13, 02- 1318, x 40. 12- 18. Trlllcites nakatsllgawensls Monkaw.a, 12 - 1~.
axial sections; 17,18: sagittal sections, 12, 13, 15 - 17: Loc. 13 ; 14,18: Loc. 18, 12. 02- 1321 , 13. 0_1324 ; 14: 02- 1705a ; 15 : 02 - 1322a 16: 02 - 1319 ; 17: 0 2- 1322b ; 18: 02 - 1705b, X IS .. 19,20.
Triticires sp., ax ial sections, Loc. 14, 19 : 02- 1669 ; 20: 0 2- 1668, X 15. (All specimens Ii1 thiS Figure
are from the Kamiyozawa Formation)

Fumio Kobayashi

632

able to Obsoletes based on the dissimilaritiesof these diagnostic characters. Three specimens described from the Maping Limestoneof Guangxi by Chen and Wang (1983) do notbelong to this species. These have rather
symmetrical chomata, straight tunnel path ,and thicker spirotheca in o uter volutions,compared to the original as well as to otherpreviously described materials.
Occurrence. - Common to rare at Loc. 36.
Reg. numbers .-02-3163a (Figure 7-8) ,02- 3169 (F igure 7-9), 0 2-3 17 3 (Figure710), 02-3172a (Figure 7- 11), 02- 3174a (Figure 7- 12), 0 2- 3175 (Figure 7-13), 02- 3164a(Figure 7- 14).

present form is: undiffereniated in the first
vol uti on; composed of a tectum , thicker
lower tectori urn showi ng appearance ofprotheca and thinner, occasionally indistinct,
upper tectorium in the second and third ones ;and made up of a tectum and finely a lveolar
keriotheca in the succeeding ones. The Itsukaichi specimens closely resemble Montiparus

Family Schwagerinidae Dunbarand Henbest, 1930
Genus Montiparus Rozovskaya, 1948
Montiparus matsumotoi (Kanmera, 1955)
Figures 4- 17, 18

Triticites matsumotoi Kanmera, 1955, p. 184, 185, pI.
II figs. 6- 25 ; Choi , 1972, p.483- 486, pI. 7, figs.
1- 9 ; Ota, 1975, pI. IIE- 4, figs. 9a, 9b (not described).
Protriticites (Protriticites) malsumotoi (Kanmera);
Ozawa, 1975, pI. 8, figs . 29- 31 (not described).
Prolriticites aff. malsumotoi (Kanmera); Yamagiwa
and Kubota, 1980, figs. 1- 3 (not described).
Triticites malsumotoi kattoi Suyari , 1962, p. 15 , 16,
PI. 5, figs. 1- 3.
Triticites malsumotoi suitaensis Suyari , 1962, p. 17,
18 , pI. 5, figs. 4-6.
Montiparus matsumoloi (Kanmera): Ozawa andKob ayash i, 1990 pI. 4, figs. 4, 5 (not described) ;Ozawa, Kob ayas hi and Watanabe, 1991 , figs. 3- 7,
8 (not described, fig. 3- 8 is same as pI. 4, fig . 5 of
Ozawa and Kobayashi , 1990).

Remarks.-Spirothecal structure of the~

Figure 6. 1,2. Profusulinella beppensis Toriyama, topotype specimens from the Akiyoshi Limestone. 3,4. Profusulinella fukujiensis 19o, topotype
specimens from the lchinotani Formation. 5.
Profusulinella hinodensis Kobayashi , n. sp. , holotype
speci men from the Kamiyozawa Formation. All
are X 25.

Figure 7. 1, 2. Endothyra sp. B, I : tangential section ; 02- 3171 , 2: axial section; 02- 3174b,
Loc. 36, X 60. 3, 4. Bradyina sp. B, 3: axia l section ; 02- 3172b, 4: lateral section ; 0 2- 3164b, Loc.
36, .x 30. 5. Climacammina sp. 0, longitudinal section , Loc. 36, 02- 3167, x iS. 6. Fusiella sp. , axial
section , Loc.36, 0 2- 3163b, x 40. 7. Eoschubertella sp., axial section, Loc. 36, 02- 3165, x 60. 8- 14.
Obsoletes obsoletus (Schellwien), 8- 12 : ax ial sections, 13, 14: sagitta l sections , Loc. 36, 8 : 02- 3163a ; 9:
02- 3169; 10 : 02- 3173 ; II: 02- 3 172a; 12: 02- 3174a ; 13: 02- 3175 ; 14: 02-3 164a, 8A , 9A, 10- 12,
13A, 14: X II ; 8B, 9B, 13B: X 40. 15. Beedeina sp., sagittal section, Loc. 34, 02- 3084, x IS. 16.
Triticites sp. B, axial section , Loc. 32, 02- 3221, X 15. (All specimens in this Figure are from the Shomaru
FormatIon, except for 16 from the Taka mizuyama Group)

978.

Carboniferous foraminifers from Itsukaichi District633

Fumio Kobayashi

634

matsumotoi (Kanmera) in tightly coiled inner
volutions, massive chomata and weakly fluted
septa in polar regions, in addition to spirothecal structure; nevertheless, the terminal
volution is incompletely preserved. Although the original specimens from the
Yayamadake Limestone were assigned to thegenus Triticites (Kanmera, 1955), the expansion of the shell, devolpment of chomata, andthickness and composition of the spirothecaof this species are more like Montiparus than
Triticites.
Two subspecies proposed by Suyari (1962)
from Shikoku are considered to be synonymous with Montiparus matsumotoi, because
the Shikoku specimens are not clearly marked
off from the original Yayamadake ones, there
being only slight differences of developmentof chomata, form ratio, and other features.
Occurrence.-Common to rare at Loc. 12.
Reg. numbers.-02-l305 (Figure 4-17),
02-1306 (Figure 4-18).
Family Staffellidae Miklukho-Maklay, 1949
Genus Pseudoendothyra Mikhaylova, 1939

Pseudoendothyra musashiensis
Kobayashi, n. sp.
Figures 5-2-9

Materials studied.-Eight illustrated specimens.

Diagnosis.-Pseudoendothyra with alenticular shell, weakly recrystallized in its
outer part and more remarkably recrystallized
in its inner part, consisting of 4 to 5 volutions,
minute proloculus, rather thick spirothecacompared with size of shell and indistinct
chomata.
Description.-Shell medium to small for the
genus, lenticular in shape, weakly recrystallized in its outer part and more remarkably
recrystallized in its inner part. Peripherybluntly pointed to narrowly rounded, lateralsides convex to nearly straight, polar regions
almost parallel-sided with shallow umbilicaldepressions. Coiling subinvolute throughout growth. Mature specimens of 4 to 5

volutions, 0.27 to 0.38 mm in axial length,0.66 to 0.77 mm in median width, giving aform ratio of 0.4 to 0.6. Proloculus minuteand spherical. Inner one to two volutions
tightly coiled compared with the subsequentgradually expanding ones. Prolocular size,
half length and radius vector of each volution
not exactly measured.
Spirotheca rather thick compared with sizeof shell and composed of a tectum and inner
thick translucent layer in outer vol utions.
Septa recrystallized as well as spirotheca,
unfluted and curved anteriorly. Chomata
indistinuct, rudimentarily developed at bothsides of a low, straight and narrow tunnel.
Remarks.- The present new species resembles Pseudoendothyra yakoyamai (Sada)
from the Profusulinella Zone of the Taishaku
Limestone (Sada, 1972) in shape and degreeof recrystallization of the shell. However,the former has a smaller shell and fewer
volutions. Although the radius vector andhalf length of the present new species are notexactly measured, they are likely to be smaller
than the corresponding volutions of P. yokoyamai (Sada).
Various forms of Pseudoendothyra, assigned to 14 species and six subspecies, aredescribed from the Middle Visean to Lower
Moscovian of the Moscow Basin and elsewhere (Rozovskaya, 1963). Some of them
are closely similar to the present new species,
but P. musashiensis has a more remarkably
recrystallized shell, especially in its inner partand indistinct chomata. By its smaller shell
for about the same number of volutions, thisspecies is apparently distinguished from
Pseudoendothyra mathildae (Outkevich)originally described from the Kasimovian of
the Middle Urals (Outkevich, 1934) and P.
vlerki (Ginkel) and its allied species described from the Vereyan of the Cantabrian
Mountains, Spain (Ginkel, 1965).
Etymology.-Species name is derived fromthe ancient geographical name, Musashi, for
the western part of Tokyo Prefecture.
Occurrence.-Common at Loc.3 and rare

978.

Carboniferous foraminifers from Itsukaichi Districtat Locs.4 and 27.
Reg. numbers.-Holotype: 02-1746 (Figure 5-2), Paratypes: 02-1735 (Figure 5-3) ;02-1737 (Figure 5-4); 02-1211b (Figure 55); 02-1738 (Figure 5-6); 02-1756 (Figure5-7); 02-1728b (Figure 5-8); 02-1759(Figure 5-9).

References cited
Bogush, O.I. and Yeferev, O.V., 1962: Foraminiferand stratigraphy of the Carboniferous depositsof Karatau and Talas Alatau. Inst. Geo!.
Geofiziki, Akad. Nauk SSSM, Siberskoe otdelenie, 234 p., 9 pIs. (in Russian)Brazhnikova, N.E., Vakarchuk, G.!., Vdovenko,
M.V., Vinnichenko, L.V., Karpova, M.A.,
Kolomiets, Va, I., Potievskaya, P.D., Rostovtseva, L.F. and Shevchenko, G.D., 1967: Microfaunal reference horizons of the Carboniferous and Permian deposits of the Dnieper-Donets
Depression. Kiev: Inst. Geo!. Nauk, Akad.
Nauk Ukrainskoy SSR, 224 p., 59 pIs. (in Russian)Chen, X and Wang, J., 1983: The fusulinids of theMaping Limestone of the Upper Carboniferous
from Yishan, Guangxi. Palaeont. Sinica, N.
Ser. B, no. 19, p. 1-139, p!. 1-25. (in Chinesewith English summary)Choi, D.R., 1972: Discovery of the Ural ian
fusulinids from the Upper Permian conglomerate
in the southern Kitakami Mountains, Japan.
Jour. Fac. Sci., Hokkaido Un iv. , Ser. 4, vol. 15,
nos. 3-4, p. 479-491, pIs. I, 2.
Da, Y.D. and Sun, Q.L., 1983: Fusulinida. In,
Xinjiang Geol. Bureau and Xinjiang Petrol.
Bureau eds., Paleontological A tlas of West
North China, Xinjiang Uygur Autonomous
Region, no. 2. Geol. Publishing House, Beijing,p. 7-113, pI. 1-30. (in Chinese)
Dutkevich, G.A., 1934: Some new species of
Fusulinidae from the Upper and Middle Carboniferous Verkhne-chussovskye Gorodki on the
Chussovaya River (western slope of the middle
Ural). Trudy Neft. Geol. -Razved. Inst., Ser. A,
vol. 36, p. 1-98, pis. 1-6. (in Russian with English
summary)
Ginkel, A.C. van, 1965: Carboniferous fusulinids
from the Cantabrian Mountains (Spain).
Leidse Geol. Med., Dell 34, p. 1-225, pIs. I-53
Grozdilova, L.P. and Lebedeva, N.S., 1954: Foraminifera of the Lower Carboniferous and Bashkirian strata of the Middle Carboniferous of theKolov-Vishersky Basin. Trudy Vses. Neft.

635

Nauchno-Issled. Geol.-Razved. Inst. (VNIGRI), N. Ser., vol. 18, (Mikrofauna SSSR Sbornik 7), p.4-236, pis. 1-15. (in Russian).
Hasegawa, Y., 1967: Profusulinella daiyamensis n.
sp. from the Profusulinella Zone of the Akiyoshi
Limestone Group. Sci. Rep., Niigata Univ., Ser.
E, no. I, p. 9-15, pis. 1-3.
H uzimoto, H., 1932: Geological study of the southeastern part of the Kanto Mountains. Jour.
Geol. Soc. Japan, vol. 39, no. 466, p. 430-457. (inJapanese)- - , 1936: Stratigraphical and palaeontologicalstudies of the Titibu System of the Kwanto
Mountainland. Part 2, Palaeontology. Sci.
Rep., Tokyo Bunrika Daigaku, Sec. C. vol. I, no.
2, p. 29-125, pis. 1-26.
Igo H., 1957: Fusulinids of Fukuji, southeastern partof the Hida Massif, central Japan. Sci. Rep.,
Tokyo Kyoiku Daigaku, Sec. C, vol. 5, no. 47, p.
153-246, pIs. 1-15.
- - and Adachi, S., 1981: Foraminiferal biostratigraphy of the Ichinotani Formation(Carboniferous-Permian), Hida Massif, central
Japan, Part I, Some foraminifers from the upper
part of the Lower Member of the Ichinotani
Formation. Sci. Rep., Inst. Geosci., Univ. Tsukuba, Sec. B, vol. 2, p. 101-118, pis. 4-6.
- - and Kobayashi, F., 1974: Carboniferous
conodonts from the Itsukaichi district, Tokyo,
Japan. Trans. Proc. Palaeont. Soc. Japan, N.
Ser., no. 96, p. 411-426, pI. 56.
- - and - - , 1980: Carboniferous corals from the
Itsukaichi district, Tokyo, Japan. Sci. Rep.,
Inst. Geosci., Univ. Tsukuba, Sec. B, vol. I, p.
149-162, pis. 13-15.
Ishii, A., 1962: Upper Paleozoic of the Nakatsu-gawa
area, Okuchichibu. Bull. Chichibu Mus. Nat.
Hist., no. II, p. 1-21. (in Japanese with English
summary)
Ishii, K., 1985: Fusulinacean and smaller foraminifer
fossils of Yura Town. In, Ichikawa, K., Ishii,
K., Yamagiwa, N. and Yao, A., Geology of
Yura Town. p.28-39, 3 pIs., Historical Recordsof Yura Town, Educational Broad of Yura
Town. (in Japanese)
Kanmera, K., 1955: Fusulinids from the Yayamadake Limestone of Hikawa valley, Kumamoto
Prefecture, Kyushu, Japan, Part 2, Fusulinids of
the Upper Carboniferous. Japan. Jour. Geol.
Geogr., vol. 27, no. 3-4, p. 177-192, pis. II, 12.
Kobayashi, F., 1988: Late Paleozoic foraminifers of
the Ogawadani Formation, southern Kwanto
Mountains, Japan. Trans. Proc. Palaeont. Soc.
Japan, N.S., no. 150, p. 435-452,7 Figs.
Lee, J.S., 1927: Fusulinidae of North China.
Palaeont. Sinica, vol. 4, no. I, p. 1-173 pis. 1-24.
Lebedeva, N.S., 1954: Lower Carboniferous for-

636

Fumio Kobayashi

aminifers of the Kuznets Basin. Trudy Veses.
Neft. Nauchno-Issled. Geol.-Razved. Inst. (VNIGR/), N. Ser., vol. 18, (Mikrofauna SSSR Sbornik 7), p.237-295, pIs. 1-12. (in Russian)Loeblich, A.R., Jr. and Tappan, H., 1988: Foraminifer genera and their classification. 970 p.,
847 pIs., Van Nostrand Reinhold, New York.
Manukalova-Grebenyuk, M.F., Jlina, M.T. and Serejenikova, T.D., 1969: Atlas of foraminifer ofMiddle Carboniferous in Dnieper-Donets Basin.
Minist. Geol. Nauchno-Issled. Geol.-Razved. Inst.
(Ukrnigri), 288 p. (incld. 69 pIs), Izdatel. Nedra,
Leningrad. (in Russian)Matsusue, K., 1986: Foraminiferal biostratigraphy ofthe lower part of the Akiyoshi Limestone Group.
Sci. Rep., Dept. Geol., Kyushu Univ., vol. 14, no.
4, p. 163-185, pIs. 2-7. (in Japanese with English
abstract)
Morikawa, R., 1955: Schwagerininae in the vicinityof the Shomaru Pass, eastern part of Kanto
Mountainland, central Japan. Sci. Rep.,
Saitama Univ., Ser. B, vol. 2, no. I, p. 45-114,
pIs. 5-15.
Niikawa, J., 1978: Carboniferous and Permian
fusulinids from Fukuji, central Japan. Jour.
Fac. Sci., Hokkaido Univ., Ser.4, vol. 18, no. 4,
p. 533-610, pIs. 1-14.
Ota, M., 1971: Faunas and correlation of the"Uzura" Quarry Limestone of Akiyoshi, Southwest Japan, Part 2, Fusulininan fauna. Bull.
Akiyoshi-dai Sci. Mus., no.7, p.65-74, pIs. 12,
13.
- - , 1975: The Akiyoshi Limestone Group. In,
Kawano, M., Okamura, Y., Mikami, T., Nishimura, Y., and Ota, M., The Carboniferous andPermian of Yamaguchi Prefecture. p.54-69,
pIs. JIE-I-4. In, Geology of Yamaguchi
Prefecture, Yamaguchi Prefect. Mus. (inJapanese)
Ozawa, T., 1975: Stratigraphy of the Paleozoic andMesozoic strata in the Tamagawa area, southernpart of the K wanto Mountains. Sci. Rep., Dept.
Geol., Kyushu Univ., vol. 12, no. 2, p. 57-76, pIs.
7-10. (in Japanese with English abstract)- - and Kobayashi, F., 1986: Stratigraphy and geologic structure of the Paleozoic and Mesozoic
strata in the southern part of the Kwanto Mountains, central Japan. Bull. Hyogo Univ. Teacher
Educ., vol. 6, p. 103-141. (in Japanese withEnglish abstract)- - and - - , 1990: Carboniferous to Permian
Akiyoshi Limestone Group. In, Organizing
Committee Benthos '90 ed., Fossil and Recent
benthic foraminifera in some selected region ofJapan. Guidebook for field trips, 4th Intern.
Symp. on Benthic Foram., Sendai, 1990, p. EI31, pIs. 1-13.

__, __ and Watanabe, K., 1991 : Biostratigraphic
zonation of Late Carboniferous to Early Permian
sequence of the Akiyoshi Limestone Group,Japan and its correlation with reference sectionsin the Tethyan region. Saito Ho-on Kai, Spec.
Pub., no. 3, p. 327 -334, figs. 3-6.
Putrja, T.S., 1940: Foraminifers and stratigraphy
from the Upper Carboniferous sediments in theeastern part of the Donetz Basin. AzowskoChernomorskoye Geologicheskoye Upravl.,
Materialy po geologiy i poleznym iskopayemym,
vol. II, p.I-146, pIs. 1-14. (in Russian withEnglish summary)- - , 1948: Protriticites - a new genus of fusulinids.
Trudy L'vovskogo Geol. Obsche. Gosud. Univ.
im Ivana Franko, Ser. Paleont., no. I, p.89-96,
pI. I. (in Russian)Rauser-Chernousova, D.M., 1938: Upper Paleozoic
foraminifers of the Samara Bend and the TransVolga region. Trudy Geol. Inst., Akad. Nauk
SSSR, vol. 7, p. 69-167, pIs. 1-9 (in Russian)--and Fursenko, A.V., 1959: Principles of
Paleontology, Part I, Protozoa. 482 p., 13 pIs.
Izdatel. Akad. Nauk SSSR, Moskva. (in Russian)- - , Gryzlova, N.D., Kireeva, G.D., Leontovich,
G.E., Safonova, T.P. and Chern ova, E.!., 1951 :Middle Carboniferous fusulinids of the Russian
Platform and adjacent regions. 380 p., 58 pIs.,
Inst. Geol. Nauk, Minist. Neft. Promyshlennosti SSSR, Akad. Nauk SSSR, Moskva. (in Russian)
Reytlinger, E.A., 1961: Stratigraphy of Middle Carboniferous strata of Skv. no. I section of
Krasnaya Polyna in the central Volga area.
Region. Stratig. SSSR, vol. 5, p. 218-260, pIs. 14. (in Russian)Rozovskaya, S.E., 1950: The genus Triticites, its
development and stratigraphic significance.
Trudy Paleont. Inst., Akad. Nauk SSSR, vol.
26, p. 3-78, pIs. 1-10. (in Russian)- - , 1963: Ancient representatives of the fusulinids
and their ancestors. Ibid., vol. 97, p. 1-128, pIs.
1-22. (in Russian)--,1975: Composition, phylogeny and system of
the Order Fusulinida. Ibid., vol. 149, p. 1-208,
pIs. 1-35. (in Russian)
Sada, K., 1972: Fusulinids of the Profusulinella Zoneof the Taishaku Limestone (Studies of the stratigraphy and microfossil faunas of the Carboniferous and Permian Taishaku Limestone in west
Japan, no. 2). Trans. Proc. Palaeont. Soc.
Japan, N. Ser., no. 87, p. 436-445, pIs. 52, 53.
1975: Early and Middle Pennsylvanian
fusulinacea from Akiyoshi. Mem. Fac. Intergr.
Arts and Sci. 4, Hiroshima Univ., vol. I, p. 1-29,
pIs. 1-7.
Sakai, A., 1987: Geology of the Itsukaichi district.

