(ISSN 0031-0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNo. 140

Palaeontological Society of Japan
December 30, 1985

Co-Editors

Hisayoshi 100 and Takashi HAMADA

Officers for 1985-1986
President: Toshimasa TANAI
Honorary President: Teiichi KOBAYASHI
Councillors;

Kiyotaka CHINZEI, Takashi HAMADA, Tetsuro HANAI, Yoshikazu HASEGAWA,

Itaru HAYAMI, Hisayoshi IGO, Junji ITOIGAWA, Tadao KAMEl, Tatsuaki KIMURA,
Tamio KOTAKA, Kei MORI, Ikuwo OBATA, Tsunemasa SAITO, Yokichi TAKAYANAGI,
Toshimasa TANAIMembers of Standing Committee:

Kiyotaka CHINZEI (Membership), Takashi HAMADA (Co-

Editor of Transactions), Yoshikazu HASEGAWA (Foreign Affairs), Itaru HAY AMI(Planning), Hisayoshi IGO (Co-Editor of Transactions), Tatsuaki KIMURA (Finance),
Ikuwo OBATA (General Affairs), Yokichi TAKAYANAGI (Editor of "Fossils"), Juichi
YANAGIDA (Editor of Special Papers)
Secretary: Hiroshi NODA (Editor of Transactions)Auditor: Yoshiaki MA TSUSHIMA

The fossil on the cover is Unuma (Spinunuma) echinatus ICHIKAWA and YAO, a
Middle Jurassic multisegmented radiolaria from Unuma, Gifu Prefecture, central
Japan (photo by A. YAO, x 260).

All communication relating to this journal should be addressed to the

PALAEONTOLOGICAL SOCIETY OF JAPAN
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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 140, pp. 225-239, pIs. 31-34, December 30, 1985

804. RECURRENT MOLLUSCAN ASSOCIATIONS OF THE OMMA-MANGANJIFAUNA IN THE GOJOME-OGA AREA, NORTHEAST HONSHUPART 2. SYSTEMATIC NOTES ON BIVALVE SPECIES*
SEIICHIRO MATSUI
Department of Earth Science, Faculty of Education, Utsunomiya University,
Utsunomiya 321, Japan

Abstract.
described.

Forty-seven species of bivalves from the Gojome-Oga area are

Acila (Truncacila) nakazimai Otuka, 1939, pp ..
26, 27, pI. 2, figs. 9-11.

Systematic notes (continued from Part 1)
Nucula (Leionucula) niponica Smith, 1885

Locality: 1-1 (CMI6396, CM16397); 2-2d
(CMI6398); 2-7 (CM16399); 4-3 (CM16400);
44 (CMI6401); 4-5g (CMI6402); 4-5h (CM16403); 5-5 (CMI6404); 5-13b (CMI6405);
23-2 (CM16406); 26-2c (CMI6407); 34-1 (CM16408).

PI. 31, Fig. 1.
Nucula niponica Smith, 1885, p. 226, pI. 18,
figs. 8, 8a.
Nucula (Nucula) niponica Smith. Otuka, 1936,
pp. 727,728, pI. 41, figs. 1a-b, 2.

Locality: Ogl-l (CM16391, CM16392).

Acila (Truncacila) sp.

Acila (Acila) divaricata (Hinds, 1843)

PI. 31, Fig. 4.

PI. 31, Fig. 2.

Small form of Acila (Truncacila) appears inthe sandy Macoma tokyoensis Association, andis similar to small individuals of Acila nakazimai
in outline and surface ornamentation. The
samples of Acila nakazimai listed above containindividuals larger than 20 mm long or in somecases than 30 mm long, and occur from the
Acila-Turritella, Nuculana and Thyasira bisecta
Associations, while Acila sp. in the Macoma
tokyoensis Association is 11.6 mm long in thelargest individual and usually smaller than 7 mm
long. It can not be decided whether these specimens of Acila represent a distinct species differ
from nakazimai or a dwarf ecophenotype ofnakazimai in shallower sandy bottom.
Locality: 4-2a (CMI6409, CMI6410); 4-2b
(CMI6411); 5-1a (CMI6412); 25-2 (CMI6413).