978.

Carboniferous foraminifers from ltsukaichi District

With geological sheet map as I: 50,000, Geol.
Surv. Japan, 75 p. (in Japanese with English
abstract)
Sashida, K., 1981: Primitive fusulinids from the
Shishidedai area, northeastern Akiyoshi Plateau,Southweat Japan. Sci. Rep., Inst. Geosci., Univ.
Tsukuba, Sec. B, vol. 2, p. 1-16, pis. 1-3.
Schell wi en, E., 1908: Monographie der Fusulininen,
Teil II. Die Fusulinien des Russisch-Arktischen
Meeresgebietes. Palaeontgr., vol. 55, p. 145-194,pis. 13-20.
Sheng, J.e., 1958: Fusulinids from the Penchi Seriesof the Taitzeho Valley, Liaoning. Palaeont.
Sinica, N. Ser. B, no. 7, p. 1-119, pis. 1-16. (inChinese and English)
Suyari, K., 1962: Geological and paleontologicalstudies in central and eastern Shikoku, Japan,
Part 2, Paleontology. Jour. Gakugei, Tokushima Univ., (Nat. Sci.), vol. 12, p. 1-64, pis. 112.
Takashima, K. and Koike, T., 1984: Stratigraphy
and geological structure of the Mesozoic strata in
the Gozenyama-Itsukaichi area, southeastern partof the Kanto Mountains. Sci. Rep., Yokohama
Natl. Univ., Sec. II, no. 31, p. 29-49. (in Japanesewith English abstract)
Thompson, M.L., 1948: Studies of American
fusulinids. Univ. Kansas Paleont. Contr., no.4
(Protozoa, art. I), 184 p., 38 pis.
Toriyama, R., 1958: Geology of Akiyoshi, Part 3,
Fusulinids of Akiyoshi. Mem. Fac. Sci., Kyu-

637

shu Univ., Ser. D, vol. 7, p. 1-264, pis. 1-48.
Ueno, K., 1989: Carboniferous and Lower Permian
foraminiferal biostratigraphy in the Akiyoshi
Limestone Group, Studies of the Upper Paleozoic foraminifers in the Akiyoshi LimestoneGroup, Southwest Japan, Part I. Bull.
Akiyoshi-dai Mus. Nat. Hist., no. 24, p. 1-39, pis.
1-8. (in Japanese with English abstract)- - , 1991 : Upper Carboniferous fusulinaceans fromthe Akiyoshi Limestone Group, Southwest
Japan, Trans. Proc. Palaeont. Soc. Japan, N.
Ser., no. 163, p. 807-827, 6 Figs.
Wagner, R.H., Higgins, A.e. and Mayen, S.V. eds.,
1979. The Carboniferous of the USSR. 247 p.,
28 pis. Yorkshire Geol. Soc. Occasional Pub., no.
4.

Watanabe, K., 1974. Profusulinella assemblage in
the Omi Limestone, Niigata Prefecture, central
Japan (Studies of Carboniferous fusulinacean ofOmi, Part I). Trans. Proc. Palaeont. Soc.
Japan, N. Ser., no. 92, p. 371-394, pis. 51-53.
Yamagiwa, N. and Kubota, M., 1980: Late Carboniferous fusulinids from the Tsuruga Limestone,
Fukui Prefecture. Chigaku Kenkyu ( Geosci.
Magazine), vol. 3, nos. 10-12, p.471-474. (inJapanese)
Zeller, D.E., 1953: Endothyroid foraminifera andancestral fusulinids from the type Chesterian(Upper Mississippian). Jour. Paleont., vol. 27,
no. 2, p. 183-199, pis. 26-28.

Akiyoshi t'ca-, Guangxi /Aim, Ichinotani - /~, Itsukaichi .li8m, Kamiyozawa ...t.~~,Kawai }II#, Kitaosogi ~t'J\'i!l'*, Liaoning j!~, Maping f.!;3jZ, Mitake ffElJR";, Mitsuzawa.:::::. ':;~, Mt. Hinode 80)tfjilJ, Mt. Asou ~~ilJ, Musashi ~!il, Musashi-itsukaichi ~!il.li
8m, Nishitama im37}i!J1, Ogawadani 'NII~, Omi Wffl}, Raidenyama fH~ilJ, Shomaru lE
J;L, Taishaku 1iiJI!R, "Taitzeho" (Taizihe) :7;;:.:rtI, Takamizuyama ii1li7.l<ilJ, Torinosu.\i!;/~, Yayamadake ~ilJR";, Yura ESJ5t.

OOJRilJttlHiffl5, Ii.Elm~~O)~Ek;'5:1[J "/ 7ift~.I!.it*21rJLs1t~: ~*ilJ:it!!i¥.iffl5, .li8
m:it!!~O)~.:z. 7*d{11JD{;;fq;:~;th~15ER::'6-0)70 ';J ~ ~;tWJ:Im15.I!.R*d*tp ~~M~Jv.A*dO)
1rfLs1~15~i£:T~. ~gU~ ht.:15.I!.R*dO)~:rL.9:H~15I;t 361/.li, 65 1I1;:&~. ;:h~ 0) oJ i?,
Eostaffella, Profuslinella t.t c", Ify~ I} 7 /r)'MO)~:rL;J:!JaH;t~*ilJ:it!!-\bimi¥.i8*71-1lfL'~;t~jH;: l., iJ'i£: l., t.t It '. Endothyra igoi, Eostaffella kamiyozawensis, Profusulinella hinodensis,
Pseudoendothyra musashiensis 0) 4 fill ~ ~ U 8 1I 0) ~:rL£R 1~15 ~ ~d~ l., t.: •,N,*XxTrans. Proc. Palaeont. Soc. Japan, N.S., No. 176, pp. 638-649,7 Figs., December 30, 1994

979. THE SHELL STRUCTURE OF THE CARAPACE IN
XES TO LEBER IS HANAII ISHIZAKI(CRUSTACEA, OSTRACODA)*MICHIAKI YUMOTO
Department of Environmental Science, Graduate School of Scienceand Technology, Kumamoto University, Kumamoto, 860

Abstract. The development of carapace shell structure during ontogeny of Xestoleberis
hanaii Ishizaki, 1968 was investigated with the aid of a scanning electron microscope (SEM).
Photographs of broken sections of carapaces ranging from the second instar (the adult-7
instar) to adult reveal that the carapace is composed of four distinct layers: I) an organic
fibrous layer that is characterized by a network of organic fibers with few calcite grains; 2)a foliated layer formed by an aggregation of plate-like grains; 3) a granular layer consistingof an aggregation of granular grains; and 4) a prismatic layer constructed of an aggregationof columnar grains extending perpendicularly to the valve surface. Three of the layers, i.e.,
all but the organic fibrous layer, are distinguished by the shape and arrangement of calcite
grains. The calcified procuticle of adult specimens is composed of an outer organic fibrous,
a middle granular, and an inner prismatic layer. That of juvenile specimens in the second
to fourth instars consists of only the foliated layer. That of juvenile specimens in the fifthand sixth instars develops outer granular and inner prismatic layers. The seventh and eighth
instar juveniles possess a procuticle of the same three layers as in the adult. During growth,
the shell structure of this species thus undergoes a change in its constructional design between
molt stages, particularly from fourth instar to fifth instar and from sixth instar to seventh
instar.
Key words.
hanaii.

Ostracoda, shell structure, ostracod carapace, ontogeny, Xestoleberis

bisanensis (Okubo, 1975) corresponds to thearrangement of epidermal cells; thus the surface structure of the carapace is in some sensea reflection of the underlying cellular tissue.
The distribution of normal pore canals on the
carapace may reflect the arrangement of nervous tissue, since the pore canals are a part ofthe sensory organ and the sensory hair connects with the nerve cells (Tsukagoshi, 1989).
The ontogenetic changes of these organs provide useful information for taxonomy andphylogenetic reconstruction. Phylogenetic
relations of specific and generic groups of
ostracods have been estimated based on the
ontogenetic change of the distributional pattern of pore systems (Ikeya and Tsukagoshi,

Introduction

In the past, research on ostracod valves has
extensively been carried out solely on thebasis of their outward morphology. However, anatomical information recorded within
the hard tissue can be decoded, if we know
the relationship between the hard tissue andthe cellular tissue. For example, in work of
extreme importance to those working on
phylogenetic reconstruction, Okada (1981,1982) pointed out that the reticulation patternof the carapace surface of Bicornucythere• Recei ved June I I, 1994; revised
accepted August 17, 1994

man uscri pt

638

979.

Shell structure of Xestoleberis hanaii

1988; Tsukagoshi, 1990; Tsukagoshi and
Ikeya, 1991; Irizuki, 1993).
What shell structure makes ostracod valvessuch excellent "recorders"? The outerlamellar cuticle, often simply called the"ostracod shell," is divided into threedifferent layers: outer epicuticle, middle
procuticle and inner membranous layer.
The epicuticle is not calcified (Bate and East,
1972), and this layer of Bicornucythere
bisanensis is made up of three layers, discriminated by TEM observation (Okada.
1982). The procuticle is composed of small
calcareous grains enclosed by an organic
membrane (J ~rgensen, 1970). SylvesterBradley and Benson (1971) called the procuticle the "foliated layer" because it contains
flattened grains. Langer (1973) was able todistinguish different types of structuralarrangements of the grains in some Ordovician to Recent ostracods. He classified
the grains into three grades; I) U nregelmaBig polyedrische Kristallite, 2) Plattige
Kristallite, 3) Prisma-artige, irregulare groborder diinnsaulige Kristallite. Sohn andKornicker (1988) investigated the shell structure of carapaces in myodocopid ostracods.
and reported five primary components andsome combinations of each of these primary
components. They discussed the taxonomic
distribution of the primary components.
The studies of Langer (1973) and Sohn andKornicker (1988) suggest the procuticle may
not be merely a single type of foliated layer,
but in fact varies. The inner membranous
layer, unknown in detail in its structure, is
non-calcified. In this paper the terms ofthese three layers in the outer lamellar cuticle
are after Okada (1982).
During growth, ostracods molt their carapaces until adulthood. The shell structure
in juveniles has been discussed by Sohn andKornicker (1988). They suggested that thevalves of juveniles of two different sizes havethe same combination of primary components. Up till now, observations of the shellstructure of all instar juveniles have not been639

reported. This paper addresses the questionof whether the shell structure of the carapaceof juveniles in each instar is, in fact, the samestructure as in the adult.
In this paper the shell structure of carapaceof X. hanaii is described with respect to thecalcified procuticle and its ontogenetic variations.

Material and methods

Xestoleberis hanaii Ishizaki, 1968 is common in near-shore habitats of the JapaneseIslands. Its kidney-shaped carapace has asmooth surface without ornamentation (Figure I-I). Sexual dimorphism is distinct, i.e.,
the posterior of the female is more roundish
than the male. The female holds several eggs
and juveniles of the first and second instars in
its posterior body cavity (Figure 1-3). Earlier instars of egg-laying ostracods are hard to
recover. Even if we find earlier instars of
ostracods in sediment samples, it may bedifficult to identify them. It is easy to obtainthe first and second instar juveniles of X.
hanaii, however, because X. hanaii isOVOVIviparous. Therefore, X. hanaii is asuitable species for ontogenetic study. The
first instar of X. hanaii has antennules andantennae, but does not have a carapace; thecarapace is formed at the second instar(Okubo, 1984).
In this study the animals were taken fromtwo locations, near Kameshima Island andHikisakamatsubara Beach on the northeastern side of Amakusa Shimoshima Island,
Ariakekai Bay, western Kyushu, Japan (Figure 2). In the laboratory, live Xestoleberis
hanaii were sorted and fixed in 4% glutaraldehyde solution immediately after collection.
Some females with eggs were picked up before
treatment and cultured in a petri dish. Afterleaving the mother specimens, the second
instar juveniles were used as experimental
material. The animals were killed by formaldehyde solution and washed in distilledwater, and then the soft parts were removed

640

Michiaki YumolO
drying under vacuum for about three hours.
The valves of younger juveniles than the sixth
i nstar were freeze-dried before they were cut,to avoid a loss of very small fractured valve
fragments during preparation .

Shell structure of carapace in
Xestoleberis hanaii

Figure I. XeslOleberis hanaii Ishi zaki , 1968.
Female. 1. Lateral view of left val ve. 2. Internalview of left valve. 3. Internal view with soft part,
eggs, the first a nd the second in stars. Scale bar = 100,urn.

from the carapace.
The valves of the adult and older juveniles
in the seventh and eighth instars were broken
into several pieces with a razor. The fractured surface of each valve fragment was etchedusing 4% EDT A-2N a, then washed in distilled wa ter. Samples were prepared for
SEM photogra phy by freeze drying, submerging in liquid nitrogen for several minutes, andShell structure in adult: The outer lamellar cuticle, not counti ng the margi nal zone ofthe valve, has a thickness of about 171lm in
the adult. The outer lamellar cuticle of X.
hanaii is divided into three layers ; outer
epicuticle, middle procuticle and inner membranous layer (Figure 3) . The epicuticle is I
11m thick . It is divided into a homogenous
outer layer and a n inner layer with a network
structure. The procuticle, under the epicuticle, is the thickest layer in the outer lamellar
cuticle. SEM observations show that theclacified procuticle is composed of threelayers. The organic fibrous layer in the outer
pa rt is seen to be a network of organic matter(OF in Figure 4- 1) . This layer, as stained byhematoxylin-eosin , is distinguished by a dimlayer from the other layers (arrow OF in
Figure 4- 2) . Figure 4- 1 shows organic fibers
connecting to the outer epicuticle, and branching off and binding to each other to form a
network. In specimens treated by EDT A , nograins appea r in the organic fiber network.
The middle layer of the procuticle, the gra nular layer, is composed of an aggregation ofirregularly shaped granules (G in Figure 4- 1).
Each grain is less than 111m in diameter.
The interstices between the grains are filledwith organic matter forming the network ofthin membrane. The organic fibers in thispart are finer than those in the abovementioned organic fibrous layer. The innerpart of the procuticle, the prismatic layer, is
occupied by columnar grains. Each grain isarranged perpendicular to the inner surface ofthe carapace. There are two types of prismatic grains : one is thin and foliated (P in
Figure 4- 1) ; the other has a rod-I i ke shape979.

Shell structure of Xestoleberis hanaii

130°
132°
34° ---+---+---4-~

641

N

*

KameshimaIslandAmakusa
ShimoshimaIsland31 ° ---+--"""'-+--1

1 Ian
Figure 2. Map of northeastern corner of Amakusa Shimoshima Island showing two sampling
locations indicated by star marks. One near Kameshima Island, lat. 32°32.1 'N, long. 130° I 1.9'E, sandy
bottom overgrown with eel grass Zostera. Another at Hikisakamatsubara Beach, lat. 3T32.8'N, long.
130 IO.I'E, bottom containing calcareous algae. Water depth of both locations about 20cm at low-tide.
0

EPICUTICLE --_~----,PROCUT~LE--~<\\MEMBRANOUS
LAYER-----OUTER LAMELLAR
CUTICLE

Figure 3.
terminology.

Diagram of the ostracod valve and(P in Figure 4-3). Quantity of the organic
matter is less in the prismatic layer than in theouter two layers. The procuticle of adultspecimens is made up of three component
layers: organic fibrous, granular and prismatic. The membranous layer is the thinnest
in the outer lamellar cuticle. The membranous layer continues to the wall of pore
canals, but its detailed structure cannot beseen in SEM observation.
In the muscle attachment area (Figure 5-\)the shell structure does not show a combination of three components. The organic membrane extends from the margin of the scar to
the epicuticle (Figure 5-2). Fine fibrous
filaments run in various directions and many
granular and a few prismatic grains occupy
this area.
Newly formed cuticle: Ostracods shed
their carapaces for growth. Growing individual must prepare the next (new) cuticle
under the old cuticle before molting. Most

642

Michiaki Yumoto

Figure 4. Shell structure of ostracod carapace in adult. 1. Edge view at a break in the outerlamellar cuticle. The procuticle can be seen between epicuticle and membranous layer. 2. Light
micrograph of adductor muscle fibers and a pore canal in transverse section of a specimen embedded inparaffin. Three small arrows in cuticle indicate the pan structure. 3. Vertical section at a pore canal.
Scale bars: I = I ,urn; others= 10 ,urn. e: epicuticle, m: membranous layer, mf: adductor muscle fiber,
pc: pore canal, OF: organic fibrous layer, G: granular layer, P: prismatic layer.

979.

Shell structure of Xestoleberis hanaii

crustaceans reabsorb calcium from the old
cuticle before molting. However, Turpenand Angell (I 97 I) found neither resorption of
calcium from the old cuticle nor calcium
storage in the living tissues of the ostracod
Heterocypris. This suggests that ostracods
obtain calcium from the surrounding water
and/or their foods when they need it.
The dorsal part of the left valve of theeighth instar was cut out (Figure 5-4), so thatthe new outer lamellar cuticle of adulthood,full of wrinkles, was exposed. The external
shapes of the new pores had already been
formed on the surface of the new cuticle(Figure 5-3). The fractured surface of the
newly formed cuticle shows granules, about 2,um in diameter, underlying the new epicuticle (Figure 5-6). These granules may be
epidermal cells making the new procuticle.
It is notable that the membranous layer of theold valve is still present in spite of the growthof premolt tissues (arrow m in Figure 5-5).
The membranous layer is dissolved in many
crustaceans before molting, to reabsorb calcium from the old cutile. However, thepresence of the membranous layer before
molting in ostracods supports the statementof Turpen and Angell (1971) that ostracods
do not reabsorb calcium from the old carapace before molting.
Ontogenetic changes of shell structure:
During growth ostracods shed their smaller
old carapaces. Eight clusters of specimen
sizes are recognized in X. hanaii, interpreted
as eight ontogenetic stages. As the first instar juvenile does not have the carapaces(Okubo, 1984), specimens in the smallest
cluster are identified as juveniles in the second instar that have been released from theirmothers. This species molts eight times
before adulthood.
The procuticle of younger juveniles fromthe second to fourth instars consists only ofplate-like crystals arranged parallel to thesurface of the carapace. This structure,
called the foliated layer, is similar to thefoliated layer of Sylvester-Bradley and Benson

643(1971), but much thinner (Figures 6-1, 2,3).
The procuticle of the fifth instar shows
quite different structure than the fourth instar.
Its procuticle is formed of outer granular andinner prismatic layers, not the foliated layer(Figure 6-4). The grains of the outer partare arranged irregularly. Short prismatic
grains are concentrated in the middle andinner parts of the procuticle. Based on thistype of structure, the fifth instar is considered
to have already an adult-type shell construction. The sixth instar juvenile also has the
procuticle being constructed by granular andprismatic layers (Figure 6-5). The rod-likecrystals of the prismatic layer clearly appear
in this stage.
In the procuticle of seventh-instar juveniles
the organic fibrous layer is recognized underthe epicuticle (Figure 6-6), although thefibers do not show full development of theorganic fibrous layer as in adulthood. The
organic fibrous layer first appears in theseventh instar. In the eighth instar the
procuticle is exactly the same as in the adult(Figure 6-7).