Nucula mirabilis Adams and Reeve. Yokoyama,
1920, pp. 180, 181, pI. 19, fig. 9.
Acila (Acila) diuaricata (Hinds). Schenck, 1936,
pp. 90-92, pI. 15, figs. 1-10, text-fig. 8(1,2).
Acila nakazimai Otuka. Takayasu, 1962, pI. 1,
fig. 14.

Locality: Og2-2a (CM16393); Og2-4 (CM16394, CM16395).
Acila (Truncacila) nakazimai Otuka, 1939

PI. 31, Fig. 3.

*Received JUly 2, 1984.
225

Seiichiro MATSUI

226

Nuculana sadoensis (Yokoyama, 1926)

PI. 31, Figs. 5, 6.
Leda sadoensis Yokoyama, 1926b, p. 308, pI. 36,
fig. 6.
Nuculana pernula sadoensis (Yokoyama). Suzuki
and Kanehara, 1936, pp. 179, 180, pI. 10,
figs. 1-7; Takayasu, 1962, pI. 1, figs. 9a-b.
Nuculana (Nuculana) pernula sadoensis (Yoko·yama). Oyama, 1951, p. 148, pI. 6, figs. 3a-b.

Suzuki and Kanehara (1936), who examined
the topotype specimens, noted that the surfaceof the species is concentrically very finely
grooved, and that the small area below the umbo
is ornamented by low and fine concentric ribs.
Five specimens examined here have such orna·
mentation and other features also well agree withthe description of Yokoyama (1926b), andSuzuki and Kanehara (1936). This species isvery similar to Nuculana pernula in outline, but
pernula has numerous and fine concentric ribson the whole surface of the shell.
Locality: 2-8 (CM16414); 12-2 (CM16415,
CM16416); Og2-1 (CM16417, CM16418).
Nuculana yokoyamai Kuroda, 1934

PI. 31, Fig. 8.
Leda ramsayi Smith. Yokoyama, 1920, pp. 176,
177, pI. 19, figs. 3a-b.
Nuculana (Thestyleda) yokoyamai Kuroda, 1934,
p. 204; Kaseno and Matsuura, 1965, pI. 7,
fig. 10; Kuroda, Habe and Oyama, 1971, p.
320, pI. 66, fig. 14; Ogasawara, 1977; pI. 5,
fig. 2.

Locality: 2-2c (CM16419, CM16420); 20-1b(CM16421); 26-4 (CM16422); 26-7c (CM16423);
Og2-4 (CM16424).
Nuculana (Robaia) robai (Kuroda, 1929)

PI. 31, Fig. 7.
Leda robai Kuroda, 1929, app. 9, app. 6, figs. 6,
7.
Nuculana robai (Kuroda). Suzuki and Kanehara,
1936, pp. 181, 182, pI. 10, figs. 8-15; Taka·yasu, 1962, pi, 1, figs. 10a-b; Chinzei, 1973,
pI. 14, fig. 10.

Nuculana (Robaia) robai (Kuroda). Habe, 1958a,p.248.
Robaia robai (Kuroda). Habe and Ito, 1965, p.
105, pI. 34, fig. 15.

One right valve and some fragmental shells
are examined. They are characterized by nearlystraight postero·dorsal margin, wide and round
posterior margin and smooth surface of the shell.
They are identical with Nuculana (Robaia) robai(Kuroda).
Locality: 5-11b (CM16425); 5-13c (CM16426); 28-2 (CM16427); Ogl-l (CM16428);
Og2-7 (CM16429).
SacceUa (Costanuculana) onoyamai(Otuka, 1935)

PI. 31, Figs. 9-11.
Nuculana onoyamai Otuka, 1935a, pp. 507,508,
figs. 3(b), 3(c); Otuka, 1935b, p. 881, pI. 55,
figs. 105, 106; Itoigawa, 1958, pI. 1, fig. 2;
Iwai, 1965, p. 23, pI. 14, figs. 3a-4b.
Descnption:-Shell small, subelliptical in out·line, high and thick, attaining 1 mm thick incentral part of adult shell. Postumbonal partoccupies about 55-1>5% of total length of shell.
Umbo blunt; postero·dorsal margin nearlystraight. Two round·topped ridges run fromumbo to posterior margin. The upper one borders escutcheon. On the area between two ridges,a very shallow depression runs from umbo toposterior margin, corresponding with a ridge of
inner shell surface. Posterior margin of flat area
roundly and obliquely truncated. Prominenceand shape of concentric sculpture on shell surface varies specimen by specimen. Most of thespecimens have round· topped concentric ribs
numbering 5 to 6 in 1 mm distance on shell.
Some have acute·topped concentric ribs aroundumbo, and shallow and fine striations on marginal part of shell. Others have only irregularand obscure striations. The concentric ribs
obscure in escutcheon and area between tworidges. These varieties coexist at Locs. 17-1 and23-3. Tooth v-shaped.
Remarks:-These characteristics well agreewith SacceUa (Costanuculana) onoyamai (Otuka),804. Omma-Manganji Fauna in Gojome-Oga

reported from the Pliocene Nozaki Formationin the Noto Peninsula. This species is similar to
Nuculana fumosa E. A. Smith, 1895, from Bay
of Bengal, but the species is distinguishable fromN. fumosa by larger size of shell and weakersurface concentric ornamentation. This species
is somewhat similar to Saccella (Costanuculana)husamaru (Nomura, 1940) (UMUT RM16656,
PI. 31, figs. 14a, 14b), but S. husamaru has ahigher shell and a more pointed umbo which issituated in the center of shell length than thespecies.
The species was assigned to Nuculana by
Otuka (1935a, b). This is moved to Saccella(Costanuculana), because of its high and thickshell, and concentric ornamentation.
Locality: 7-1 (CM16430, CM16431); 17-1
(CM16432, CM16433, CM16434); 23-3 (CM16435).

227

Yoldia (Yoldia) kikuchii Kuroda, 1929, app. 10,
app. 6, figs. 10, 11; Uozumi, 1957, pI. 5, figs.
6a-c.
Yoldia (s. str.) kikuchii Kuroda. Oyama, 1951,
p. 149, pI. 6, figs. 5a-b.

Only one conjoined individual was collected.
It is subelliptical in outline, posteriorly narrowed, and compressed. The umbo is very low andsituated about the center of shell length. The
specimen can be identified with Yoldia (Y)kikuchii (Kuroda). Yoldia (Y.) laudabilis differsfrom the present species in having larger shelland a pair of weak lines running from the beakto the antero-ventral corner.
Locality: 41-2 (CM16440).
Yoldia (Cnesterium)johanni Dall, 1925

PI. 31, Fig. 16.
Yoldia (Cnesterium) johanni DaH, 1925, p. 32,

Portlandia hirosakiensis Iwai, 1959

PI. 31, Fig. 12.
Yoldia scapha Yokoyama. Yokoyama, 1926b,
p. 309, pI. 35, fig. 6.

Portlandia scapha hirosakiensis Iwai, 1959, pp.
53, 54, pI. 2, figs. 10-12.

Portlandia (Portland ella ) hirosakiensis Iwai. Ogasawara, 1977, p. 88, pI. 5, fig. 3.

Locality: 2-2c (CM16436); 12-2 (CM16437);
26-5d (CM16438).
Portlandia toyamaensis (Kuroda, 1929)

Pl. 31, Fig. 13.
Yoldia toyamaensis Kuroda, 1929, app. 11, app.
6, figs. 14, 15.

Portlandia (Portlandella) toyamaensis (Kuroda).
Uozumi, 1957, pI. 2, figs. 2, 2a-c.

Only one valve was collected. It is characterized by the inflated and high shell, and the umbo
situated about center of shell length.
Locality: Og2-1 (CM16439).

pI. 29, fig. 7; Habe and Ito, 1965, pp. 101,
102, pI. 33, fig. 6.
Yoldia johanni DaH. Kuroda, 1929, app. 12,
app. 7, fig. 16.