Discussion
In the procuticle of X. hanaii, there arethree different grain shapes: foliated, granular and prismatic. J¢rgensen (1970) notedthat the grains in the cuticle are enclosed byan organic membrane. It has been reported
that this organic structure is an organic framework of chitin fibers (Bate and East, 1972,1975), an irregular space lattice structure ofchitinous fibers (Langer, 1973), a piled membranous structure with many spaces between
the undulating membranes (Okada, 1982),
and a net-like counterpart of each "primary
component" (Sohn and Kornicker, 1988).
The shape of the calcareous grains seems to be
similar to the spaces in the organic structure.
These observations may show the shell compositions, which are the organic fibrous, thefoliated, the granular and the prismatic layers
in this paper, in the procuticle to be regulated

644

Michiaki Yumotoby the organic structure, as the shell composition is an aggregation of calcite grains.
The shell structure in the muscle attachment area suggests a close connection between
the shape of calcite grains and the organic
structure (Figure 5-2). The adductor muscle
fibers connect to the central muscle scars.
This central muscle scar area seems to receive
the force when valves are closed. The relations between the outer lamellar cuticle andthe adductor muscle fibers have been discussed in detail by Okada (1983). He revealed
the three-demensional shell structure of the
cuticle of the muscle scars in B. bisanensis.
I n the procuticle, the filamentous network
extends outward to the surface of the cuticle
near the margin of each scar, which he named
the "pan structure". The pan, as Okada
pointed out, made use of the filamentous
network as an anchor in the mass of grains in
the procuticle. In X. hanaii variations in theorganic structure of the procuticle cause local
variations in the shell structure of the muscle
attachment area.
The mechanism of cuticular formation is
known for the carapace of decapods. The
carapace contains four discrete layers: theepicuticle, the exocuticle, the endocuticle andthe membranous layer. The exo- and endocuticles are secreted by the organic matrix
before and after molting. Both cuticles arecalcified after molting. Although both the
exocuticle and endocuticle have many lamellae, the two cuticles differ in their lamellar
spacing, with the interlamellar distance being
less in the exocuticle than in the endocuticle(Roer and Dillaman, 1984).
In ostracods, a new carapace is formed
before and after molting. The epicuticle andouter part of the procuticle are secreted before
molting. After the old carapace is cast off,
ostracods make a strong and thick carapace ina short time. According to Turpen andAngell (1971), the calcification of the carapace in the ostracod Heterocypris occurs
within seven hours after molting. In X.
hanaii the new carapace hardened within 24
hours after molting (Okubo, 1984). The
inner part of the procuticle must be secreted
and calcified immediately after molting for
rapid shell formation. The primary functionof the prismatic layer may be for the quick
and efficient secretion and calcification of the
procuticle.
There are three steps in the ontogenetic
development of the shell structure of the
procuticle: the first step, with only a foliatedlayer from the second to fourth instars; thesecond step, with granular and prismatic
layers in the fifth and sixth instars; and thelast step, with organic fibrous, granular andprismatic layers from the seventh instar to
adult. The shell structure thus undergoes adiscontinuous change in its constructional
design from the fourth to the fifth instars.
The change of the shell structure from thesixth to seventh instars is gradual, adding theorganic fibrous layer. As the organic structure controls the layers, it seems that thisspecies changes the mechanism of formationof the organic structure when it reaches thefifth instar and seventh instar.
Figure 7 shows the relationship between
the thickness of the outer lamellar cuticle andinstar number. The younger instars possess avery thin cuticle. Although the rate ofincrease in the thickness is rapid between theeighth instar and the adult, it is constant and~Figure 5. Shell structure of muscle attachment area and newly formed cuticle. 1. Inner surface ofcentral muscle scars of left valve. 2. Shell structure in vertical section of muscle attachment area. 3.
Wrinkly new outer lamellar cuticle and two sieve type pores (s) on its surface. 4. The anterior dorsal viewof 8th instar juvenile in which the dorsal part of left valve was removed. Wrinkly new outer lamellar cuticle
was already formed before next molting. 5. Old and new outer lamellar cuticles. The membranous layerof old cuticle (arrow m) and surface of the new outer lamellar cuticle (arrow n). 6. Vertical section of new
procuticle. Granules show epidermal cells. Scale bars: I and 4= 100 pm; 3= I pm; others= 10 pm. g:
granules, m: mambranous layer, n: new outer lamellar cuticle, 0: old outer lamellar cuticle.

979.

Shell structure of Xestoleberis hanaii

645

Michiaki Yumoto

646

Table 1. Morphological features of ostracods occurring in different molt
stages (modified from Kesling, 1961, Q20).

Appendages

Taxon
ci.
CIl
~

a)
()
~

~

a)

~

I-<
a)

.~
J",

c:u
...t:;)
c:u

a)
~

.....

"0

.5

..... "0

....
~

(,,)

c:u
~

"0
oJ::!
·c
S"':I ·c....
0.. I:::
0.. ..r::>.
>. >.
u u >< U
(,,)

a)

a)

,.Q

1

1

1

2

2

2

e:::I 3

Z

S

CIl

c::

4
5
6

3
4
5
6

3
4
5
6

7
8

7
8

7
8
Adult

1
1 2
2 3
3 4
4 5
5 6

~

c::
c:: c::
B B
c::
:::I

a -<

I-<
a)

- -..... .....eJ)

ci.
CIl

x
x
x
x
x
x
x
x
x

-a)

,.Q
.....
"0 ~

~

eJ)
a)

eJ)
a)

.....

()

()

I-<

~
I-<
0

I-<

()

~

~

0

.....
"5
.....
c::
~

CIl

0
~
-5 -5 ~
-5!a ~ ....CIl "0c:: 'E 0c:: a) ~:::I~ ~ ~ ...-.I ~ ("f') 0 0 u.

x
x
x
x
x
x
x
x
x

~

x
x
x
x
x
x
x
x
x

A

x
x
x
x
x
x
x

A

a

a
A
A
A

x
x A a
x
x x A ax x x A a x
x x x x A x
x x x x x x

x, structure present indefinitive form; A, anlage always present; a, anlage
present in some species, but not in others; .. , no trace of structure found.

relatively slow during earlier juvenile development.
In earlier instars the molting interval isshort and the juveniles have a thin cuticle.
According to Okubo (1984), the intervals
between molting were three or four days foryounger juveniles and four or five days forolder juveniles. It may be wasteful, if theyounger juveniles were to construct the sameprocuticle as in the adult for the short interval
between moltings. Therefore, it may be energetically advantageous for younger juveniles
to form a simpler carapace than that formedby older juveniles and adults.
Table 1 modified from Kesli ng (1961) summarizes the appearance of appendages in
ontogeny. Juveniles of X estoleberis sp.
younger than the fifth instar have neither
thoracic legs nor furca. In the fifth instar the

first thoracic leg and furca appear, and otherlegs emerge in later stages. At the molt stage
when the procuticle structure changes the first
thoracic leg and furca first appear. This
correspondence suggests that the fifth instar isa turning point for the growth of both soft
parts and hard tissue.
It is shown that the shell structure of
Bivalvia may be a conservative feature andtherefore may be an effective characteristic forrecognizing phylogenetic relationships(Shimamoto, 1986). Although the shellstructure of the ostracod carapace isanatomically very different, it may also be thecase that phylogenetic relationships inostracods can be enshrined in the types ofprocuticle structure and layers.

~
Figure 6. Shell structure of ostracod carapace in each instar. 1. 2nd instar. 2. 3rd instar. 3. 4th
instar. 4. 5th instar. 5. 6th instar. 6. 7th instar. 7. 8th instar. All scale bars= I Jim. F: foliatedlayer, G: granular layer, OF: organic fibrous layer, P: prismatic layer.

979.

2

Shell structure of Xestoleberis hanaii

647

Figure 7. Thickness of outer lamellar cuticle in each instar among 66 specimens meusured.
represent individual specimens; circles show mean values.

Acknowledgments
Deep appreciation is expressed to Professor
Yasuhide Iwasaki of the Department of Earth
Sciences, Faculty of Science, Kumamoto
University for useful suggestions and discussion concerning various aspects of this study.
I would like to thank Professor Noriyuki
Ikeya and Dr. Robert M. Ross of the Instituteof Geosciences, Faculty of Science, Shizuoka
University for encouragement throughout thecourse of the present study and for reading
and commenting on a draft of the manuscript.
References cited
Bate, R.H. and East, B.A., 1972, The structure of the
ostracode carapace. Lethaia, vol. 5, p. 177-194.
- - and - - , 1975, The ultrastructure of the
ostracode (Crustacea) integument. In, F.M.
Swain, L.S. Kornicker and R.F. Lundin eds.,
Biology and paleobiology of Ostracoda. Bull.
Amer. Paleontol., vol. 65, p. 529-547, pis. 1-4.
Ikeya, N. and Tsukagoshi, A., 1988, The interspecificrelations between three close species of the genus
Cythere O.F. MUller, 1785. In, T. Hanai, N.
Ikeya and K. Ishizaki eds., Evolutionary Biologyof Ostracoda - its Fundamentals and Applications, p. 891-917. Kodansha, Tokyo and EI-

Squaressevier, Amsterdam.
Irizuki, T., 1993, Morphology and taxonomy of someJapanese hemicytherin Ostracoda - with particular reference to ontogenetic change of marginal
pores -. Trans. Proc. Palaeont. Soc. Japan,
N.S., no. 170, p. 186-211.
Ishizaki, K., 1968, Ostracodes from Uranouchi Bay,
Kochi Prefecture, Japan. Tohoku Univ., Sci.
Rep., 2nd ser. (Geol.), vol. 40, no. 1, p. 1-45, pis.
1-9.
J¢rgensen, N .0., 1970, Ultrastructure of someostracods. Bull. Geol. Soc. Denmark, vol. 20, p.
79-92.
Kesling, R.Y., 1961, Ontogeny of Ostracoda. In,
R.C. Moore ed., Treatise on invertebrate Paleontology. Part Q- Arthropoda 3 - Crustacea-Ostracoda, p. QI9-Q20. Univ. Kansas Pressand Geol. Soc. America, Lawrence, Kansas.
Langer, W., 1973, Zur Ultrastruktur, Mikromorphologie und Taphonomie des OstracodaCarapax. Palaeontographica, Abt. A, Bd. 144,
Lfg. 1-3, Seite I-54, Tafeln 1-15.
Okada, Y., 1981, Development of cell arrangement inostracod carapace. Paleobiology, vol. 7, p.276280.
- - , 1982, Structure and cuticle formation of thereticulated carapace of the ostracode Bicornucythere bisanensis. Lethaia, vol. 15, p.85101.
- - , 1983, Muscle scars and structure of the muscle
attachment in the carapace of the ostracodeBicornucythere bisanensis. Micropaleontology,

979.

Shell structure of Xestoleberis hanaii

voL 29, p. 66-77, pis. 1-4.
Okubo, L, 1984, On the life history and the size of
Xestoleberis hanaii. Res. Bull. Shujitsu Coll.,
no. 14, p. 19-43.
Roer, R. and Dillaman, R., 1984, The structure andcalcification of the crustacean cuticle. A mer.
Zool., voL 24, p. 893-909.
Shimamoto, M., 1986, Shell microstructure of the
Veneridae (Bivalvia) and its phylogenetic implications. Tohoku Un iv. , Sci. Rep., 2nd ser.
(Ceol.), voL 56, no. I, p. 1-39, pis. 1-20.
Sohn, I.G. and Kornicker, L.S., 1988, Ultrastructureof myodocopid shells (Ostracoda). In, T.
Hanai, N. Ikeya and K.Ishizaki eds., Evolutionary Biology of Ostracoda ~ its Fundamentals
and Applications, p.243-258. Kodansha,
Tokyo and Elsevier, Amsterdam.
Sylvester-Bradley, P.c. and Benson, R.H., 1971, Terminology for surface features in ornate

649

ostracodes. Lethaia, voL 4, p.249-286.
Turpen, J.B. and Angell, R.W., 1971, Aspects ofmolting and calcification in the ostracod Heterocypris. BioI. Bull., voL 140, p. 331-338.
Tsukagoshi, A., 1989, The character of male
copulatory organ and the distributional patternof normal pore canals in the ostracode genus
Cythere ~ consideration of their usefulness forthe phylogenetic reconstruction~. Benthos
Research, nos. 35/36, p. 89-96. (in Japanesewith English abstract)- - , 1990, Ontogenetic change of distributional patterns of pore systems in Cythere species and its
phylogenetic significance. Lethaia, voL 23, p.
225-241.
- - and Ikeya, N., 1991, A redescription of Cythere
japonica Hanai, 1959 (Podocopida: Ostracoda).
Zoo!. Jour. Linn. Soc., voL 103, p. 129-143.

Amakusa Shimoshima Island ~1j["f~, Ariakekai Bay 1'fEJJ3$, Hikisakamatsubara iJ l:I;&t~
JJi(, Kameshima Island .~.

Xestoleberis hanaii Ishizaki (Ej3~~. 1t1f~S) O)~~fIj~: B*O)if}J¥~f;::1:,~."9 ~1t~

SO) I fl Xestoleberis hanaii Ishizaki, 1968 f;:: -::H' -r, mtO)~WTjHj ~:it1t11~JlJiL"ll'l~ lA-:.
P.JGj:;$:.to J:: lf~1:O)mtO)JJi( ~ 1- ~ '7 Ii, 4 -:JO)m~-1'f~1t~*fH~~' ~:tkm~· m:tkm~·
tt:tkm~-~J::~-rmP.JG~h~. 1'f~1t~.m~~~<3-:JO)m~~, ~.EmO)~n~
J:: IJ IR5JUL" ~ ~. RlG1*O)JJi( ~ 1- ~ '7IHf·j]!UtJ' 61'f~1t~., m:tk, tt:tkm~O)IIIIH;::l!C>,U"9~~,~1:L"~2.~64.0)JJi(~1-~'7~~:tkm~~~~6~~.5.t6.0)JJi(~1-~'7 -r·li, jf.j]!IH;::m:tkm~:b~, ~j]!IH;::tt:tkm~:b!9EJl"9 ~. 7 • .to J:: If 8 .0)JJi( ~ 1- ~ '7 L"li,P.JGj:;$: t fI'IJ cm~O)l!C>,u t ~ ~. *flO)mi:m~li, 4 .:b' 6 5 .f;::~&:"9 ~ t ~ t 6 .:b' 6 7.f;::~&:"9 ~ t ~ 1;::JJi(~ 1-~ '7O)mP.JG~~1r.~1t~;: t :b~~~ ht-:.

~*JI[EJJ3

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 176, pp. 650-660, 10 Figs., December 30, 1994

980.

AN INQUIRY INTO THE MECHANICS OF
TRIGONIID HINGE SYSTEM*YOSHIO YUKI
NHK; Japan Broadcasting Corporation
Jinnan, Shibuya-ku, Tokyo, ISO

Abstract. The gear-like intricate dentition of the Trigoniidae appears to fix the axis ofvalve opening and closing movement, while the opening and closing forces must be generated
independently by the ligament and adductor muscles. As a result of experiments andmoment analysis on living specimens of Neotrigonia margaritacea (Lamarck), it was foundthat the three axes determined by dentition, ligament and adductor muscles are largely
different from one another in orientation. Provided that minimum friction is required forthe smooth hinge movement, the opening force by ligament and closing force by adductor
muscles have to compensate each other, and the axis of their resultant force may coincidewith the dentition axis. The relatively short ligament in trigoniids seems to enable such aremote valve movement axis from the postero-dorsal margin as well as the formation ofremarkably pennate shells like Pterotrigonia.
Key words. Trigoniidae, Neotrigonia margaritacea, dentition axis, ligament axis,
closing moment axis.

direction of its rotation axis. This axis does
not seem to coincide with the direction of theligament (or the postero-dorsal margin ofshell), though the actual valve rotation ofliving bivalves must be controlled by the totalof ligament force and adductor force(Trueman, 1969). The valve opening andclosing movement of bivalves, in general, isdirectly related with such essential behaviors
for life as respiration, feeding, reproduction,
locomotion and protection.
The aim of this study is to evaluate themechanics of the valve opening and closing
movement by estimating the axes, which are
independently inferred from the analyses ofligament force and resultant adductor force.
Because the actual valve rotation axis can be
strictly determined by the dentition,
trigoniids are regarded as convenient material
for this analytical study.

Introduction
The adaptive morphology of trigoniids has
attracted the attention of many paleontologists and malacologists because thisgroup exhibits various peculiar morphological features. In particular, the dentition of trigoniids is very unique and stable,
and the walls of hinge teeth and sockets areinvariably carved by a number of curvilinear
striae, termed secondary dentition (Stanley,
1977, 1978).
As pointed out by Makiyama (1926), thestriae must represent the traces of the opening
and closing movement of the valves.
Because the striated teeth and sockets act as
intricate gears, it is difficult for us to open an
articulated specimen of Neotrigonia margaritacea (Lamarck) without recognizing the* Recei ved A pri I 8, 1994; revised man uscri pt accepted
October 17, 1994
650

980.

Mechanics of trigoniid hinge system

Materials

Living materials.-Living shells of
Neotrigonia margaritacea (Lamarck) wereused for the observation and analysis ofmorphology. They were obtained on May
24, 199 I, from sandy mud substrata at 6-10 m
depth in Western Port Bay, Victoria, Australia. Some shells of infaunal bivalvespreserved in the University Museum, University of Tokyo, were also used for the present
comparative study.
Fossil materials.- The following specimens were used: Nipponitrigonia kikuchiana(Y okoyama) from the Lower Cretaceous
Miyako Group in northeast Honshu; Pterotrigonia eufaulensis (Gabb) from the Upper
Cretaceous Ripley Formation in Tennessee,
U.S.A.; Yaadia ainuana (Yabe and Nagao)
from the Upper Cretaceous Middle Yezo
Group in central Hokkaido; silicone replicaof a specimen of Trigonioides tetoriensis
Maeda from the Lower Cretaceous Tetori
Group in central Honshu.

Procedures and results
Procedure 1.

Valve rotation axis

The hinge teeth of post-Triassic trigoniids
are surprisingly stable in spite of the great
variability in the shell outline and surface
sculpture (Cox, 1952; Cox et al., 1969),
though a polyphyletic origin of this family
has been suggested by some authors (Newelland Boyd, 1975). The anterior and posterior
walls of two strong teeth of the right valve
and those of corresponding sockets of the left
valve have about a dozen of the characteristic
curvilinear striae. As Makiyama (1926)
pointed out, these striae seem to be concentric
circles if observed perpendicularly to thewall. He mentioned further that they represent the traces of loci on the tooth and socket
surface in the process of valve rotation (Figure I).
Makiyama's insight is here developed to amethod to estimate the unique rotation axis

651

from the dental structure. Because the wallsof every tooth and socket are planar, the striae
must look nearly straight and parallel to one
another when they are observed from thedirection perpendicular to the exact rotation
aXIS.

The measuring device introduced here is toquantify the straightness of the striae (Figure2). The striated teeth of a right valve ofNeotrigonia margaritacea (Lamarck) was
viewed from the ventral side and enlarged
twenty times with the aid of a profile projector (Nikon V -160). Then, both ends ofeach curved stria were linked by a straight
line, and the area enclosed by the curved andstraight lines was measured by counting thenumber of dots on the display of a personal
computer. Of course, the less total areameans the closer approach to the direction
perpendicular to the rotation axis.
As shown in Figure 3, the total of the areas
enclosed by curved and straight lines becomesminimum when the hinge teeth is viewed
from the direction of 57 degrees with thepostero-dorsal margin of shell. This meansthat the -actual valve rotation axis in N.
margaritacea is 33 degrees away from thepostero-dorsal margin.
The same method can be applied to fossil
trigoniids and trigonioidids if the hinge teeth
are well exposed. Suitable specimens may berare, but I could examine some specimens of
Nippon itrigon ia kikuchiana (Yokoyama),
Pterotrigonia eufaulensis (Gabb), Yaadia
aimtana (Yabe and Nagao) and Trigonioides
tetoriensis Maeda and determine the approximate direction of their rotation axes (Figure
4).
Procedure 2.

Relative length of ligament

The ligament of trigoniids and many
heterodont bivalves (e.g. lucinids, cardiids
and venerids) is opisthodetic and external.
Cox et al. (1969: N81) mentioned, "Whenthere is a ligamental nymph, its upper surface
will usually indicate the direction of the[hinge] axis." This may be true as to many
heterodont bivalves with long external liga-

Yoshio Yuki

652

(A)
LV

DENTITION AXIS

-8

H....,------)--.-RV

(B)

(~

Figure 1. Geometrical model for valve rotation movement. A: When the valves rotate around ahinge ax is, eac h locu s on the teeth sc ribes a circle bound in a plane perpendicu lar to the axis. B: Ventral
view of a right valve of Neotrigonia margaritacea (Lamarck) ( x 2), in which the striae o n the tooth wa ll s
look straight and para ll el. C: Postero-ventral view of the sa me spec imen , in which the striae look curved .
Arrows indicate the direction of views.

ment. In trigo nii ds, however, the axis ofvalve rotation and prolongation of the ligament (or postero-dorsa l margin of she ll ) are
obvio usly discordant , as were ascertained byProcedure I . Intuitively, the degree of the
discordance is related to the relati ve length ofthe li gament. The ligament length of so me

trigoniid s a nd heterodont bivalves were measured and standardized in accordance withthe radius of an equivalent circ le, the area of
whi ch is equal to the shell surface in latera lvIew.
The relative length of the ligament is about
31% of the radius of equivalent circle in N.