Shell subelliptical, postero-dorsal margin
slightly concave, which terminates a pointed
posterior end; fine striations obliquely crossing
growth lines. Yoldia (Cnesterium) johanni Dallis similar to Yoldia (Cnesterium) notabilis
Yokoyama, 1922. The postero-dorsal marginof notabilis is, however, more concaved thanthat of johanni. Y. (C.) scissurata Dall, 1898
and Y. (C.) ensifera Dall, 1897, which are alsosimilar to the species, have lower shell than thespecies.
Locality: 1-1 (CM16441); 2-1a (CM16442);
2-1b (CM16443); 2-3 (CM16444, CM16445);
4-1b (CM16446); 4-1c (CM16447); 4-1d (CM16448); 4-4 (CM16449); 4-5a (CM16450); 513b (CM16451); 20-1a (CM16452); 21-1 (CM16453); 23-2 (CM16454); 25-3-5 (CM16455).
Yoldia (Megayoldia) thraciaeformis(Storer, 1838)

Yoldia (Yoldia) kikuchii Kuroda, 1929

PI. 31, Fig. 17.

PI. 31, Fig. 15.

Yoldia thraciaeformis(Storer). Oldroyd, 1924,

Seiichiro MA TS UI

228

p. 27, pI. 5, fig. 1.
Yoldia scapha Yokoyama, 1926a, p. 247, pI. 31,
figs. 7 -11.
Portlandia (Megayoldia) thraciaeformis (Storer).
Uozumi, 1957, pp. 574-576, pI. 1, figs. 5,
5a, 7, 8, 8a, pI. 7, figs. 23, 28.
Yoldia (Megayoldia) thraciaeformis (Storer).
Habe and Ito, 1965, p. 102, pI. 33, fig. 7;
MacAlester in Moore, 1969, p. N241, fig. A9(10).
Locality: 2-2a (CM16456); 2-6 (CM16457,
CM16458); 2-7 (CM16459); 4-3 (CM16460);
4-4 (CM16461); 25-3-18 (CM16462); 25-3-41(CM16463); 26-5g (CM16464); 26-7c (CM16465).

Acharax tokunagai (Yokoyama, 1925)

PI. 31, Fig. 22.
Solemya tokunagai Yokoyama, 1925a, p. 31, pI.
6, figs. 1-3; Yokoyama, 1925b, p. 11, pI. 1,
figs. 20, 2I.
Solemya (Acharax) tokunagai Yokoyama. Kamada, 1962, pp. 37-39, pI. 1, figs. 1-3.
Acharax tokunagai (Yokoyama). Habe and Ito,
1965, p. 100, pI. 33, fig: I.
Locality: 41-2 (CM16466, CM16640).

Anadara amicula (Yokoyama, 1925)

PI. 32, Figs. 1, 2.
Arca amicula Yokoyama, 1925c, p. 19, pI. 7,
figs. 2-4.
Anadara amicula (Yokoyama). Takayasu, 1961,
pI. 1, figs. 13a-b; Kaseno and Matsuura,
1965, pI. 7, figs. 16, 17; Chinzei, 1973, pI.
14, fig. I.
Locality: 4-1b (CM16467); 4-1c (CM16468,
CM16469, CM16470); 4-1g (CM16471); 4-2a
(CM16472); 21-1 (CM16473); 25-1 (CM16474).

Limopsis tokaiensis Yokoyama, 1910

PI. 32, Figs. 4a, 4b.
Limopsis Tokaiensis Yokoyama, 1910, pp. 1, 2,
pI. 9, figs. 1-3, 5-7.
Limopsis Tokaiensis var. elongata Yokoyama,
1910, pp. 2, 3, pI. 9, fig. 4.

Limopsis tokaiensis Yokoyama. Kanno, 1962,
pI. 3, figs. 5a-b.
Locality: 5-lla (CM16475); 7-7a (CM16476);
7-8 (CM16477, CM16478).

Crenulilimopsis oblonga (A. Adams, 1860)

PI. 32, Figs. 6a, 6b, 7a, 7b.
Limopsis oblonga A. Adams, 1860, p. 412.
Limopsis crenata A. Adams, 1863b, p. 230;
Yokoyama, 1910, p. 3, pI. 9, figs. 8-11;
Yokoyama, 1920, pp. 173, 174, pI. 18, figs.
17, 18;Habe, 1961a, p.192, pI. 1, fig. 3.
Limopsis tumidula Thiele and Jaeckel, 1931, p.
186, pI. 6, fig. 26.
Pectunculina oblonga (A. Adams). Habe, 1953,
p. 204, pI. 29, figs. 12-14; Habe, 1961b, p.
112, p. 50, fig. 8.
Limopsis (Pectunculina) crenata A. Adams.
Kaseno and Matsuura, 1965, pI. 6, fig. 13;
Shikama and Masujima, 1969, pI. 7, figs. 10,
II.
Crenulilimopsis oblonga (A. Adams). Kuroda,
Habe and Oyama, 1971, pp. 339,340, pI. 71,
figs. 13-15.
Immature shell of the species has obliquely
subcircular outline, and mature shell becomes
postero-ventrally elongated. Surface is ornamented by fine ridge-like concentric ribs, which arecrossed by very fine radial furrows. Inner margin
is crenulated. The crenulation is obscure or often
disappears in anterior and posterior margins.
Locality: 20-1a (CM16483); 20-1b (CM16484, CM16485, CM16486).