980.

Mechanics of trigoniid hinge system

(e)

653

(number of dots)

40000
VI

z

0

~~\\~ t~~~1

f=

«

30000

a:
I-

VI

u.
0

«
w
a:

«

20000

10000

0

(B)

20

1J'

30

40
ANGLE

-8

50

60

(deg.)DENTITION AXIS)I))) )))) J(A)Figure 3. Results of the procedure I (see also
Figure 2). The "straightness" of the striae becomes
optimal, when the hinge is viewed from the directionof about 5T away from the postero-dorsal margin.
This means that the dentition axis intersects themargin at an angle of about 33°.

margaritacea and about 25% in Pterotrigonia
eufaulensis (Figure 5). These values arenotably smaller than other heterodont
bivalves (except for the Cardiidae).
Procedure 3.

Figure 2. Measuring the "straightness" of thestriae on the tooth walls. A: Measuring device
contrived with a silicone replica of a right valve ofNeotrigonia margaritacea (Lamarck). B: The
striae are projected and enlarged on the screen of a
profile projector. C: Traces of the striae are bridged, and the total of enclosed areas is measured by
the number of dots on the screen of a personal
computer.

Valve opening axis by ligament force

The main function of ligament is to open
the valves when the adductor muscles relax,
and it also serves to unite the dorsal margin of
the valves (Trueman in Cox et aI., 1969).
The axis of valve opening force can be
examined by measuring the gape between thetwo valves when the force is applied perpendicularly to the commissure plane (Figure 6).
In order to eva Iuate the effect caused only by
the ligament, all the hinge teeth and soft part

Yoshio Yuki

654

(A)

(a) Neotrigonia margaritacea-·;'·(~:;:r:;:~ ".: . ... .... ..

(b) Nipponitrigonia kikuchiana•
1 em

a:=:::>(c) Pterotrigonia eufaulensis='(e) Trigonioides tetoriensis(d) Yaadia ainuana(B)

Figure 4. A: Dentiti o n axes of so me trigoniid a nd tri go ni o idid bi va lves: Neotrigonia margaritacea(Lamarck), Nipponitrigonia kikllchiana (Yokoyama), Pterotrigon ia elljalilensis (Gabb), Yaadia ainllana(Yabe a nd Nagao) , Trigonioides teloriensis Maed a. B: Ventra l view o f the hin ge of Pterotrigonia
elljalilensis , sho w ing nearl y strai ght stri ae o n the too th wa ll s.

980.

Mechanics of trigoniid hinge system

L655

of a living specimen of N. margaritacea were
eliminated. The ligament was kept wet withsea water during the experiment. First, acompressive force was operated perpendicularly to the commissure plane at a certain
point F on the ventral margin. The fixed
point U at the umbo (proximal end of ligament) was linked with the point F, and theperpendicular line to FU through the point U
is termed a "temporary ligament axis." Theangle between this axis and the extension of
the postero-dorsal shell margin was measured.
Then, the points A and P were set at the

STDed LIGAMENT LENGTH:R
TEMPORARY
LIGAMENT AXIS

100T--------------------------~(0/0)---r--_--=-~U- -

G-

80
J:

t-

O
Z

w 60

..J

p

tZ

w

==
ct 40
0

:J
~

GI

C

20

li;
o

T

Figure 5. Comparison of relative ligament
length, which is standardized by the radius of anequivalent circle. Trigoniids reveal shorter ligament
than most heterodont bivalves.

Figure 6. Estimating method of the valve opening axis by ligament, using a living specimen of N.
margaritacea, the teeth and soft part of which arecompletely eliminated. A perpendicular compressive force is applied at an optional point (F), and the"temporary ligament axis" is drawn to set two points(A and Pl. U is a fixed point throughout the valve
rotation. The gapes are measured at A and P, when
the gape at F becomes 4.0 mm.

Yoshio Yuki

656

anterior and posterior margins of the shellwith distances of 20 mm from the temporary
ligament axis. When the gape between thevalves at the point F became 4 mm, the gapes
at the points A and P were measured. This
experiment was repeatedly performed by shifting the point F along the ventral margin.
When the gapes at the points A and P wereidentical, the temporary ligament axis was
regarded as representing the real valve opening axis by the ligament force alone.
The valve opening force by ligament in N.
margaritacea holds an axis at about 48
degrees away from the postero-dorsal marginof shell (Figure 7). Although this experiment can be performed only in living bivalves
with active ligament, it should be emphasizedthat this axis does not agree with the pro lon7

E'
g

5

"

4

W

3

o

ij
SA X AA' = SP X PP'

...J
...J

:r:

RA X SA = RP X SP

AO : PO : SP : SA

POST. GAPE

W

0(

u

--<>-- ANT. GAPE
-

6

Q"

(A)

U)

2
1
10

20

30

40

ANGLE

--CJ

50

60

70

(deg.)DENTITION
AXIS

Figure 7. Results of serial experiments in theprocedure 3 (see also Figure 6). The shell gapes at
A and P become equal when the "temporary ligamentaxis" intersects the postero-dorsal margin at an angleof about 48°.

----------- DENTITIONAXISCLOSING MOMENT
AXISFigure 8. Estimating method of the closing
moment axis. A: The valve closing axis is determined by the balance of two moments by the anterior
and posterior adductor muscles. SA, SP: Areas ofanterior and posterior adductor muscle scars in perpendicular views to the commissure. RA, RP:
Distances between the valve closing axis and thecenter of each muscle scar (A, P). B: Geometrical
diagram to determine the closing moment axis on the
prolongation line AP, and the point 0 is set where
the reversed areal ratio SP/SA equals AO/PO.
Then, AA' : PP' equals SP : SA, because of the similarity between LIOAN and LIOPP', and the two
moments become equal. C: Closing moment axisof N. margaritacea, intersecting the postero-dorsal
shell margin at an angle of about 20°.

980.

Mechanics of trigoniid hinge system

gation of ligament on the postero-dorsal
marglll.
Procedure 4. Valve closing moment axis by adductor muscles

A moment on a rotation axis is generally
calculated by the product of the strength of aforce by the distance between the operating
point and the rotation axis. The relative
contractile forces of the two adductor muscles
in a given specimen may be most reasonably
estimated by measuring the areas of themuscle scars. Stanley (1972) noted a similar
procedure to evaluate two contractile forcesof pedal retractors. The expected val ve closing axis by the resultant force of adductor
muscles has to lie in the direction where themoments of the two muscles are equal to eachother (Figure 8A). This axis can be determined by introducing a simple geometry (Figure 8B).
The closing moment axis of N. margaritacea intersects the postero-dorsal margin ofshell at an angle of about 20 degrees (Figure
8C).

Discussions
By the procedure I -4, the orientations of
three different axes were estimated independently by the analysis of curvilinear striae on
the walls of teeth, the experiment of ligament
force and the moment calculation of thecontraction of adductor muscles. They are
here called the dentition axis, ligament axis
and closing moment axis, respectively.
It is notable, at least in the Trigoniidae,
that the dentition axis is coincident neitherwith the prolongation of ligament nor withthe postero-dorsal magin of the shell, though
the valve opening force must be generated
only by the ligament. If the prolongation ofligament (or postero-dorsal margin) werecoincident with the rotation axis, the animal
could not open the valves in such a pennate
form as Pterotrigonia and Apiotrigonia. On
the other hand, no physical problem occurs if
the actual axis of rotation is apart from the657

postero-dorsal margin. This condition is
actually ascertained in Pterotrigonia
eufaulensis (Gabb) (Figure 9). As evidenced by the procedure 2, Neotrigonia margaritacea (Lamarck) (and probably all the otherpost-Triassic trigoniids) has decidedly shorter ligament in comparison with many heterodont bivalves with parivincular ligament(Figure 5). Only some species of the Cardiidae share relatively short ligament with the
Trigoniidae.
Most bivalves have more or less prosogyrous umbones which are coiled forward (Stanley, 1975, 1978). The prosogyrous or orthogyrous shell commonly results in a nearlystraight postero-dorsal margin, and this condition is compatible with a relatively long
ligament. The opisthogyrous shell coiling of
Pterotrigonia (and some other genera of the
Trigoniidae) would produce a pronouncedly
concave postero-dorsal shell margin andwould not allow a long ligament.
Generally, in many heterodont bivalves

DENTITION AXIS--8-DIRECTION OF
LIGAMENT GROOVE
Figure 9. Dentition axis and the prolongationof ligament groove in a pennate trigoniid Pterotrigonia eufaulensis (Gabb). If the ligament groove
were coincident with the valve rotation axis, valve
opening would be impossible because of the collisionof the posterior ends of the two valves.

Yoshio Yuki

658

(B) CLOSING MOMENT(A) LIGAMENT

MA<MP
MA=MP

F'-- F

ANT.

POST.

ANT.

\\

(C)

POST.

II

COMPENSATION~ (J

CLOSING MOMENT AXISDENTITION AXIS
LIGAMENT AXIS

Figure 10. Relation between the dentition axis and the balance of forces by the ligament andadductor muscles. The ligament axis (A) and the closing moment axis (B) are largely discordant inorientation, but the two forces seem to compensate each other to form a "balanced axis (C)". The"balanced axis" has to coincide with the dentition axis, because minimum dental friction is required forthe smooth movement of valves. MA, MP: Moments of anterior and posterior adductor muscles.

980.

Mechanics of trigoniid hinge system'without such intricate teeth as trigoniid dentition, two independedt forces by ligament andadductor muscles may operate in order toopen and close the valves in opposite directions. The relative movement of the twovalves is determined by the balance of these
two forces (Trueman in Cox et at., 1969). In
view of the analysis of ligament in N. margaritacea, it is noticeable that the ligament axis
is further apart from the postero-dorsal shell
margin than the dentition axis which is theactual rotation axis of the valves (Figure 7).
On the contrary, the closing moment axis in
N. margaritacea is close to the postero-dorsal
margin than the actual valve rotation axis
(Figure 8C).
The opening and closing forces of thevalves may have their own axes but seem tocompensate each other to form a "balanced
axis." When the operating point F shifts toF' so that the "temporary axis" approaches
the dentition axis, the posterior gape between
the two valves becomes wider than the anterior gape (Figure lOA). On the contrary, if
the closing moment axis were coincident withthe dentition axis, the posterior closing
moment would become larger than the anterior, and the anterior gape would become
wider than the posterior gape (Figure lOB).
Because the actual valve rotation is determined by the interaction of the forces ofligament and adductor muscles, the "balanced
axis" must lie between the ligament axis andthe closing moment axis. Although its quantitative dynamic analysis is difficult at present,
this condition seems to be realized in themorphology of N. margaritacea. Provided
that minimum dental friction is required forthe smooth movement of the valves, it isreasonable to consider that the "balanced
axis" coincides with the dentition axis (Figure IOC).

659

on the walls of teeth and sockets; the striae
must look nearly straight and parallel, if they
are observed from the direction perpendicular
to the axis.
The postero-dorsal margin of a bivalve
does not necessarily correspond to the valve
rotation axis. Particularly in the
Trigoniidae, the rotation axis is far apartfrom the postero-dorsal margin. Such aremote axis enables a highly pennate shellform like Pterotrigonia. The relatively shortligament of Neotrigonia margaritacea(Lamarck) (and probably all the other speciesof the Trigoniidae) is compatible with therotation axis much apart from the prolongation of ligament.
The valve rotation movement in N. margaritacea must be determined by the interaction of two independent forces generated by
the ligament and adductor muscles. The
present analysis proved that the axes of thetwo forces are largely different from eachother in orientation. The gear-like intricate
dentition of trigoniids indicates that theactual valve movement axis is almost strictly
fixed, and -that the "balanced axis" of the twoforces substantially coincides with the dentition axis.
Acknowledgements
I am especially grateful to Professors I.
Hayami and K. Tanabe for their kind guidance during the course of this study andcritical reading of the manuscript. Special
thanks are due to Dr. K. Bandel and S.Isaji
who provided fossil specimens. Dr. T. Darragh and Mr. J. Austin kindly supported myfield work in Australia. Thanks areextended to Drs. K. Abe, T.Oji and Y.
Shigeta and Mr. T. Ubukata, who provided
me with helpful suggestions in the laboratory
works.

Conclusion
The valve rotation axis of trigoniids can be
uniquely determined by the curvilinear striae

References
Cox, L.R.,

J 952:

Notes on the Trigoniidae, with

Yoshio Yuki

660

outlines of a classification of the family. Proc.
Malacol. Soc. London, vol. 29, p.45-70.
- - et al., 1969: Treatise on Invertebrate
Paleontology. Part N, Mollusca 6, Bivalvia (2vols.). 952 p. Geol. Soc. America and Univ.
Kansas.
Makiyama, 1., 1926: Notes on Neotrigonia and thehistory of the Trigoniidae. JOllr. Geol. Soc.
Japan, vol. 33, p.389-394.
Newell, N.D. and Boyd, D.W., 1975: Parallel evolution in early Trigoniacean bivalves. Bull. Amer.
Mus. Nat. Hist., vol. 154, p. 55-162.
Stanley, S.M., 1972: Functional morphology andevolution of byssally attached bivalve mollusks.

Jour. Paleont., vol. 46, p. 165-212.
- - , 1975: Why clams have the shape they have: anexperimental analysis of burrowing.
Paleobiology, vol. [, p.48-58.
- - , [977: Coadaptation in the Trigoniidae, aremarkable family of burrowing bivalves.
Palaeontology, vol. 20, p.869-899.
- - , [978: Aspect of the adaptive morphology andevolution of the Trigoniidae. Phil. Trans. Roy.
Soc. London, Ser. B, vol. 284, p.247-258.
Trueman, E.R., [969: Ligament. In, Cox, L.R. etal., Treatise on Invertebrate Paleontology. Part
N, Mollusca 6, Bivalvia, vol. [, p. N58-64. Geol.
Soc. America and Univ. Kansas.

~ I) ~.::. 7~4(7)~=I=..,t :t.J.::..A.L..~:-:>\' \"(C7)~~: =t:lcJ'l.O)mMOOMf;l:!W1iH: M~J$;b~J!Ill..,,;b> l.." r I) :f.::. 7f40)=t:lcJ'l.0)¥.f-Y/<ji*lt;dlJ!illllH;I:, ~ -:::> I;(l;i.

.lH::1:.l;i.t±:l't'11-rt:k:i.o.

<l.." -r ~>.o J: -:5 f;::5i!.;;t.o. m,1:. Neotrigonia margaritacea-rO)~MU: -'f:-;( /' riW1JTO)*6;!;lU:: l.." -r, :ljz0) 3 -:::>O)~: llIliO)m~;b>Gt:k:i.o~; !W1iH;::
J:.oOO <110)${,'~; M~$O)Mc:.o11O)${,'~, O)-ftVfhO)~O):1Jr<Df;l:*~ <J!<t:t'?
-r ~ >.0 ;: i:::;b{ b ;b> '? to:. • m G;b> t;d~* 0) jf] ~ 0) to:. o\b f;::, !W1iH;:: J: .0 00 <11 i::: M~$ 0) M c:
.0 11;b~ -:5 i </~'7 /' A ~ i::: t) OOM~jf] H:h>, -f 0)*6* i::: l.." -rt:k: i .0 ~ f;l:llIliO)m~;b> Gt:k:i .o~ i::: J: <-3& l.." -r~,.o. ito:., r I) :::t.::. 7f40).lt~i¥J~~'!W*f;l:~0)1&'FN~;b> G/Iilh
to:. OOM~ ~ 'ilJ'iffgf;:: l..", Pterotrigonia 1;::5i!. Gh.o J: -:5 t:t!f;fJ!<t:t l.." ~ tJ C:~0)~0)7r%~ tJ'ilJ'iffg
I;:: l.." -r~'.o ;: i::: ;b{~~~ h.o.

-g-'? -r~O)OOM~jf]O)@]~~ ~~JE

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 176, pp. 661-676, 7 Figs., December 30, 1994

981.

DIVERSITY OF CHLAMYS (BIVALVIA) FROM THE
PLIOCENE OGIKUBO FORMATION,
CENTRAL JAPAN*
KAZUT AKA AMANO
Department of Geoscience, Joetsu University of Education,
Joetsu, Niigata Prefecture, 943

Abstract. Many specimens of Chlamys were obtained from the Early Pliocene
Ogikubo Formation in northern Nagano Prefecture, central Honshu. These are identified
with the following six species: Chlamys (Chlamys) cosibensis (Yokoyama), C (C) ingeniosa tanakai Akiyama, C (C) foeda (Yokoyama), C (C) insolita (Yokoyama), C("C ") lioica shigaramiensis Amano et Karasawa and C (Leochlamys) tanassevitschi(Khomenko). The last species has hitherto also been known as Chlamys daishakaensis
Masuda et Sawada or C iwakiana (Yokoyama).
The diversity of this chlamid fauna is attributed to the distributional pattern andgeologic ranges of the species. Chlamys lioica shigaramiensis and C tanassevitschi are
confined to the northwest flank of the Orihashi Syncline, which was deeper and colder than
the southeast flank area where C foeda occurred.
Chlamys ingeniosa tanakai, C insolita and C lioica shigaramiensis are Miocene relict
forms. They survived in the studied area to the Middle Pliocene, owing to the cold-water
embayment conditions. The mixture of Miocene and Pliocene type species accounts for thediversity of Chlamys from the Ogikubo Formation.
Key words.

Diversity, Chlamys, Pliocene, Ogikubo Formation.

bivalves in the Japanese Neogene as well asfrom this formation (Masuda, 1962a), and aresuitable for examining the Mio-Pliocene
faunal change in Japan because of their fast
rate of evolution (Stanley, 1986). The genus
Chlamys is abundant in the Ogikubo Formation and was studied by some previous
authors (Yokoyama, 1925b; Akiyama, 1958;
Masuda, 1962a; Amano and Karasawa,
1986; Amano et al., 1991). When he summarized the taxonomy of Japanese Neogene
pectinids, Masuda (1962a) described the following species from the "Shigarami Formation" including the Ogikubo: Chlamys
cosibensis cosibensis (Yokoyama), C. c. turpicula (Yokoyama), C. daishakaensis
Masuda et Sawada, C. insolita (Yokoyama)
and C. tanakai Akiyama. Later, Amano

Introduction

In Nagano Prefecture, central Japan, many
mollucan fossils occur in the Pliocene Ogikubo Formation (Amano and Karasawa,1993). The fauna is very important for
examining the Mio-Pliocene succession ofshallow sea molluscan fauna in the Japanese
Neogene because the Ogikubo Formation
may be the only embayment setting of Japan
Sea borderland in the Early Pliocene. Moreover, it has been known as a mixed fauna
including typical Miocene and Pliocene
species (Amano and Karasawa, 1993).
Pectinids including Chlamys are common*Received April 7, 1994; accepted September 16,
1994
661

662

Kazutaka Amanoand Karasawa (1986) proposed a new subspecies, shigaramiensis of C. lioica (Dall).
Amano et al. (1991) described C. foeda(Yokoyama) and discussed its ecology andevolution. However, "c. daishakaensis"
from this formation has never been illustrated
or described. Little is known about theexact distribution of the above species in theformation.
It is noteworthy that few deposits in Japan
yield a high diversity of Chlamys in the
Neogene. However, there is no discussion in
the literature on the causes of the high diversity of Chlamys in the Ogikubo Formation.
Therefore, the purpose of this paper is totaxonomically reexamine some species ofChlamys and to discuss the reasons why somany species of Chlamys could live in thestudied area.

Geological and paleoecological settings
The Ogikubo Formation crops out to thewest of Nagano City in the northern part ofNagano Prefecture (Figure I). It has been
folded by the Orihashi Syncline and shows
finer-grained facies on the northwest flankthan in the southeast. On the northwest
flank, the formation mainly consists of siltstone and mudstone associated with sandstone. On the southeast flank, it is chiefly
composed of fine-grained sandstone with siltstone and conglomerate. The Ogikubo Formation unconformably covers the Arakurayama Formation. The upper part of the
Ogikubo is an isochronous deposit to thelower part of the Sarumaru Formation(Amano and Karasawa, 1993). Amano andKarasawa (op. cit.) also assigned an age of 34 Ma to the Ogikubo based on the planktonic
foraminifers and Kj Ar dating.
Amano and Karasawa (1993) recognized
four associations in the Ogikubo molluscan
fauna: Mya-Macoma, MizuhopectenChlamys, Conchocele, and Chlamys-Tridonta
associations (Figure I). Among these, MyaMacoma association is restricted to the inter-tidal zone on the southeast flank. The last
two associations, which occurred at lower
sublittoral and upper bathyal depths, are on
the northwest flank. The upper sublittoral
Mizuhopecten-Chlamys association occurredon both flanks of the Orihashi Syncline.
From the above-noted lithofacies change
and the distribution of molluscan associations, it is obvious that part of the formationon the northwest flank was deposited indeeper water than that on the southeast one.

Localities of Chlamys
Many molluscan fossils were obtained from
25 localities of the Ogikubo Formation(Amano and Karasawa, 1993; Figure 2).
From 16 of these localities, the following fivespecies of Chlamys were collected: Chlamys(Chlamys) cosibensis (Yokoyama), C. (C.)
foeda (Yokoyama), C. (C.) ingeniosa tanakai Akiyama, C. (" Chlamys") lioica shigaramiensis Amano et Karasawa and C. (Leochlamys) tanassevitschi (Khomenko). U nfortunately, Chlamys in solita (Yokoyama)
could not be obtained, but I had an opportunity to examine the holotype (monotype) of
the species.
The total number of localities and specimens herein treated are listed below: C. ingeniosa tanakai, 15 localities (Loc. nos. 2, 4,
6,7,8,10,15,16,17,18,19,21,22,24,25), 130
specimens; C. cosibensis, 6 localities (Loc.
nos. 5,6, 17,21,22,24), 12 specimens; C.
lioica shigaramiensis, 2 localities (Loc. nos.
21,22), 5 specimens; C. foeda, 1 locality(Loc. no. 10),2 specimens; C. tanassevitschi,
I locality (Loc. no. 22), 2 specimens.
Almost all the specimens occurred as single
valves and mainly from fine- to mediumgrained sandstone (Loc. nos. 2, 4, 5, 6, 7, 8, 10,
17, 18) and tuffaceous muddy fine- tomedi um-grai ned sandstone (Loc. nos. 15, 16,
19, 22, 24, 25). At Loc. 21, three species ofChlamys occur in a granule-bearing finegrained sandstone.

981.

Chlamys from Ogikubo Formation

663

J~\.rL!. · ·.

...• pped.rea:! ..........

Nagano.....

\~AGANO PRE,-~

.1

.!

t

/

..

360~~M_._trl·_u_m_o~to~~138 0•.............--

7./"

Q

\

\ ........ .

..J/

If'
\/
, :,
.' I

:'

:

\

'

50km

\.

~ .: ",:..,\.

LEGEND.J'ya-J'acollJa association\..,....\.

....

AJ'izulJopecten-CIJJallJYs ass .
..... ) ...........
:

'.

./'
.,

+ConclJoceJe ass.
....

.CIJJallJys-J'ridonta ass,....

( '\.:Formation boundaryI,...... _.... 0.'.:'-",............... , ......

R.

,i ~. ,"j......

........./
-.~.

o

\v
........,........
.,,'............. ....... :1'~.' ............/.:.'..
.f........ \,)
: :
U

.

\....)=====::::::il~................

...~.

....,......... . ....\...... ,J.......

...,&:......... .

",/ . /...•,: ....-'

,:.,

1::'

:

./

...../ ........

;~·•..•.. .-I.·······/

Figure 1.

Distribution of molluscan associations in the Ogikubo Formation.

Kazutaka Amano

664

Figure 2. Localities of fossils (after Amano and Karasawa, 1993; using the topographical maps of"Togakushi" and "Shinano-Nakajo" scale I : 25,000 published by Geographical Survey Institute of Japan).

Systematic notes on somespecies of Chlamys

Chlamys cosibensis, C. foeda and C. lioica
shigaramiensis were taxonomically examined

in detail by Masuda (1973), Amano andKarasawa (1986), and Amano et af. (1991).
Therefore, in this section, the following three
species will be examined; Chfamys ingeniosa
tanakai, C. insolita and C. tanassevitschi.

981.

Chlamys from Ogikubo Formation

Family Pectinidae Rafinesque, 18 I 5
Subfamily Chlamydinae Korobkov, 1960
Genus Chlamys [Roding, 1798J
Subgenus Chlamys [ROding, 1798J

Chlamys (Chlamys) ingeniosa tanakai
Akiyama, 1958
Figures 3-1, 3, 9

Chlamys sp., Kuroda, 1931, p. 37-38, pI. 2, fig. 9, pI.
3, fig. 10; Tomizawa, 1958, p. 326, pI. 3, figs. 4a,b.
Chlamys ingeniosa tanakai Akiyama, 1958, p. 243245, pI. 36, figs. I, 2a, b, 3a, b.
Chlamys obesa Akiyama, 1958, p.245-246, pI. 36,
figs.4a, b,5a, b,6a, b.
Chlamys (Chlamys) tanakai Akiyama. Masuda,
1962a, p. 186, pI. 22, figs. 4-7; Amano and Karasawa, 1986, pI. 4, figs. 2, 8.

Type locality.-Kawashita (Kawashimo ?),Togakushi-mura, Kamiminochi-gun, Nagano
Prefecture. TKO, Reg. no. 5334.
Remarks.-Chlamys ingeniosa tanakai isof moderate size and the valves are moderately inflated. There are 24 to 28 dichotomous
granulated radial ribs with interstitial ribletson the right valves and 23 to 27 granulated
radial ribs with one or two interstitial ribletson the left valves.
The present subspecies was proposed by
Akiyama (1958) based on specimens from the
Ogikubo Formation. At that time, he also
proposed another species, Chlamys obesa
from a locality near the type locality of thepresent subspecies. Thereafter, Masuda(1962) considered the latter as a synonym of
the former.
Before the proposal by Akiyama, Kuroda(1931) described and illustrated the present
subspecies as Chlamys sp. from Shimosoyama(Ogikubo Formation). However, the figured
specimens are internal casts; none of theshell remains. Its rubber mold (Figure 3-3)
shows the same characteristics as the present
subspecies.
Comparison.- Chlamys ingeniosa tanakai
is slightly different from C. i. ingeniosa (Y 0koyama) from the Miocene Nanao Forma-

665

tion, Ishikawa Prefecture (Figure 3-8,
holotype; Figure 3-5, topotype) by having asmaller apical angle, later splitting radial ribs,
stronger intercalated riblets, and a smaller
resilial pit on the right valve. Chlamys ingeniosa ingeniosa flourished in early Middle
Miocene age and may be an ancestor of C. i.
tanakai.
As already pointed out by Akiyama (1958),
the present subspecies is related to the Recent
Chlamys islandica group. Among them,
Chlamys hindsi (Carpenter) is the most allied
to the present one. However, the left valve ofhindsi has tricarinate radial ribs which havenever been observed in this sUbspecies.
Distribution.-Pliocene Arakurayama andOgikubo Formations.

Chlamys (Chlamys) insolita(Yokoyama, 1925)
Figures 3-2, 7

Pecten insolitus Yokoyama, 1925b, p. 18, pI. 5, fig. 3.
Chlamys (Chlamys) insolita (Yokoyama). Masuda,
1962a, p. 171.

Chlamys anapleus (Woodring). Gladenkov et al.,1984, p. 187, pI. 35, figs. 2, 6 (non pI. 34, fig. 8, pI.
37, figs. 1,3).

Type locality.-Shigarami, Togakushimura, Kami-minochi-gun, Nagano Prefecture.
CM22634.
Remarks and comparison.-Chlamys insolita was proposed on the basis of one rightvalve from Shigarami (Ogikubo Formation)
by Yokoyama (1925b). The present species
is characterized by 21 broad radial ribs withinterstitial riblets and a narrow byssal fasciole.
When they described molluscan fossils
from the Miocene Kakert Suite in western
Kamchatka, Gladenkov et al. (1984) illustrated some specimens as Chlamys anapleus.
As the result of examination of their specimens stored at the Geological Institute of theRussian Academy of Sciences in Moscow, it
has become clear that they differ from Woodring's species by having more numerous

Kazutaka Amano

666

radial ribs. The specimen collected by Dr.
Sinelnikova from the Etolon Suite (Figure 37) also shows the same characteristics as thepresent species.
Chlamys anapleus (Woodring) and C.
strategus (Dall) are allied to this species, butanapleus has 11 radial ribs and strategus has
about 7 ribs.
Distribution.-Miocene Kakert and Etolon
Suites in Kamchatka; Pliocene Ogikubo
Formation in Honshu.
Subgenus Leochlamys MacNeil, 1967

Chlamys (Leochlamys) tanassevitschi(Khomenko, 1934)
Figures 4-1,2,4,5,6,7,5-1,2,3,4Pecten tanassevitschi Khomenko, 1934, p.33-34, pI.
3, figs. 4, 5, pI. 4, figs. 1-5, pI. 5, figs. 3, 4, pI. 6,
figs. I, 2, pI. 7, fig. I
Pecten (Pecten) iwakianus Yokoyama. Nomura andHatai, 1935, p. 102-103, pI. 12, fig. 3, pI. 13, fig. 8.
Pecten (Chlamys) tanassevitschi Khomenko. Slodkewitsch, 1938, p. 108, pI. 20, fig. 5, pI. 21, figs. 13, pI. 22, fig. l.
Chlamys (Chlamys) iwakiana (Yokoyama). Kanehara, 1942, p. 137-138, pI. 15, fig. 6, pI. 16, fig. 5 ;Omori, 1977, p. 68, fig. 5.
Chlamys hastata iwakiana (Yokoyama). Kubota,
1950, p. 14, figs. 52, 64.
Chlamys iwakiana (Yokoyama). Itoigawa, 1958, pI.
I, fig. 12.
Chlamys daishakaensis Masuda and Sawada, 1961, p.
23-25, pI. 4, figs. 8,9; Ogasawara et al., 1986, pI.
52, figs. 18, 19; Akamatsu and Suzuki, 1990, pI.
I, fig. 8; Akamatsu and Suzuki, 1992, pI. 3, fig. 9.
Chlamys (Chlamys) farreri nipponensis Kuroda.
Krishtofovich, 1964, p. 139-141, pI. 19, figs. 2, 3,
pI. 24, fig. 3 (non pI. 17, fig. I); Zhidkova et al.,1968, p. 84, pI. 24, figs. I, 2.
Chlamys (Chlamys) sawanensis Omori, 1977, p.68,
pI. 2, figs. 7a, b.

Chlamys (Chlamys) daishakaensis Masuda and
Sawada. Uozumi et al., 1986, pI. 20, fig. 10.

Type locality.-Exposure along the coast to
the south of Piltuk River, western part ofSchmidt Peninsula, Sakhalin. Lectotype no.
30/5043.
Original description.- "Shell thick, inequilateral, inequivalve; both valves moderately inflated in same extent. Anterior auricle nearly twice as long as posterior one;byssal notch deep, ctenolium considerably
variable. Upper half of anterior auricle ofright valve ornamented with five roughgrooves between imbricated and rounded
ribs, becoming more wide toward upper;
surface of lower half of auricle sculptured bydeep growth lines. Anterior auricle of left
valve with 12 deeply rounded and imbricatedribs, these ribs nearly equal or finer ribs intercalated with stronger ones in places; growthlines also distinct. Posterior auricle of both
valves less massive, and their sculpture considerably fine: except for many narrowly
arranged growth lines, four fine weakly imbricated radial ribs separated by equal interspaces, with two fine radial threads. Number of ribs 22, nearly equal or different fromeach other to some extent. Ribs high androunded with many fine imbrications; interspaces deep, usually broader than ribs, butsometimes equal, very rarely narrower thanribs. Besides concentric sculpture due togrowth, interspaces of ribs with fine andweakly imbricated secondary riblets; numberof secondary riblets attaining three in large
sample; secondary riblets situated on bothsides or one side of main ribs in some cases,
separated from main ribs in another cases;~
Figure 3. 1,3,9: Chlamys (Chlamys) ingeniosa tanakai (Akiyama). I; Loc.7, JUE no. 15429.
3; rubber mold (Kuroda, 1931, pI. 2, fig. 9, JC6(0038), JUE no. 15430. 9; Loc. 10, JUE no. 1543!. 2,7:
Chlamys (Chlamys) insolita (Yokoyama). 2; holotype (CM22634). 7; Etolon Suite, West Kamchatka,
deposited in Geological Institute, Moscow. 4: Chlamys ("Chlamys") lioica shigaramiensis Amano etKarasawa. Loc.22, JUE no. 15432. 5,8: Chlamys (Chlamys) ingeniosa ingeniosa (Yokoyama). 5:
topotype collected by Dr. N. Matsuura. 8; holotype (CM25519). 6: Chlamys ("Chlamys") lioica lioica(Dall). Loc. Bolishoi Cape, Etolon Suite, deposited in Geological Institute, Moscow (N670j82). All
figures are natural in size.

981.

Chlamys from Ogikubo Formation

667

668

Kazutaka Amana

981.

Chlamys from Ogikubo Formation

669

Figure 5. Type specimens of Chlamys (Leochlamys) lanassevilschi (Khomenko) and "Chlamys
daishakaensis Masuda et Sawada" . 1,2: syntypes of Chlamys (Leochlamys) lanassevilschi (Khomenko) , x O.75 , Nos. 24, 30/5043, (reproduced from Khomenko, 1934, pI. 4, fig. 2, pI. 7, fig. l). 3: to po typeof "Chlamys daishakaensis Masuda et Sawada", x O.5, IGPS no. l54l0. 4: holotype of "Chlamys
daishakaensis Masuda et Sawada", X 0.55, IGPS no. 90708.

wide range of variation usually recognized on
secondary ribs. (Originally in Russian , translated into English)".

Remarks .- Chlamys tanassevitschi (Syntypes, Figures 5- 1, 2) is characterized by its
large shell size (maximum length 112 mm,+- Figure 4. 1,2,4,5,6,7: Chlamys (Leochlamys) lanassevitschi (Khomenko). l; X 0.75, Loc. 2 km
upstream bank of Soibetsu River, Hokkaido, Setana Formation, JUE no. l5433. 2, 6, 7; 2, xl, 6, 7 X 0.8 ;Loc.22, JUE nos. l5434~l5436. 4,5; x l, Loc. Kaidate, Niigata Pref., Sawane Formation, JUE nos.
l5437 - l~l5437 - 2. 3: Chlamys (Chlamys) cosibensis (Yokoyama). x l, Loc. 6, JUE no. l5438.

Kazutaka Amana

670

~

.....

.....'..... ' ...

.J•

r\

LEGEND• Cniays ingeniosa tanaKai• C. cosilIensis
foeda... C. tanasseYitscni
iioica snigaraliensis

t.

J

,

I

!

...•..,

1:l.

.......

..••....
.............. ,.

:-....... .•......
~;............

••••• \.

'... ..'.... "-'!.".........

,0-

1km

==:::=3==::::1'

: :

tf

• y .... ..... .

,0.......,I

,~

... /

(

..........~..

(,.
.............:.

,.' ......
.......

, .........'

Figure 6.

....,.........

l'o/

....

t:_

/

......."\....... ...l:.,. . ·~./r···......

y.....

",.'.1:,.0"'".".. .....
/'./

Distribution of Chlamys in the Ogikubo Formation.

981.

Chlamys Jrom Ogikubo Formation. according to Khomenko, 1934), narrowly
elongated anterior auricle of right valve ornamented with four radial ribs, and 22 to 24
imbricated radial ribs on its shell surface witha few intercalated radial threads.
The Ogikubo specimens are large in size
(maximum length 126.9 mm) and have similar
auricular characters. Although they haveless numerous radial ribs (about 20), theseribs are scaled with fine radial threads on
both flanks and three radial threads in eachinterspace. Therefore, the Ogikubo specimens are clearly identifiable with the present
species.
Krishtofovich (1964) and Zhidkova et al.
(1968) misjudged the present species as asynonym of the Recent species Chlamys
Jarreri nipponensis Kuroda. However, it iseasy to distinguish tanassevitschi from the
Recent species by the larger shell, narrowly
elongate anterior auricle of right valve andless numerous ribs on the auricles of both
valves.
When Masuda and Sawada (1961)
proposed Chlamys daishakaensis (Holotype,Figure 5-4), based on specimens from the
Early Pleistocene Daishaka Formation, they
did not compare it with the present species.
As the result of examination of the type specimens, some to po type specimens and somespecimens from the Setana Formation in
Hokkaido (Figure 4-1), I can consider
Chlamys daishakaensis to be a synonym of
C. tanassevitschi because of its large shellsize, similar shell shape and nearly equal
number of ribs.
Many previous authors frequently
identified the present species with Chlamys
iwakiana established by Yokoyama (1925a).
As already pointed by Masuda and Sawada(1961), Chlamys iwakiana differs from C.
tanassevitschi by having a less inflated left
valve and less elevated radial ribs.
According to Omori (1977), his new
species, Chlamys sawanensis slightly differs
from" C. iwakiana" (= c. tanasseivitschi) byhaving fewer secondary radial threads.

671

However, his two specimens are smaller (maximum length, 66 mm) than the present species.
Moreover, some specimens from the Sawane
Formation (Figures 4-5,5) show the samecharacteristics as the present one in shell
sculpture and other features.
Comparison.- The present species is allied
to Chlamys (Leochlamys) tugidakensis
MacNeil (1967) from the Pliocene? of the
Tugidak Island in its narrowly elongate shapeof auricle, and in similar form and number ofradial ribs to the present species. The development of secondary riblets is the most obvious difference between Chlamys tanassevitschi and C. tugidakensis. Interstitial riblets
are rarely present on the right young valves oftugidakensis.
The Recent species, Chlamys (Leochlamys)
Jarreri (Jones et Preston) is another allied
species to the present one. As pointed out
above, the Jarreri has a broader anterior earof right valve, more numerous radial ribs on
the anterior auricle (about six to seven on
right valve, about twenty on the left), andlower radial ribs on the shell surface of both
valves.
Distribution.-Pliocene Pomyr Suite innorthern Sakhalin, Early Pleistocene
Shimonopporo, Setana and Tomikawa Formations in Hokkaido, Plio-Pleistocene Daishaka, Sasaoka, Haizume, Sawane, and Ogikubo Formations in Honshu.
Diversity of Chlamys and its causes
The following chlamids are recorded fromthe Ogikubo Formation; Chlamys ingeniosa
tanakai, C. cosibensis, C. Joeda, c. insolita,
C. lioica shigaramiensis and C. tanassevitschi. In addition to these Chlamys species,
the Ogikubo also yields Swiftopecten swiftii(Bernardi), Mizuhopecten yamasakii (Yokoyama) and Yabepecten tokunagai (Yokoyama) (Amano and Karasawa, 1988).
Other than the Setana, Na-arai and Ogikubo
Formations, there are no Plio-Pleistocene
formations in Japan which yield more thanKazutaka Amano

672-OlalYS- Clzlamys foedaooPacific Ocean""CnIIllTS lioica lioica (Iiocene)-c. I. l. (Pliocene)o C. l. sniKafllliensis

Figure 7.

Geographical distribution of Chlamys foeda, C. tanassevitsehi and C. !ioea group.