Glycymeris derelicta (Yokoyama, 1928)

PI. 32, Figs. 8a, 8b.
Pectunculus derelictus Yokoyama, 1928, p. 361,
pI. 69, fig. I.
?Glycymeris nipponica (Yokoyama). Nomura
and Hatai, 1935, pp. 92,93, pI. 9, figs. 1013; Iwai, 1965, p. 26, pI. 14, figs. 15-17.
Glycymeris derelicta (Yokoyama). Nomura andZimbo, 1935, pp. 157, 158, pI. 15, figs. 1,2;
Chinzei, 1959, pp. 122, 123, pI. 11, figs. 1215.
?Glycy meris (s.s.) nipponica (Yokoyama). Hatai,
Masuda and Suzuki, 1961, pI. 1, figs. 7a-b.

804. Omma-Manganji Fauna in Gojome-Oga

The species has very characteristic features,
as noted by Chinzei (1959). It has unequilateraloutline, opisthogyral beak, and asymmetric,
duplivipcular ligament grooves. These features arerecognized either in adult and immature individuals. In specimens larger than about 25 mm high,the shell is ventrally or antero-ventrally elongated,
and the posterior adductor muscle scar is slightly
reduced. The immature individuals of the species
is very similar to Glycymeris rotunda and G.
nipponica in outline, but the latter two species
have nearly symmetric ligamental grooves.
Mature specimens of rotunda and nipponica
are postero-ventrally elongated, and neverreduce the posterior muscle scar.
Locality: 2-3 (CM16487); 4-4 (CM16488);
4-5g (CM16489): 23-2 (CM16490); 25-3-6(CM16491); 25-3-7.5 (CM16492); 25-3-33 (CM16493); 25-3-34 (CM16494); 25-3-52 (CM16495); 26-5g (CM16496).
Glycymeris yessoensis (Sowerby, 1889)

PI. 32, Figs. 9a, 9b.
Pectunculus yessoensis Sowerby, 1889, p. 570,

229

vestita or G. albolineata is found in a shallower
sandy bottom, and G. rotunda in a deeper
muddy bottom. In the Pliocene of the Kakegawa
area of the central Honshu, G. totomiensis or
G. nakamurai and G. rotunda represent a similar
pair of Glycymeris species (Chinzei, 1980).
Localiity: 4-1a (CM16497); 4-1b (CM16498);
4-1c (CM16499); 4-1d (CM16500); 6-1 (CM16501); 25-1 (CM16502).
Solamen spectabilis (A. Adams, 1862)

PI. 31, Fig. 18.
Crenella spectabilis A. Adams, 1862, p. 228.
Solamen spectabilis (A. Adams). Kuroda, Habe
and Oyama, 1971, p. 342, pI. 74, figs. 7, 8.

Locality: 21-1 (CM16503, CM16641).
Chlamys islandica (MUller, 1776)

PI. 31, Fig. 20.
Chlamys (s.s.) islandicus (MUller). Shikama andIkeya, 1964, pp. 29-54, pis. 1-2.

Chlamys islandicus (MUller). Habe and Ito, 1965,
p. 120, pI. 39, fig. 2.

pI. 28, fig. 19; Yokoyama, 1920, p. 168, pI.
18, figs. 1, 2; Yokoyama, 1922, p. 189, 190,
pI. 16, figs. 6,7.
Glycymeris yessoensis (Sowerby). Nomura andHatai, 1935, pp. 93-95, pI. 9, fig. 14.
Glycymeris (G~ycymeris) yessoensis (Sowerby).
Ogasawara, 1977, pp. 93-94, pI. 5, figs. 14,
15,18-22.

Chlamys islandica (MUller). Abbott, 1974, p.

This species is similar to Glycymeris derelicta
noted above. The fonner species, however, hasantero-posteriorly elongated, less inflated, thinner shell than derelicta. The outline and ligamental area of yessoensis is nearly symmetrical.
This species is restricted to the sandy bottom
Protothaca Association, while derelicta occurs
from the sandy silt facies as a common component of the Acila-Turritella Association. In
other words, yessoensis was living in a shallower
depth than derelicta. Similar congeneric species
pairs in the genus Glycymeris are found in theother areas. In the continental shelf of the
Pacific coast of southern Honshu, Glycymeris

Pecten tairanus Yokoyama, 1925b, pp. 8, 9, pI.

444, pI. 19, fig. 5147.

Locality: Og2-4 (CM16504).
Palliolum (Delectopecten) peckhami(Gabb, 1869)

PI. 31, Fig. 19.
1, figs. 8,9.

Palliolum(Delectopecten) peckhami (Gabb).
Weaver, 1942, pp. 96-97, pI. 11, fig. 6, pI.
21, fig. 4; Shuto, 1960, pp. 123, 124, pI. 12,
figs. 8,9.
Delectopecten peckhami (Gabb). Masuda, 1962,
pp. 158, 159, pI. 18, figs. 12-16.

Locality: Ogl-3 (CM16505); Ogl-5 (CM16506, CM16507).
Mizuhopectenpoculum (Yokoyama, 1926)

PI. 31, Fig. 21.

Seiichiro MATSUI

230

Pecten poculum Yokoyama, 1926a, pp. 245,
246, pI. 32, figs. 1-3.
Pecten kurosawaensis Yokoyama, 1926c, p.
388, pI. 45, fig. 3.
Patinopecten (Patinopecten) poculum (Yokoyama). Masuda, 1962, p. 209, pI. 24, fig. 1,
pI. 25, fig. 5.
Mizuhopecten poculum (Yokoyama). Iwai, 1965,
pp. 29, 30, pI. 15, figs. 11, 12.
Locality: 4-2b (CM16508); 6-1 (CM16509,
CM16510).
Lucinoma acutilineata (Conrad, 1849)
PI. 32, Fig. 10.
Lucina (Phacoides) borealis (Linne). Yokoyama,
1925a, p. 24, pI. 5, figs. 5-8; Yokoyama,
1925b, pp. 18, 19, pI. 1, fig. 2, pI. 3, figs. 1, 2.
Lucina acutilineata (Conrad). Weaver, 1942, pp.
143-144, pI. 34, figs. 8,11,16.
Lucinoma acutilineata (Conrad). Takayasu, 1961,
pI. 1, fig. 15.
Lucinoma acutilineatum (Conrad). Kamada,
1962, pp. 95-97, pI. 9, figs. 10-16, pI. 10,
figs. 1-3.
Locality: 2-1a (CM1651l); 5-12a (CM16512);7-6c (CM16513); 14-3 (CM16514); 20-1b (CM16515); 21-1 (CM16516); 23-1 (CM16517);
41-1 (CM16518).
Thyasira (Thyasira) tokunagai
Kuroda and Habe, 1951

Thyasira bisecta Conrad. Oldroyd, 1924, p. 120,
pI. 10, fig. 1; Yabe and Nomura, 1925, p. 84,
pI. 23, figs. 2,7-10; Yokoyama, 1926b, pp.
294, 295, pI. 35, figs. 2,3; Takayasu, 1961,
pI. 2, figs. 5, 6.
Thy as ira bisecta var. nipponica Yabe and Nomura, 1925, pp. 84-92, pI. 23, fig. 3, pI. 24, figs.
2-4.
Conchocele bisecta (Conrad). Habe, 1977, p.
129, pI. 24, fig. 19.
Locality: 7-6c (CM16521); 7-6g (CM16522);
14-1 (CM16523); 14-4d (CM16524); 14-5a(CM16525, CM16526); 15-3 (CM16527); 29-1
(CM16528); 41-1 (CM16529).
Axinopsida subquadrata (A. Adams, 1862)
PI. 33, Figs. la, 1b, 2a, 2b.
Cryptodon (Clausina) subquadratus A. Adams,
1862, p. 227.
Axinopsida subquadrata (A. Adams). Habe, 1955,
p. 10, pI. 1, figs. 8, 9.
Shell small, less than 4 mm high, subquadrate
in outline, inflated and thin. Some have a very
weak depression passing from beak to posteroventral corner. Antero-dorsal margin concave.
A node-like tooth just below beak in right valve.
The characteristics well coincide with Axinopsida subquadrata (A. Adams).
Locality: 4-1c (CM16530); 4-2a (CM16531,
CM16532); 4-2b (CM16533); 6-3 (CM16534).