981.
Table 1.

Chlamys from Ogikubo Formation

673

Epifaunal bivalves other than pectinids from the Ogikubo Formation

Species namedepth (m)'bottom·'Area boueardi Josseaume
Porterius dalli (Smith)
Mytilus (Crenomytilus) grayanus (Dunker)
Modiolus difficilis Kuroda et Habe
Solamen speetabilis (A. Adams)
Aeesta goliath (Sowerby)
Anomia ehinensis Philippi
Monia maerosehisma (Deshayes)
Neopyenodonte musashiana (Yokoyama)
Crassostrea gigas (Thunberg)

0-20
0
0-20
0-20
30-300100-1,390
0-20
0-40
20-500
0

R
R
R
R
fS
sM
R, fgS
R
M,R
M,R•.•• chiefly after Habe (1977): •• R, Rock; fS, fine sand; fgS, fine pebble-bearing
sand; sM, sandy mud; M, mud.

six chlamids (Masuda, 1962b; this study).
Some taxonomical problems of Chlamys
from the Setana Formation are pointed out
by Shikama and Ikeya (1964) and Uozumi
and Akamatsu (1975). Thus the Ogikubo
Formation represents one of very few PlioPleistocene deposits yielding a diverse
pectinid fauna.
Other than the Chlamys islandica group,
many Recent Chlamys live in the warm
waters around Japan (Higo and Goto, 1993).
Despite its boreal-type fauna (Tomizawa,
1958; Amano and Karasawa, 1993), the Ogikubo Formation yields a high diversity ofchlamids. The high diversity of chlamids
can not be attributed to the climate. Alternatively, the isolation of habitat between eachspecies and some Miocene relict species may
make the diversity of chlamids of the Ogikubo Formation high.
The above six species are not always collected together, but instead occur separately
in the studied area (Figure 6). Two common
species, Chlamys ingeniosa tanakai and C.
cosibensis occur on both flanks of the Orihashi Syncline and are found in both upper andlower sublittoral associations (MizuhopectenChlamys and Chlamys- Tridonta associations).
The occurrence of Chlamys foeda isconfined to the southeast flank while C. lioica
shigaramiensis and C. tanassevitschi occur inthe northwest. C. foeda might have preferred shallower water than the latter two. Judging from the distribution of the above species(Figure 7), the northern limit of the latter two
species is located further north than that of
foeda, and therefore they probably lived incolder water. This estimation is supportedby the following species association. The
latter two chlamids are frequently accompanied by Tridonta alaskensis (Dall) andYabepecten tokunagai (Yokoyama) which
originated in northern Pacific waters and had
migrated southward by the Pliocene (Ogasawara, 1986; Masuda, 1986).
Of the six chlamids, Chlamys cosibensis, C.
tanassevitschi, and C. foeda are commonly
recognized in the Pliocene and Early Pleistocene Omma-Manganji fauna (Otuka,1939). Especially, Chlamys foeda and C.
tanassevitschi have never been found in any
Miocene faunas, but are characteristic elements of the Omma-Manganji fauna(Masuda, 1980).
The Ogikubo Formation also yields thefollowing three species which are confined to
the Pliocene strata around the studied area.
Chlamys ingeniosa tanakai most abundantly
occurs from the formation and is derived from

674

Kazutaka Amano

the Miocene ancestor, C. ingeniosa ingeniosa.
C. lioica shigaramiensis is also derived from
Miocene C. lioica lioica in Kamchatka.
Chlamys insolita has been commonly foundfrom the Miocene Kakert and Etolon Suites
in Kamchatka (Gladenkov et al., 1984) while
the Pliocene occurrence is confined to the
Ogikubo Formation. Therefore, these
species are relicts of the Miocene faunas in
Honshu and Kamchatka. Another reason
for the high diversity of chlamids are attributed to these three Miocene relicts in addition
to Omma-Manganjian species.
As above noted, the Miocene relicts might
have lived on the sublittoral sandy bottom.
There is a problem remaining unsolved about
the reason why some Miocene relict species ofChlamys survived in these habitats which arevulnerable for epifaunal species.
Other than Swiftopecten sWiftii, the eightpectinid species from the Ogikubo Formation
are all extinct. By contrast, all epifaunal
bivalves in this formation other thanpectinids are extant forms (Table I). Other
than Acesta goliath, which lives in the lower
sublittoral to upper bathyal zones where
predators are rare, almost all the species are
now living on hard bottoms of the intertidal
and upper sublittoral zones.
Stanley (1986) suggested the extraordinaryhigh rate of extinction of pectinaceans resultsfrom the heavier predation pressure on thesubtidal soft bottom than on the intertidal
hard bottom where many other epifauna
lived.
In discussing the characteristics of theextinct bivalve genera of the Plio-Pleistocene
Omma-Manganji fauna, Amano and Tanaka(1992) pointed out that the monospecificgenera inhabiting sublittoral sandy bottoms
suffered extinction while those inhabiting therocky shores and the deep water survived.
Conclusively, the sublittoral sandy bottom isa vulnerable place for infaunal bivalves aswell as for epifauna including Chlamys.
One possible cause why the Miocene relicts
survived under such vulnerable conditions is

the cold embayment in the studied area.
Vermeij (1986) pointed out that cold water
can act as an ecological refuge. A representative Pliocene index fossil, Fortipecten takahashii (Yokoyama) occurred in the coldwater embayments, where it was a recliner.
Its mode of life is rare among late Cenozoic
bivalves but was common among Mesozoic
epifaunas (Hayami and Hosoda, 1988). Like
Fortipecten takahashii, the relict Miocene
chlamids could not survive too long andbecame extinct by Middle Pliocene time.
Acknowledgements
I am grateful to Prof. Geerat J. Vermeij of
University of California, Davis, Emeritus
Prof. Koichiro Masuda of the Miyagi University of Education, Dr. Thomas R. Waller of
the Smithonian Institution, Dr. Louie Marincovich, Jr. of the U.S. Geological Survey, andProfessor Kenshiro Ogasawara of the University of Tsukuba for their critical reading of
the manuscript. Prof. Hiroshi Noda andEmeritus Prof. Saburo Kanno of the University of Tsukuba provided useful advices on
the geological and taxonomical problems. I
thank Prof. Itaru Hayami of Kanagawa University, Dr. Valentina N. Sinelnikova of theGeological Institute, Russian Academy of
Sciences, Dr. Nobuomi Matsuura of the
Shiramine-mura Dinosaur Museum, Mr.
Shigeru Karasawa of Yashiro Junior HighSchool and Emeritus Prof. Kunio Tanaka of
Shinshu University for their help to examinesome fossil specimens.
References cited
Akamatsu, M. and Suzuki, A., 1990: Pleistocene
molluscan faunas in central and southwestern
Hokkaido. Jour. Fac. Sci., Hokkaido Univ.,
Ser. IV, vol. 22, no. 4, p. 529-552.
- - and - - , 1992: Stratigraphy and paleoenvironment of the Lower Pleistocene on the hills
around the Ishikari Lowland, Hokkaido. Ann.
Rep., Hist. Mus. Hokkaido, no. 20, p. 1-30. (inJapanese with English abstract).

981.

Chlamys from Ogikubo Formation

Akiyama, M., 1958: New fossil Chlamys from theenvirons of Nagano City, Japan. Trans. Proc.
Palaeont. Soc. Japan, N.S., no.31, p.243-247,
pI. 36.
Amano, K. and Karasawa, S., 1986: A new subspecies of Chlamys lioica (Dall) from the
Pliocene Shigarami Formation developed in theenvirons of Nagano City, Central Japan.
Monogr. Mizunami Fossil Mus., no. 6, p.41-47,
pI. 4.
- - and - - , 1988: Yabepecten and Pseudamiantis from the Shigarami Formation in
Nagano Prefecture, Central Japan. Saito Ho-on
Kai, Spec. Pub., no. 2, p. 507-517, pIs. 1,2.
- - and - - , 1993: Molluscan fauna andpaleoenvironment of the Pliocene Ogikubo Formation in the northern part of Nagano Prefecture, central Japan. Jour. Geogr., vol. 102, no.
5, p.572-582. (in Japanese with English

abstract).
- - and Tanaka, K., 1992: An Omma-Manganjian
bivalvia, Profulvia kurodai (Sawada), from the
Plio-Pleistocene strata of Japan. Bull. Joetsu
Univ. Educ., vol. 12, no. I, p. 115-123, pI. 1.
- - , - - and Karasawa, S., 1991: Chlamys(Chlamys) foeda (Yokoyama) from the Shigarami Formation in Nagano Prefecture, Central
Japan. Ibid., vol. 10, no. 2, p. 305-312, pI. 1.
Gladenkov, Yu. B., Gladikova, V.M., Kafanov, A.N.,
Konova, L.V., Krishtofovich, L.V., Sinelnikova,
V.N. and Popov, S.V., 1984: Marine mollusks.
In, Menner, V.V. ed., Atlas of fauna and floraof the Neogene sediments of the Far East,
Tochilni reference section of western Kamchatka. Trans. Geol. Inst., vol. 385, p. 152-249, pIs.
27-65. (in Russian).
Habe, T, 1977: Systematics of Mollusca in Japan:
Bivalvia and Scaphopoda. 223 p., 74 pIs. Hokuryukan, Tokyo. (in Japanese).
Hayami, I. and Hosoda, I., 1988: Fortipecten takahashii, a reclining pectinid from the Pliocene ofNorth Japan. Palaeontology, vol. 31, pt. 2, p.
419-444.
Higo, S. and Goto, Y., 1993: A systematic list ofmolluscan shells from the Japanese Islands andthe adjacent area. 693 p. Eru-Kairui Shuppankyoku, Yao. (in Japanese).
Itoigawa, J., 1958: Molluscan fossils from Niitsu,
Higashiyama and Takezawa oil-fields, Niigata
Prefecture, Japan. Mem. CoIL Sci., Univ. Kyoto,
Ser. B, vol. 24, no. 4, p. 249-263, pIs. 1.
Kanehara, K., 1942: Some molluscan remains fromthe Setana Series of Hokkaido and from the Taga
Series of the Joban coal-field of Iwaki. Japan.
Jour. Geol. Geogr., vol. 18, no. 4, p. 133-140, pIs.
15-16.
Khomenko, I., 1934: The stratigraphy of the Tertiary675

beds of the southwestern coast of the Schmidt
Peninsula (northern Sakhalin). Trans. Geol.
Orl Inst., Ser. A, pt. 40, p. 12-85, pIs. 1-19. (inRussian with English sl,lmmary).
Krishtofovich, L.V., 1964: Molluscs from the Tertiary deposits of Sakhalin. Trans. All Union

Petrol. Sci.-Res.

Geol.-Exp. Inst. (VNIGRI),

vypusk 232, p. 1-344, pIs. I-55. (in Russian).
Kubota, K., 1950: Illustrated Cenozoic fossils ofnorthern Japan, 9. Fossil Pectinidae of Setana
Series. Cenoz. Res., no. 6, p.94-100, pIs. 8-9.
(in Japanese).

Kuroda, T., 1931: Fossil Mollusca. In, Homma, F.,

Shinano Chubu Chishitsu-shi (Geology of Central Shinano), pt. 4, p. 1-90, pIs. 1- 13. Kokinshoin, Tokyo. (in Japanese).
MacNeil, F.S., 1967: Cenozoic pectinids of Alaska,
Iceland, and other northern regions. U.S. Geol.
Surv. Prof Pap. 553, p. I-57, pIs. 1-25.
Masuda, K., 1962a: Tertiary Pectinidae of Japan.
Sci. Rep., Tohoku Univ., 2nd Ser., vol. 33, no. 2,
p. 117-238, pIs. 18-27.
- - , 1962b: Notes on the Tertiary Pectinidae ofJapan. Ibid., Spec. Vol., no. 5, p. 159-193.
- - , 1973: Chlamys cosibensis (Yokoyama) of thenorthern Pacific. Ibid., no. 6, p. 109-116, pIs. 89.
- - , 1980: Pliocene biostratigraphy in Japan basedon pectinids. Saito Ho-on Kai Mus., Res.
Bull., no. 48, p. 9-23, pIs. 2-3.
- - , 1986: Note on origin and migration of Cenozoic pectinids in the northern Pacific.
Palaeont. Soc. Japan, Spec. Paper, no. 29, p. 95110, pIs. 7-10.
- - and Sawada, Y., 1961: Some new Tertiary
pectinids from southwestern Hokkaido, Japan.
Japan. Jour. Geol. Geogr., vol. 32, no. I, p. 1929, pI. 4.
Nomura, S. and Hatai, K., 1935: Pliocene Mollusca
from the Daishaka shell-beds in the vicinity ofDaishaka, Aomori-Ken, Northeast Honshu,
Japan. Saito Ho-on Kai Mus., Res. Bull., no. 6,
p. 83-142, pIs. 9-13.
Ogasawara, K., 1986: Paleoenvironmental significance of the late Cenozoic "Astarte" (Bivalvia)
in the northern Pacific region. Monogr.
Mizunami Fossil Mus., no. 6, p. 183-198, pIs. 21,

22. (in Japanese with English abstract).
- - , Masuda, K. and Matoba, Y., 1986: Neogene

and Quaternary molluscs from the Akita Oilfield, Japan. Commemorative Volume of Prof.
T. Takayasu's Retirement. 310 p., 85 pIs. (inJapanese).
Omori, M., 1977: Molluscan fossils from the socalled "Sawane Formation", Sado Island, withspecial description of Pectinidae. Publ. SadoMus., no. 7, p. 63-76, pIs. 1-5. (in Japanese with

676

Kazutaka Amana

English abstract).
Otuka, Y., 1939; Mollusca from the Cainozoic System of eastern Aomori Prefecture, Japan. Jour.
Geol. Soc. Japan, vol. 44, no. 544, p. 23-31, pI. 2.
Shikama, T. and Ikeya, N., 1964; On the variation ofChlamys islandica from a lower part of Setana
Formation. Sci. Rep., Yokohama Natn. Univ.•
Ser. 2, no. II, p.29-54, pis. 1-2.
Siodkewitsch, W.S., 1938; Tertiary Pelecypod a fromthe Far East. USSR A cad. Sci.. Moscow and
Leninglad, vol. 10, no. 3, fasc. 18, p. 1-308, vol.
10, no. 3, fasc. 19, p. 1-275, pis. 1-106.
Stanley, S.M., 1986; Population size, extinction, andspeciation; the fission effect in Neogene
Bivalvia. Paleobiology, vol. 12, no. I, p. 89-110.
Tomizawa, T., 1958; Studies on fossils from theKami-Minochi district, Nagano Prefecture. In
Yagi, T. and Yagi, K., Geology of KamiMinochi-gun, p. 317-347, pis. 1-14. Kokin-shoin,
Tokyo. (in Japanese).
Uozumi, S. and Akamatsu, M., 1975; Pliocene
pectinids from Southwest Hokkaido, Japan.
- Chlamys islandicus-. Jour. Fac. Sci.. Hok-kaido Univ., Ser 4, vol. 17, no. I, p. 27-46.
- - , - - and Takagi, T., 1986; TakikawaHonbetsu and Tatsunokuchi faunas (Fortipecten
takahashii-bearing Pliocene faunas). Palaeont.
Soc. Japan. Spec. Paper, no. 29, p. 211-226, pis.
19-20.
Vermeij, GJ., 1986; Survival during biotic crises;
The properties and evolutionary significance ofrefuges. In, Elliott, O.K. ed., Dynamics ofextinction, p. 231-246. John Wiley & Sons, NewYork.
Yokoyama, M., 1925a; Molluscan remains from theuppermost part of the Joban Coal-field. Jour.
Coli. Sci., Imp. Univ. Tokyo, vol. 45, art. 5, p. 134, pis. 1-6.
- - , 1925b; Tertiary Mollusca from Shinano andEchigo. Jour. Fac. Sci., Imp. Univ. Tokyo. sec.
2, vol. 1, pt. 1, p. 1-23, pis. 1-7.
Zhidkova, L.S., Kuzina, LN., Lautenshleger, F.G. andPopova, L.A., 1968; Atlas of molluscs from theUpper Miocene and Pliocene in Sakhalin.
Acad. Sci. USSR, Siberian Section, p. 1-179, pis.
1-50. (in Russian).

Nagano ~!I!f, Ogikubo :fJ(~1*, Orihashi tfTm, Shigarami 1ffiI, Arakurayama m:~Ul, Setanai!¥JjfJilj, Oaishaka *~~.
i¥tfT~~~1~JiU~ Chlamys ~ (=*j(~) O)~~,ti; ~!I!f~~tflflOYf$I.If~*1t:fJ(~1*1i
iJ'i?~~ < 0) Chlamys iJ~1*~~nt.:: • .:ni?O)~;;t>:I;):, *0) 6{1f;.:il'IJJE~n.Q. -tid:b"t:>,Chlamys (Chlamys) cosibensis (Yokoyama), C. (C.) ingeniosa tanakai Akiyama, C. (C.)
foeda (Yokoyama), C. (C.) insolita (Yokoyama), C. ("C.") lioica shigaramiensis Amano etKarasawa, C. (Leochlamys) tanassevitschi (Khomenko) -C'ib.Q. ':0)'5"t:>, Chlamys
tanassevitschi 1;):{ttiIE C. daishakaensis, C. iwakiana t ~ -C ~ t.::{I"t'ib I), :fJ(~1*liiJ' i?

n1;):4@]*)]~-C~7F~ nt.:: .
.: O)~ f;.:{liJ~~ < Ji!.i? n.Q ~EE t l., -C, of 0)7t:flJ/'('?' -:/ ~ ~H~rs' iJ,~;t i? n.Q.
Chlamys lioica shigaramiensis ~ C. tanassevitschi I;): J:: I) ~ <, *~"t' ib -:J t.:: t ~;t i? n.Q
tfTmrtu~4m~0)~tjffi~tili:J:gtf;.:ll.&i?n, c. foeda 1;):J¥j*~f;.:~'&i?n-C~'.Q. it.::, 6{1r:p,

Chlamys ingeniosa tanakai, C. insolita. C. lioica shigaramiensis 1;):r:p~i!tO)JlH{I"t',

1.If~

i!tr:p~i"t';;t>:~:J:gt~illO)*~id:~ • • ~~~O)Ut.::. U~O)J::'5id:.o).h7t~, r:p~i!t~O){ltl.lf~i!t~O){lO)ifi\il"f;.:J:: I), ;;t>:tili.O) Chlamys O)~~ttiJ'~< id:-:J-C~'.Q.
::R:!I!f~~Trans. Proc. Palaeont. Soc. Japan, N.S., No. 176, pp.677-678, December 30, 1994

SHORT NOTES

32. TAXONOMIC NOTE ON THE STROMATOPOROID
AND RUGOSE CORAL GENERA LABECHIELLA,LABECHIELLATA AND MAZAPHYLLUM*
KEI MORI
Institute of Geology and Paleontology,
Tohoku University, Sendai, 980

The history of the proposal of the genus
Labechiella is confusing. It was proposed asa subgenus of Labechia by Yabe andSugiyama (1930, p. 54) and Labechia serotina
Nicholson (1886) from the Silurian of England was chosen as the type species.
Sugiyama (1939, p. 443) proposed Labechiellaagain without commenting on the previous
study of Yabe and Sugiyama (1930) anddescribed a new type species, Labechiellaregularis from the Silurian of Japan. The
next year the same description of the genus
Labechiella and L. regularis. was publishedby Sugiyama (1940, p. Ill). It is evident that
Labechiella Sugiyama (1939) is a juniorhomonym of Labechiella Yabe and Sugiyama(1930). In 1941 Sugiyama (1941, p.75)
wrote the following concerning the genus
Labechiellata: "In a recent paper, the writerestablished a new stromatoporoid, Labechiellata based upon Labechiellata regularis from
the Middle Gotlandian deposits of the Kitakami Mountainland." Although Labechiellata has long been considered to be simply alapsus memoriae for the genus Labechiella(Galloway, 1957, FlUgel and Fliigel-Kahler,1968 and Mori, 1973), the proposal of thisnew generic name produced further confusion.
Yabe and Sugiyama (1930) in the paper
proposing the subgenus Labechiella, also

proposed the species Labechia regularis fromthe Ordovician of China. Judging from thegross skeletal structures of the holotype(lGPS colI. cat. no. 37684, monotypic), it
does not belong to Labechia, but to Labechiella, because the horizontal structure isdominantly composed of horizontal cysts.
In the genus Labechiella, the specific nameregularis is therefore preoccupied by
Sugiyama's (1939) use of the name for the
Silurian species. Thus Labechiella regularis
Sugiyama (1939) became a secondary homonym of Labechiella regularis (Yabe andSugiyama, 1930). To resolve the homonymy,
Webby (1979) proposed the new name Labechiella sugiyamai for the former (Silurian)species. Through the reexamination of theholotype specimen of Labechiella sugiyamai(lGPS colI. cat. no. 50593), however, it
became evident that the type specimen is nota stromatoporoid, but a fragment of a rugose
coral which was described as Mazaphyllum
mirum Kato (Kato, 1982, p. 390, pI. 61, figs. I,
2; text-fig. lA-C). Both specimens comefrom exactly the same locality; Higuchizawa,
Hikoroichi, Ofunato City, Iwate Prefecture.
The rugose coral genus Mazaphyllum was
first proposed by Crook (1955) and was basedon M. cortisjonesi from the Silurian of New
South Wales. The specimens described by
Kato (1982) as a cystiphyllid coral fromJapan certainly belong to the same group
described by Crook (1955). Therefore, fol-

*Received July 5, 1994; accepted September 9, 1994
677

Kei Mod678

lowing the code of nomenclature, it is concluded that (1) Labechiella sugiyamai
Webby is invalid as a stromatoporoid species,(2) contrary to the previous opinions, thespecific name Labechiellata regularis is validand M. mirum becomes a junior subjectivesynonym of the former, and (3) the genericname Mazaphyllum is a synonym of Labechiellata. Thus it is unfortunate that Labechiellata, once proposed as a stromatoporoid
genus, must be used as a genus of rugose
corals, and that the type specimens of Labechiellata regularis comprise a collection ofsmall pieces of the corallum and do not show
all the features of a complete cystiphyllid
rugose coral.
I thank Professor M. Kato, Hokkaido University and Professor Colin W. Stearn,
McGill University, for their comments andreviewing the manuscript.
References
Crook, K.A.W., 1955: Mazaphyllum, a new cystiphyllid coral from the Silurian of New South
Wales. Jour. Paleont., vol. 29, p. 1052-1056.
Fltigel, E. and Fliigel-Kahler, E., 1968: Stromatoporoidea (Hydrozoa Palaeozoica), Fossilium
Catalogus I: Animalia, pars 115-116. Dr. W.

Junk N.V., Den Haag.
Galloway, J.J., 1957: Structure and classification of
the Stromatoporoidea. Bull. A mer. Paleont.,
vol. 37, no. 164, p. 341-370.
Kato, M., 1982: Mazaphyllum (Rugosa) from the
Silurian of Japan. Trans. Proc. Palaeont. Soc.
Japan, N.S., no. 127, p. 386-392.
Mori, K., 1973: Note on Kitakamiia and Labechiellata, invalid names of Stromatoporoidea. Sci.
Rep., Tohoku Univ., 2nd ser., Spec. Vol., no. 6,
p.401-402.
Nicholson, H.A., 1886: A monograph of the British
stromatoporoids. 234 p. Paleont. Soc. London.
Sugiyama, T., 1939: Geological and geographicaldistribution of the stromatoporoids from Japan,
with notes on some interesting forms. Jubi/.
Public. Commem. Prof Yabe's 60th birthday,vol. I, p.427-456.
- - , 1940: Stratigraphical and paleontologicalstudies of the Gotlandian deposits of the Kitakami Mountainland. Sci. Rep., Tohoku Imp.
Un iv. , 2nd ser., vol. 21, p. 82-146.
- - , 1941: On a new form of the genus Labechiellata from Tyosen (Korea). Jour. GeoL Soc.
Japan, vol. 48, no. 576, p.75-77.
Webby, B.D., 1979: The Ordovician stromatoporoids. Proc. Linn. Soc. N.S. W., vol. 103(2), p.
83-121.
Yabe, H. and Sugiyama, T., 1930: On some Ordovician stromatoporoids from South Manchuria, North China and Chosen (Korea), with noteson two new European forms. Sci. Rep., Tohoku
Imp. Univ., 2nd ser., vol. 14, p.47-62.

679

SYSTEMATIC INDEX(New Series No. 169-N o. 176)

Protoctista
Page
Funakawa, Satoshi: Plagiacanthidae (Radiolaria) from the Upper Miocene ofeastern Hokkaido, Japan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
Hisayoshi, Ueno, Katsumi and Sashida, Katsuo: Lower Permian
fusulinaceans from Ban Phia, Changwat Loei, northeastern Thailand.
Iryu, Yasufumi and Matsuda, Shinya: Taxonomic studies of the Neogoniolithon
fosliei complex (Corallinaceae, Rhodophyta) in the Ryukyu Islands.
Kobayashi, Fumio: Carboniferous foraminifers from the exotic limestone blocks
in the Itsukaichi District, southern Kanto Mountains, Japan. . . ....... . ..

Igo,

15
426
618

Matsumaru, Kuniteru, Thein, Myint and Ogawa, Yujiro: Early Miocene(Aquitanian) larger Foraminifera from the Shimizu Formation, Ashizuri
Cape, Kochi Prefecture, Shikoku Japan ................................ .
Nishi, Hiroshi, Elewa, Ashraf M.T. and Ishizaki, Kunihiro: Planktonic foraminiferal biostratigraphy of Upper Paleocene to Middle Eocene sequences inthe Eastern Desert area, Egypt. ......................................
Sada, Kimiyoshi and Danner, Wilbert R.: A large species of Verbeekina, V. sp. A,
from the Taishaku Limestone in Hiroshima Prefecture, west Japan. ......
Sakagami, Sumio and Mizuno, Yoshihiro: Discovery of Middle Pennsylvanian
fusulinaceans and conodonts from the Copacabana Group in the Lake
Titicaca region, Bolivia. ............................................
Sugiyama, Kazuhiro: Skeletal structures of Lower and Middle Miocene lophophaenids (Radiolaria) from central Japan. ............................

521
401

484
44

Veno, Katsumi: Levenella, a new name for Levenia Veno, 1991 (Foraminiferida,
Fusulinacea), non Gray, 1847.········································
Veno, Katsumi and Igo, Hisayoshi: Upper Carboniferous foraminifers from Ban
Na Din Dam, Changwat Loei, northeastern Thailand. ..................

405
213

Ueno, Katsumi and Mizuno, Yoshihiro: Middle and Upper Carboniferous
fusulinaceans from the Taishaku Limestone Group, southwest Japan. .... 133
Veno, Katsumi and Sakagami, Sumio: Middle Permian foraminifers from Ban
Nam Suai Tha Sa-at, Changwat Loei, northeast Thailand. .............. 277
Xu, Xuedong and Ujiie, Hiroshi: Bathyal benthic foraminiferal changes during thepast 210,000 years: Evidence from piston cores taken from seas south ofIshigaki Islands, southern Ryukyu Island Arc. ........................ 497
Yanagisawa, Yukio: Phylogenetic significance of a new araphid diatom species,

680

Delphineis kamenooensis sp. nov. ....................................

251

Yanagisawa, Yukio: Initial valves of the Miocene extinct diatom genus Denticulopsis Simonsen. ...................................................... 329
Yanagisawa, Yukio: Mediaria magna Yanagisawa, sp. nov., a new fossil arphid
diatom species useful for Middle Miocene diatom biostratigraphy.
Yanagisawa, Yukio: Koizumia Yanagisawa gen. nov., a new marine fossil araphid
diatom genus. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

411
591

PoriferaKano, Akihiro, Lee, Dong-jin, Choi, Duck Keun and Yoo, Chan-Min: Ordovician(Llanvirnian) stromatoporoids from the Youngwol area, southern Korea.

..................................................................

449

Mori, Kei: Taxonomic note on the stromatoporoid and rugose coral genera
Labechiella, Labechiellata and Mazaphyllum . ......................... .

677

Mollusca
Amano, Kazutaka: Diveristy of Chlamys (Bivalvia) from the Pliocene Ogikubo
Formation, central Japan. ..........................................

661

Amano, Kazutaka, Vermeij, Geerat J. and Narita, Ken: Early evolution anddistribution of the gastropod genus Nucella, with special reference to
Miocene species from Japan. ........................................

237

Ehiro, Masayaki: Spathian ammonoids Metadagnoceras and Keyserlingites fromthe Osawa Formation in the southern Kitakami Massif, Northeast Japan.
229
Maeda, Haruyoshi: Dimorphism of Late Cretaceous false-puzosiine ammonites,
Yokoyamaoceras Wright and Matsumoto, 1954 and Neopuzosia Matsumoto,1954.............................................................. .

97

Nobuhara, Takami: The relationship between bathymetric depth and climatechange and its effect on molluscan faunas of the Kakegawa Group, central
Japan. ............................................................

159

Noda, Yoshikazu and Hoyanagi, Koichi: Molluscan fauna from the Miocene
Meshikuni Formation on Rebun Island, northern Hokkaido. . . . . . . . . . . . .
Tanabe, Kazushige, Landman, Neil H. and Mapes, Royal H.: Early shell featuresof some Late Paleozoic ammonoids and their systematic implications.
..................................................................

384

Yuki, Yoshio: An inquiry into the mechanics of trigoniid hinge system. ......

650

311

681

Arthropoda

Collins, Joe S.H., Kanie, Yasumitsu and Karasawa, Hiroaki: Late Cretaceous
crabs from Japan. ..................................................

292

Irizuki, Toshiaki: Morphology and taxonomy of some Japanese hemicytherin
Ostracoda - with particular reference to ontogenetic changes of marginal
pores-. ..........................................................

186

Yumoto, Michiaki: The shell structure of the carapace in Xestoleberis hanaii
Ishizaki (Crustacea, Ostracoda). ......................................

638

Conodonta

Koike, Toshio: Skeletal apparatus and its evolutionary trends in a Triassic
conodont Ellisonia dinodoides (Tatge) from the Taho Limestone, southwest
Japan. ............................................................

382

Mammalia

Shimada, Kenshu and Inuzuka, Norihisa: Desmostylian tooth remains from the
Miocene Tokigawa Group at Kuzubukuro, Saitama, Japan. ............

553

PalaeobotanySun, Ge, Nakazawa, Takashi, Ohana, Tamiko and Kimura, Tatsuaki: Two Neozamites species (Bennettitales) from the Lower Cretaceous of Northeast
China and the Inner Zone of Japan. . ... .... .. ... . .. . . . ..... . . . . . . .... 264
Tanai, Toshimasa and Uemura, Kazuhiko: Lobed oak leaves from the Tertiary of
East Asia with reference to the oak phytogeography of the Northern
Hemisphere. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 343
Zhao, Li-Ming, Ohana, Tamiko and Kimura, Tatsuaki: A fossil population of
Ginkgo leaves from the Xingyuan Formation, Inner Mongolia. ..........

73

Biogenic Texture

Machiyama, Hideaki: Discovery of microcodium texture from the Akiyoshi Limestone in the Akiyoshi Terrane, Southwest Japan. ...................... 578

682

INDEX OF GENERA AND SPECIES
Notes: Words listed are names of genus and species groups which are described,
discussed or illustrated in the articles in Transactions and Proceedings of PalaeontologicalSociety of Japan, New Series, No. 169 to No. 176. Words in bold-type are names of newly
proposed taxa.

cA

Abditodendrix pseudothalmanni .......... 508, fig. 6
Acarinina aspensis ...................... 538, fig. 7
A carin ina bullbrooki .................... 538, fig. 6
Acarinina colomi ............................ 538
Acarinina convexa ............................ 539
A carinina densa .............................. 539
Acarinina esnaensis .......................... 539
A carin ina mckannai .................... 539, fig. 6
Acarinina pentacamerata camerata . ....... 539, fig. 7
Acarinina pentacamerata pentacamerata .. 539, fig. 7
Acarinina praeangulata .................. 540, fig. 7
A carin ina praeangulata .................. 540, fig. 7
Acarinina soldadoensis .................. 540, fig. 6
Acarinina spinuloinftata .................. 540, fig. 6
Alabamina? rugosa ................... . 516, fig. 10
A mphiplecta ................................. .462
Amphilecta acrostoma . .................. .462, fig. 6
A mussiopecten praesignis ................ 171, fig. 7
A nisocorbula scaphoides .................. 171, fig. 7
Archaeopus ezoensis .................. 304, figs. 4, 5
A ristoceras sp. . ......................... 390, fig. 4
Arkanites relictus . ....................... 389, fig. 3
A rtinskia electraensis .................... 392, fig. 5
Astrononion novozealandicum ............ 514, fig. 9
B

Baffinicythere sp. 1 ...................... 188, fig. 2
Baffinicythere sp. 2 ...................... 188, fig. 2
Baffinicythere sp. 3 ...................... 188, fig. 2
Baryspira sua vis ........................ 173, fig. 8
Bisatoceras sp ........................... 390, fig. 4
Biwaella ? sp. . ......................... 219, fig. 4
Bolivina decussata ...................... 508, fig. 6
Bolivina pusilla .......................... 508, fig. 6
Bolivina sp. . ........................... 508, fig. 6
Botryopera .................................... 60
Botryopera (?) leptostraca ................ 60, fig. 14
Botryopera (?) whitei .............. 63, fig. 14, 16, 17
Botryopera (?) sp. A .................... 65, fig. 17
Bulimina aculeata ...................... 508, fig. 6

Cassidulina cf. C. neocarinata ............ 512, fig. 8
Cassidulina norcrossi .................... 512, fig. 8
Cassidulina norvangi .................... 512, fig. 8
Catapsydrax africana ........................ 540
Catapsydrax hardingae ...................... 540
Catapsydrax simulans ........................ 541
Ceratocyrtis .................................. 69
Ceratocyrtis ................................. .463
Ceratocyrtis histricosus ................. .463, fig. 7
Ceratocyrtis multicornus ............... .464, fig. 7
Ceratocyrtis stoermeri .................... 69, fig. 20
Ceratocyrtis sp. aff. C. histricosa ...... 69, figs. 20, 23
Ceratocyrtis sp. . ....................... 464, fig. 7
Chiloguembelina crinita .................. 541, fig. 8
Chiloguembelina cubensis ...................... 541
Chiloguembelina martini ...................... 541
Chiloguembelina midwayensis midwayensis 541, fig. 8
Chlamys (Chlamys) ingeniosa tanakai .... 665, fig. 3
Chlamys (Chlamys) insolita .............. 665, fig. 3
Chlamys (Leochlamys) tanassevitschi .. 666, figs. 4, 5
Chlamys satoi .......................... 171, fig. 7
Cibicides cf. C. refulgens .................. 510, fig. 7
Clathrocorys (?) sp .................... .478, fig. 15
Clementia papyracea .................... 171, fig. 7
Corythomelissa .............................. 476
Corythomelissa horrida . ................. 476, fig. 14
Crenulilimopsis oblonga .................. 173, fig. 8
Crimiteselkoensis ........................ 390, fig. 4
Cryptogyrus .................................. 65
Cryptogyrus trachylobus ............ 65, figs. 19, 20
Crytopecten vesiculosus .................. 173, fig. 8
Cucullaea labiosa granulosa ............. . 171, fig. 7
Cycladicama cumingii .................. 173, fig. 8
D

Daishakacythere . ............................. 202
Daishakacythere abei ................ 204, figs. 2, 12
Daishakacythere posterocostata ...... 204, figs. 2, 12
Daishakacythere sp. 1 ................ 206, figs. 2, 12
Darvasites contractus .................... 25, fig. 5
Darvasites ingavati ...................... 29, fig. 5
Delphineis kamenooensis . ............. 256, figs. 3, 4

683

Delphineis miocenica .................. 258, figs. 3, 7
Desmostylus. sp ................ 566, figs. 16, 17,23
Desmostylus? .......................... 567, fig. 18
Diaulax yokoii ........................ 295, fig. 2
Diplognathodus orphanus ............... .489, fig. 4Dunbarula ? sp. . ....................... 284, fig. 5
E

Ellisonia .................................... 375
Ellisonia dinodoides . ..................... 376, fig. 7
Endothyra igoi ........................ 620, fig. 3
Ennucula niponica ...................... 173, fig. 8
Eodorippe binodosa . ..................... 303, fig. 2
Eostajfella kamiyoza wensis .............. 624, fig. 3
Eostaffella yowarensis .................... 627, fig. 3
Eothalassoceras inexpectans .............. 390, fig. 4
Epistominella exigua .................... 510, fig. 7
Epistominella levicula .................... 510, fig. 7
Eponides lamarckianus .................. 510, fig. 7
Eponides tenerus ........................ 510, fig. 7
Eponides tumidulus .................... 516, fig. 10
Euscenarium ............................... .477
Euscenarium sp.aff.E. tricolpium ............... .477
Euscenarium (?) sp. . ........................ .477
Evolvocassidulina brevis .................. 514, fig. 9
F
Favocassidulina favus . ................... 512, fig. 8
Finmarchinella hanaii .................. 188, fig. 2
Finmarchinella japonica .................. 188, fig. 2
Finmarchinella nealei .................... 188, fig. 2
Finmarchinella rectangulata .............. 188, fig. 2
Finmarchinella subrectangulata ...... 206, figs. 2, 13
Finmarchinella uranipponica .............. 188, fig. 2
Fursenkoina cedrosensis .................. 512, fig. 8
Fusulina quasicylindrica . ................. 147, fig. 9
Fusulinella bingoensis .................. 141, fig. 6G

Ginkgo manchurica .................... 75, figs. 2-6
Glaphyrites clinei ........................ 389, fig. 3
Glaphyrites hyattianus .................. 389, fig. 3
Glaphyrites warei ...................... 386, fig. 2
Globigerina lozanoi ...................... 541, fig. 6
Globigerina officinalis ........................ 541
Globigerina parva ............................ 541
Globigerinatheka index index ···························542
Globigerinatheka mexican a kugleri ............ 542
Globigerinatheka mexican a mexican a .......... 542"Globigerinoides" higginsi ................ 542, fig. 6
Globocassidulina bisecta .................. 512, fig. 8
Globocassidulina subglobosa .............. 512, fig. 8
Glycymeris cisshuensis .................. 319, fig. 8
Glycymeris idensis ...................... 321, fig. 9
Glycymeris rotunda . ..................... 173, fig. 8
Goniatites sp. . ......................... 386, fig. 2

Goniatites choctawensis .................. 386, fig. 2
Guembelitria columbiana ...................... 542
Gyroidina sp. . ......................... 514, fig. 9H
Hantkenina mexicana ........................ 543"Hastigerina" cf. bolivariana .................. 543
Hemicythere emarginata ................ 188, fig. 2
Hemicythere kitanipponica . ............... 188, fig. 2
Hemicythere ochotensis .................. 188, fig. 2
Hemicythere orientalis .................. 188, fig. 2
Hemoceras subglobosum . ................. 392, fig. 5
Hydrolithon onkodes ................... .443, fig. 8

Idiognathodus delicatus ................. .491, fig. 4
Jligulites dagmarae .................... 152, fig. 10
ligulites grandis ...................... 224, fig. 6
ligulites sp ............................. 152, fig. 10
lohnnealella nopporoensis .............. 188, fig. 2
K

Karreriella hanzawai .................... 508, fig. 6
Katahiraia aspera ...................... 334, fig. I
Katahiraia oblonga ...................... 332, fig. I
Katahiraia pauperata .................... 332, fig. I
Keyserlingites ................................ 234
Keyserlingites cf. K. middendorffi ...... 234, figs. 2, 3
Koizumia .................................... 599
Koizumia adaroi .................... 600, figs. 8, 9
Koizumia akibae . ................... 604, figs. 8, 12
Koizumia tatsunokuchiensis .......... 606, figs. 8, 14
L

Labechiella .................................. 675
Labechiella regularis .................. 453. figs. 3, 4
Labechiellata ................................ 675
Levenella ................................... .405
Levenia ...................................... 405
Limopsis tajimae ........................ 173, fig. 8
Lophophaena ................................ 465
Lophophaena simplex . ................... 465, fig. 8
Lophophaena triangula .................. 466, fig. 8
M
Makiyamaia coreanica .................. 173, fig. 8
Marimoum ................................. .468
Marimoum robustum ................... .468, fig. 9
Mazaphyllum ................................ 675
Mediaria magna ................... .412, figs. 3, 4Mediaria splendida f. splendida ......... .417, fig. 3
Mediaria splendida f. tenera .......... 491, figs. 3, 8
Melonis barleeanum .................... 516, fig. 10
Melonis sphaeroides .................... 516, fig. 10

684

Metadagnoceras otoyoshiense . ......... 232, figs. 2, 3
Metahomola brevis . ..................... 297, fig. 2
Minojaponella (Minojaponella) sp ........... 25, fig. 3
Minojaponella (Russiella) ? sp ............. 282, fig. 5
Miogypsinoides dehaartii ................ 5, figs. 2, 3
Miogypsina sp ............................. 8, fig. 3
Mizuhopecten tokyoensis hokurikuensis .... 171, fig. 7
Montiparus matsumotoi .................. 632, fig. 4
Morozovella angulata .................... 543, fig. 7
Morozovella bandyi .......................... 543
Morozovella conicotruncata .............. 543, fig. 7
Morozovella occlusa acutispira ............ 543, fig. 8
Morozovella occlusa occlusa .............. 544, fig. 8
Morozovella simulatilis ........................ 544
Morozovella spinulosa .................... 544, fig. 8
Morozovella velascoensis acuta ................ 544
Morozovella velascoensis parva ............ 544, fig. 8
Morozovella velascoensis velascoensis ...... 544, fig. 8
Muricoglobigerina senni ...................... 544
Mytilus tichanovitchi ....... ............. 324, fig. 10
NNankinella ? loeiensis .................... 38, fig. 8
Nankinella sp. . ......................... 154, fig. 5
Nankinella sp. . ......................... 284, fig. 5
Nankinella spp. . ....................... 227, fig. 4
Nassaria magnifica ..................... . 173, fig. 8
Nassarius dorsatus ...................... 171, fig. 7
Nassarius siquijorensis .................. 173, fig. 8
Neilonella coix .......................... 173, fig. 8
Nemocardium samarangae .............. 173, fig. 8
Neofusulinella ? peudogiraudi
282, fig. 5
Neofusulinella sp ......................... 282. fig. 5
Neognathodus medadultimus ............ 491, fig. 4
Neogoniolithon fosliei .............. 439, figs. 2-6, 8
Neogoniolithon tenuicrustaceum .............. 441
Neogoniolithon sp. A .................... 440, fig. 8
Neopuzosia .................................... 98"Neopuzosia haboroensis" ...................... 105"Neopuzosia ishikawai" . ....................... 105"Neopuzosia japonica" ........................ 105
Neotrigonia margaritacea .............. 650, fig. 1, 4
Neozamites elongatus ............ 267, figs. 3, 4, 5, 6
Neozamites intermedius .............. 272, figs. 3, 4
Nephrolepidina paraejaponica ............ 8, figs. 2, 3
Normanicythere japonica ................ 188, fig. 2
Notopocorystes (Eucorystes) intermedius . ... 302, fig. 4
Notopocorytes (Notopocorystes) japonicus .. 300, fig. 3
Nucella freycineti saitoi .................. 243, fig. 2
Nucella tokudai ........................ 240, fig. 2

oOblimopa japonica ...................... 171, fig. 7
Obsoletes obsoletus ...................... 630, fig. 7
Obsoletes cr. obsoletus . ................... 146, fig. 8
Occidentoschwagerina chatcalica ........ 153, fig. 10