PI. 32, Fig. 11.

Felaniella usta (Gould, 1861)

Thyasira gouldii (Philippi). Yabe and Nomura,
1925, p. 94, pI. 23, figs. 6a-b; Yokoyama,
1927a, p. 433, pI. 50, fig. 9; Yokoyama,
1927b,p. 457,pl. 52,figs. 3,4.
Thyasira tokunagai Kuroda and Habe, 1951,
p. 86; Habe, 1961b, p. 124, pI. 56, fig. 17;
Takayasu, 1962, pI. 1, fig. 2; Kaseno andMatsuura, 1965, pI. 13, fig. 2.
Thyasira (Thyasira) tokunagai Kuroda andHabe. Habe, 1977, p. 131, pI. 24, figs. 17, 18.

PI. 33, Fig. 3.

Locality: 2-1a (CM16519, CM16520).

Diplodonta usta (Gould). Yokoyama, 1920, pp.
130, 131, pI. 9, figs. 14-16; Yokoyama,
1922, p. 159, pI. 13, fig. 3.
Felaniella usta (Gould). Habe, 1955, p. 10, pI.
6, figs. 8, 9.
Locality: 4-1b (CM16535); 4-1c (CM16536);
4-1d (CM16642); 4-1e (CM16537, CM16538);
4-lf (CM16539); 4-1g (CM16540); 4-1h (CM16541).

Thyasira (Conchocele) bisecta (Conrad, 1849)

Cyclocardia aomoriensis (Chinzei, 1961)

PI. 32, Fig. 12.

PI. 33, Figs. 4a, 4b, 5.

804. Omma-Manganji Fauna in Gojome-Oga
Venericardia (Cyclocardia) aomoriensis Chinzei,
1961, p. 110, pI. 1, figs. 9-11.

The species is characterized by large andthick shell, nearly circular outline, and low andbroad ribs numbering 21 (Chinzei, 1961). Morethan ten abraded specimens examined here arerather small, less than 26 mm high, although the
holotype is 4 cm. The large specimens have thickand circular shell. Smaller ones not exceeding
20 mm high is somewhat variable in outline;
some are circular, and the others are trigonallysubcircular. The radial ribs are 19-23 in number.
Locality: 6-1 (CM16542, CM16543, CM
16544).

231

Locality: M3B (CM16552).
Tridonta borealis Schumacher, 1817

PI. 33, Figs. 9a, 9b.
Tridontaborealis Schumacher. Habe and Ito,
1965, p. 127, pI. 43, fig. 2.
Astarte(Tridonta) borealis (Schumacher).
Ogasawara, 1977, p. 105, pI. 11, figs. 8, 9,
13a-b.

Locality: 2-1b (CM16553); 2-2a (CM16554);
21-1 (CM16555); 25-3-51 (CM16556); Og2-1(CM16557, CM16558); Og2-4 (CM16559).
Clinocardium chikagawaense Kotaka, 1950

Cyclocardia ferruginea (Clessin, 1888)

PI. 33, Fig. 11.

PI. 33, Fig. 7.

Clinocardium chikagawaense Kotaka, 1950, pp.
46-49, pI. 5, figs. 1-6.

Venericardia ferruginea (Clessin). Chinzei, 1958,
pI. 7, fig. 6.
Cyclocardia ferruginea (Clessin). Habe and Ito,
1965, p. 128, pI. 43, fig. 9.

Cyclocardia sp.

Locality: 2-1a (CM16560); 2-2b (CM16561);
4-5a (CM16562); 4-5c (CM16563); 4-5e (CM16564); 4-5f (CM16565); 4-5g (CM16566);
4-5h (CM16567); 7-1 (CM16568); 20-1b (CM16569); 23-3 (CM16570); 25-3-1 (CM16571);
25-3-5 (CM16572); 25-3-35 (CM16573); 26-5e(CM16574).