Onustus exutus ........................ 173, fig. 8
Oridorsalis umbonatus .................. 516, fig. 10
PPaleoparadoxia tabatai ........ 558, figs. 4-8, 19, 21
Paleoparadoxia? tabatai .. 562, figs. 9-12, 19,21,22
Paleparadoxia sp. . ............. 565, figs. 13-15, 20
Pamirina .................................... 19
Pamirina (Levenia) sp ..................... 24, fig. 3
Pamirina (Pamirina) darvasica . ......... 20, figs. 3, 4
Paphia amabilis ........................ 171, fig. 7
Paphia schnelliana ...................... 173, fig. 8
Parafusulina sp. . ....................... 284, fig. 5
Paratolia sp. . ........................... 12, fig. 2
Patagonacythere robursta ................ 188, fig 2
Patagonacythere sasaokensis ........ 208, figs. 2, 13
Peridium .................................... 470
Peridium aff. spinipes ...................... fig. 11
Peridium sp .......................... .471, fig. 11
Pisolina cf. subspherica .................. 284, fig. 5
Pithonoton injiatum .................... 295, fig. 2
Planoendothyra sp. A .................... 624, fig. 2
Planorotalites albeari .................... 544, fig. 7
Planorotalites pseudomenardii ............ 545, fig. 7
Planorotalites pseudoscitula .............. 545, fig. 8
Planorotalites pusilla pusilla .................... 545
Planulina bradii ........................ 510, fig. 7
Planulina wuellerstorfi .................. 510, fig. 7
Presumatrina cf. neoschwagerinoides ...... 287, fig. 4
Profusulinella hinodensis ............ 627, figs. 4, 6
Profusulinella munda ................... .488, fig. 3
Profusulinella sp ......................... 486, fig. 3
Protriticites ova tus ...................... 144, fig. 8
Pseudocubus obeliscus . ................. 51, figs. 7, 8
Pseudodictyophimus .......................... 472
Pseudodictyophimus gracilipes . ........... 472, fig. 12
Pseudodictyophimus tanythorax ........ 473, fig. 12
Pseudodoliolina cr. pseudolepida .......... 286, fig. 4
Pseudoendothyra ? constricta .............. 39, fig. 7
Pseudoendothyra musashiensis ............ 634, fig. 5
Pseudoendothyra ? sp. . ................... 40, fig. 7
Pseudofusulina siamensis ................ 29, fig. 6
Pseudofusulina sp. A ...................... 33, fig. 5
Pseudofusulina sp. B ...................... 33, fig. 6
Pseudofusulina sp. C ...................... 33, fig. 6
Pseudofusulina sp. D ...................... 33, fig. 6
Pseudofusulinella (Kanmeraia) ex gr. pulchra...................................... 143, fig. 7
Pseudofuslinella (Kanmeraia) sp ........... 144, fig. 6
Pseudohastigerina wilcoxensis ............ 545, fig. 8
Pseudoreichelina darvasica ................ 33, fig. 7
Pullenia sp. . ........................... 514, fig. 9
Pulleniella asymmetrica .................. 514, fig. 9

Q
Quercus kobatakei.................. 348, figs. 2, 4

685

Quercus kodairae .................... 350, figs. 2, 4
Quercus sichotensis .................. 352, figs. 4, 5
Quercus ussuriensis ................ 354, figs. 2, 5, 8
R

Rugosochusenella sp. . ................... 222, fig. 4
Rugosofusulina sp. A .................. 153, fig. 10
Rugosofusulina? sp. B .................. 153, fig. 10
Rugosofusulina? sp. . ................... 227, fig. 4
S

Schubertella melonica .................... 24, fig. 3
Schubertella sp. A ........................ 25, fig. 3
Schubertella sp. B ........................ 25, fig. 3
Schubertella sp. . ....................... 141, fig. 5
Schubertella sp. . ....................... 219, fig. 4Siphouvigerina porrecta .................. 508, fig. 6
Sphaerulina cf. croatica .................. 38, fig. 9
Spiroclypeus margaritata .............. 10, figs. 2, 3
Staffella ? ovalis ........................ 35, fig. 9
Staffella sp. A ............................ 37, fig. 8
Staffella sp. . ........................... 284, fig. 5
Staffella? sp. B .......................... 37, fig. 8
Steganocubus ................................ 56
Steganocubus lipus ... ................... 58, fig. 12
Steganocubus subtilis ................ 56, figs. 10, 11
Subbotina bakeri ............................ 545
Subbotina eocaena ............................ 545
Subbotina frontosa boweri ................ 545, fig. 6
Subbotina frontosa frontosa .................... 546
Subbotina hagni .............................. 546
Subbotina inaequispira ........................ 546
Subbotina linaperta .......................... 546
Subbotina pseudoeocaena ...................... 546
Subbotina triangularis ........................ 546
Subbotina triloculinoides ...................... 546
Subbotina velascoensis ........................ 546
Subbotina yeguaensis . ......................... 546
T
Takayanagia delicata ................... . 512, fig. 8
Toriyamaia sp. . ......................... 25, fig. 3
Trifarina angulosa ...................... 508, fig. 6
Tripodocyrtis ................................ 473
Tripodocyrtis elegans ................. .474, fig. 13

Triticites (Rauserites) lucidus ............ 150, fig. 10
Triticites (Rauserites) tuckenbergi ........ 150, fig. 10
Triticites (Triticites) samaricus ............ 222, fig. 5
Triticites (Triticites) sch wageriniformis .... 148, fig. 10
Truncorotaloides collactea .................... 546
Truncorotaloides pseudodubia .................. 547
Truncorotaloides rohri .................. 547, fig. 6
Truncorotaloides topilensis ................ 547, fig. 6
Turborotalia cerroazulensis possagnoensis ........ 547
Turborotalia griffinae ........................ 547
Turborotalia wilsoni .......................... 547
Turritella (Hataiella) cf. sagai ............ 319, fig. 8
U

Urocythereis ? gorokuensis . ............... 188, fig. 2
Uvigerina proboscidea vadescens .......... 508, fig. 6
V

Venericardia panda . ..................... 171, fig. 7
Ventricolaria foveolata .................. 173, fig. 8
Verbeekina verbeeki .................... 286, fig. 4
Verbeekina sp. A ........................ 402, fig. 1
Victoriella conoidea ...................... 11, fig. 2
Vidrioceras sp ........................... 392, fig. 5
X

Xestoleberis hanaii................ 638, figs. 1, 4-6
Y

Yangchenia sp ........................... 282, fig. 5
Y okoyamaoceras .............................. 98
Yokoyamaoceras ishikawai .... 122, figs. 3, 4, 6, 9, 10" Y okoyamaoceras jimboi" .................... 101"Yokoyamaoceras kotoi" ...................... 101"Yokoyamaoceras minimum" .................. 103"Yokoyamaoceras (?) mysticum" .............. 103"Yokoyamaoceras ornatum" .................. 103" Y okoyamaoceras yokoii" .................... 103
Y oshidaia constricta .................... 334, fig. 2
Y oshidaia divergens .................... 334, fig. 2
Y oshidaia loculata ...................... 334, fig. 2
Z

Zeauvigerina aegyptiaca . ................. 547, fig. 8

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNos. 169- 176
1993- 1994

Palaeontological Society of Japan

The calligraphy on the cover for the Japanese title "Nihon Koseibutsu-gakkai Hokoku
Kiji" is the work of Dr. Matajiro Yokoyama, a fatherly figure in Japanese paleontology, who
was Professor of Stratigraphy and Paleontology at the Geological Institute, Imperial
University of Tokyo.
The fossil on the cover is Isocrinus (Chladocrinus) hanaii Oji, an Early Cretaceous(Aptian) crinoid, which was described from the Hiraiga Formation exposed at Haipe,
Tanohata-mura, Shimo-Hei County, Iwate Prefecture, Northeast Japan. (University Museumof the University of Tokyo coil. cat. no. ME6950, paratype specimen, length about II em).

CONTENTS

Number 169 (published April 30, 1993)
TRANSACTIONS
948. Kuniteru Matsumaru, Myint Thein and Yujiro Ogawa: Early
Miocene (Aquitanian) larger Foraminifera from the Shimizu
Formation, Ashizuri Cape, Kochi Prefecture, Shikoku, Japan ...
949. Hisayoshi Igo, Katsumi Ueno and Katsuo Sash ida : Lower
Permian fusulinaceans from Ban Phia, Changwat Loei, northeastern Thailand .......................................... .
950. Kazuhiro Sugiyama: Skeletal structures of Lower and Middle
Miocene lophophaenids (Radiolaria) from central Japan. . .....
951. Li-Ming Zhao, Tamiko Ohana and Tatsuaki Kimura: A fossil
population of Ginkgo leaves from the Xingyuan Formation,
Inner Mongolia. ..........................................
952. Haruyoshi Maeda: Dimorphism of Late Cretaceous falsepuzosiine ammonites, Yokoyamaoceras Wright andMatsumoto, 1954 and Neopuzosia Matsumoto, 1954. ... ..... . .
PROCEEDINGS ........................................

Page Figures

1-14

1-4

15-43

1-9

44-72

1-23

73-96

1-7

97-1281-16

129-132

Number 170 (published June 30, 1993)
TRANSACTIONS
953. Katsumi Ueno and Yoshihiro Mizuno: Middle and Upper
Carboniferous fusulinaceans from the Taishaku LimestoneGroup, southwest Japan ..................................
954. Takami Nobuhara: The relationship between bathymetric
depth and climate change and its effect on molluscan faunas of
the Kakegawa Group, central Japan....... ..... ... ..... . . ..
955. Toshiaki Irizuki; Morphology and taxonomy of some Japanese
hemicytherin Ostracoda - with particular reference toontogenetic changes of marginal pores- ....................

133-158

1-10

159-1851-9

186-2121-13

Number 171 (published September 30, 1993)
TRANSACTIONS
956. Katsumi Ueno and Hisayoshi Igo: Upper Carboniferous foraminifers from Ban N a Din Dam, Changwat Loei, northeastern
Thailand ................................................
957. Masayuki Ehiro: Spathian ammonoids Metadagnoceras andKeyserlingites from the Osawa Formation in the southern
Kitakami Massif, Northeast Japan. . . . . . . . . .. . . . . . . . . . . . . . ..
958. Kazutaka Amano, Geerat J. Vermeij, and Ken Narita: Early
evolution and distribution of the gastropod genus Nucella, withspecial reference to Miocene species from Japan. . . . . . . . . . . . ..
PROCEEDINGS ........................................

213-2281-6

229-2361-3

237-2481-4

249-250

Number 172 (published December 30, 1993)
TRANSACTIONS
959. Yukio Yanagisawa: Phylogenetic significance of a new araphid
diatom species, Delphineis kamenooensis sp. nov. ............
960. Ge Sun, Takashi Nakazawa, Tamiko Ohana, and Tatsuaki
Kimura: Two Neozamites species (Bennettitales) from theLower Cretaceous of Northeast China and the Inner Zone ofJapan ..................................................
961. Katsumi Ueno and Sumio Sakagami: Middle Permian foraminifers from Ban Nam Suai Tha Sa-at, Changwat Loei,
northeast Thailand. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
962. Joe S.H. Collins, Yasumitsu Kanie, and Hiroaki Karasawa:
Late Cretaceous crabs from Japan. . . . .. . . .. .. . . . . . . . . . . . . ..
963. Yoshikazu Noda and Koichi Hoyanagi: Molluscan fauna from
the Miocene Meshikuni Formation on Rebun Island, northern
Hokkaido. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

251-2631-8

264-276

1-6

277 - 291

1-5

292-3101-5

311-328

Number 173 (published April 30, 1994)
TRANSACTIONS
964. Yukio Yanagisawa: Initial valves of the Miocene extinct
diatom genus Denticulopsis Simonsen ......................
965. Toshimasa Tanai and Kazuhiko Uemura: Lobed oak leaves
from the Tertiary of East Asia with reference to the oakphytogeography of the Northern Hemisphere. ... . ... . . . .....
966. Toshio Koike: Skeletal apparatus and its evolutionary trends
in a Triassic conodont Ellisonia dinodoides (Tatge) from theTaho Limestone, southwest Japan..... .... ..... . .... . ......
967. Kazushige Tanabe, Neil H. Landman and Royal H. Mapes:
Early shell features of some Late Paleozoic ammonoids andtheir systematic implications
SHORT NOTES
30. Kimiyoshi Sada and Wilbert R. Danner: A large species ofVerbeekina, V. sp. A, from the Taishaku Limestone in Hiroshima Prefecture, west Japan ..............................
31. Katsumi Ueno: Levenella, a new name for Levenia Ueno, 1991
(Foraminiferida, Fusulinacea), non Gray, 1847 ..............
PROCEEDINGS ........................................

329-3421-6

343-3651-8

366-3831-8

384-4001-8

401-404

1-2

405
406-410

Number 174 (published June 30, 1994)
TRANSACTIONS
968. Yukio Yanagisawa: Mediaria magna Yanagisawa, sp. nov., a
new fossil arphid diatom species useful for Middle Miocene
diatom biostratigraphy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..
969. Yasufumi Iryu and Shinya Matsuda: Taxonomic studies of the
Neogoniolithon fosliei complex (Corallinaceae, Rhodophyta) in
the Ryukyu Islands ......................................
970. Akihiro Kano, Dong-jin Lee, Duck Keun Choi, and Chan-Min
Y 00: Ordovician (Llanvirnian) stromatoporoids from theY oungwol area, southern Korea. . . . . . . . . . . . . . . . . . . . . . . . . . ..
971. Satoshi Funakawa: Plagiacanthidae (Radiolaria) from theUpper Miocene of eastern Hokkaido, Japan ................

411-4251-8

426-4481-8

449-457

1-4

458-483

1-16

972.

Sumio Sakagami and Y oshihiro Mizuno: Discovery of Middle
Pennsylvanian fusulinaceans and conodonts from the
Copacabana Group in the Lake Titicaca region, Bolivia. . . . ..

484-495

ANNOUNCEMENT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

496

1-4

Number 175 (published September 30, 1994)
TRANSACTIONS
973. Xuedong Xu and Hiroshi Ujiie: Bathyal benthic foraminiferalchanges during the past 210,000 years: Evidence from piston
cores taken from seas south of Ishigaki Islands, southern Ryukyu Island Arc ..........................................
974. Hiroshi Nishi, Ashraf M.T. Elewa, and Kunihiro Ishizaki:
Planktonic foraminiferal biostratigraphy of Upper Paleocene to
Middle Eocene sequences in the Eastern Desert area, Egypt ..
975. Kenshu Shimada and Norihisa Inuzuka: Desmostylian tooth
remains from the Miocene Tokigawa Group at Kuzubukuro,
Saitama, Japan ..........................................
976. Hideaki Machiyama: Discovery of microcodium texture fromthe Akiyoshi Limestone in the Akiyoshi Terrane, Southwest
Japan ..................................................
PROCEEDINGS ........................................

497 - 520I-II

521-5521-8

553-5771-23

578-586

1-5

587-590

Number 176 (published December 30, 1994)
TRANSACTIONS
977. Yukio Yanagisawa: Koizumia Yanagisawa gen. nov., a new
marine fossil araphid diatom genus ........................
978. Fumio Kobayashi: Carboniferous foraminifers from the exotic
limestone blocks in the Itsukaichi District, southern Kanto
Mountains, Japan........................................
979. Michiaki Yumoto: The shell structure of the carapace in
Xestoleberis hanaii Ishizaki (Crustacea, Ostracoda) ..........
980. Y oshio Yuki: An inquiry into the mechanics of trigoniid hinge
system ..................................................

591-6171-16

618-6371-7

638-6491-7

650-660

1-10

Kszutaka Amano: Diversity of Chlamys (Bivalvia) from the
Pliocene Ogikubo Formation, central Japan

661-676

SHORT NOTES
30. Kei Mori: Taxonomic note on the stromatoporoid and rugose
coral genera Labechiella, Labechiellata and Mazaphyllum ....

677-678981.

SYSTEMATIC INDEX .......................................... 679
INDEX OF GENERA AND SPECIES ............................ 682

1-7

~.~~~(1993-1994):tLw f~~~-t:t" I[g~~Eilffif OOlm~~

;J\DlI~~

B11i 11nE (~ffii~)

~WIJ

~a

fflJj$-P.X:'M83 ¥:J\:;

~f1

J\~

lIB

;/]llMi tt~

ffi1%*~O)~fff:~T 7.>Jfm Ii, ~ffiiO)~JfrJ;'H:, )($llf-W¥=flff~JfffIHV]~~ ~ lff:JUI]~ffiii»~ 0)~JfiM3-r ~n -r1t~*To ffl.{£O)JtWJ~ffiiliTgGO)Jm D-rOT

1 /' r;:t, Y7EntJ~~~f±

OO*x?&jl A~~~f±~t:h.1i'IrP.ll El ?&~1W!Jo/J~:; l' /{/,:r. t:;-:fiilllRl*)':\~

0

1!if

E

1W

~

!Jo/J

.y 1 -V :J /' 4j- Iv ?' /' r

WOOEntJ~~~f:I:

EntJjt~OO~~~~f:I:~}!I[l,~.llA t El?&o)1W!Jo/J~-=-#EntJOO~~~~f:I:::. ~-:;7 ,L,./{-7~EI~(717.x~lIIrO

1 9 9 4 if- 12 ~ 27 B

EfJ

1 9 9 4 if- 12 ~ 30 B

~

ISSN

0031-0204

B*"i!l~¥lJq:~~~·*C~

iWTa

JilU
fJ

~fT*

B*rJl1:!jo/]~~:;=ll3 *JjHlltlt*I8:*WYj6 5-16-9
B *q:~nJ~ ~:/? - F'3• ~ 03-5814-5801~.m-lE·~f,ilf

i1a*~lf.

176-1}
2,500 P3

fill tl rtH1i** 18: TO) gg IBJ 8-45~m~I±l!\&EfJJilu~;;:\~tl§

m~~*l'I*tf:022-288-5555 JIOj{ 03-3455-4415

Transactions and Proceedings of the PalaeontologicalSociety of Japan

New Series No. 176

December 30, 1994

CONTENTS
TRANSACTIONS
977.

Yukio Yanagisawa: Koizumia Yanagisawa gen. nov., a new marine fossil
araphid diatom genus ................................................ 591

978.

Fumio Kobayashi: Carboniferous foraminifers from the exotic limestone

979.

Michiaki Yumoto: The shell structure of the carapace in Xestoleberis hanaii

blocks in the Itsukaichi District, southern Kanto Mountains, Japan...... 618

Ishizaki (Crustacea, Ostracoda) ........................................ 638
980.
981.

Yoshio Yuki: An inquiry into the mechanics of trigoniid hinge system.. 650Kazutaka Amano: Diversity of Chlamys (Bivalvia) from the Pliocene Ogikubo Formation, central Japan ........................................ 661

SHORT NOTES
30.

Kei Mori: Taxonomic note on the stromatoporoid and rugose coral genera

Labechiella, Labechiellata and Mazaphyllum.......................... 677

SYSTEMATIC INDEX .................................................... 679
INDEX OF GENERA AND SPECIES ...................................... 682