PI. 33, Fig. 8.

Clinocardium fastosum (Yokoyama, 1927)

Three specimens examined here are smallin size, 5 mm high or lower. The shells are
similar to Venericardia (Cyclocardia) ferruginea
complexa Ogasawara (1977, pp. 107-109, pI.
11, figs. 3a-b, pI. 12, fig. 4) in outline, buthave only fifteen or sixteen radial ribs. Theinterspace of radial ribs is wider in these specimens than in complexa.
Locality: 4-5d (CM16549); 25-3-27 (CM16550); M4B (CM16551).

PI. 33, Figs. lOa, lOb.

Locality: 20-1b (CM16545, CM16546); 21-1
(CM16547); Og2-1 (CM16548).

Cardium fastosum Yokoyama, 1927c, pp. 178,
179, pI. 48, fig. 5.
Clinocardium fastosum (Yokoyama). Kaseno andMatsuura, 1965, pI. 13, fig. 11; Ogasawara,
1977, pp. 115, 116, pI. 11, figs. 16, 19.

Locality: 6-1 (CM16575); 24-1a (CM16576).
Fulvia mutica (Reeve, 1844)

PI. 33, Fig. 12.
Miodontiscus nakamurai (Yokoyama, 1923)

PI. 33, Fig. 6.
Venericardia nakamurai Yokoyama, 1923a, pp.
5,6, pI. 1, fig. 9.
Miodontiscus nakamurai (Yokoyama). Ogasawara,
1977, pp. 110, 111, pI. 10, figs. 3a-b, pI. 11,
figs. 1a-b, 2a-b.

Cardium muticum Reeve. Yokoyama, 1920, p.
128, pI. 9, figs. 11a-b; Yokoyama, 1922,
pp. 154, 155, pI. 12, fig. 7.
Fulvia mutica (Reeve). Habe and Ito, 1965, p.
133, pI. 44, figs. 7, 8; Habe, 1977, p. 174,
pI. 32, figs. 11, 12.

Locality: 4-1a (CM16577, CM16578).

Seiichiro MATSUI232

Macoma calcarea (Gmelin, 1791)

PI. 34, Fig. 2.
Macoma calcarea (Gmelin). Habe, 1955, p. 18,
pI. 1, figs. 14, 15; Chinzei, 1959, pp. 126128, pI. 11, fig. 11, text-fig. 3(1).

Locality: 2-3 (CM16579); 4-1a (CM16580);
4-1b (CM16581); 4-1h (CM16582); 4-2a (CM16583); 4-2b (CM16584); 4-2c (CM16585, CM
16586); 4-2d (CM16587); 4-3 (CM16588); 5-1a
(CM16589); 6-3 (CM16590); 7-6a (CM16591);
7-8 (CM16592); 7-9a (CM16593); 11-2 (CM16594); 12-1 (CM16595); 20-1b (CM16596);23-1 (CM16597); 25-3-1 (CM16598); 26-5e(CM16599); 26~7c (CM16600); 28-2 (CM16601);
Og2-4 (CM16602).

16.

Locality: 4-1g (CM16603); 4-2a (CM16604);
4-2b (CM16605); 5-1b (CM16606, CM16607);
5-lf (CM16608); 5-2j (CM16609); 24-1a (CM16610).
Dosinia (Phacosoma) japonica (Reeve, 1850)

PI. 34, Fig. 3.
Dosinia (Phacosoma) japonica (Reeve). Kira,
1959,p.141,pl.56,fig.7.
Phacosoma japonicum (Reeve). Habe, 1977,
p. 260, pI. 55, fig. 1.

Locality: 4-1e (CM16611).
Mercenaria stimpsoni (Gould, 1861)

PI. 36, Fig. 5.

Macoma tokyoensis Makiyama, 1927

PI. 34, Fig. 1.
Macoma dissimilis (Martens). Yokoyama, 1922,
p. 143, pI. 10, fig. 4.
Macoma tokyoensis Makiyama, 1927, p. 50;
Habe and Ito, 1965, p. 149. pI. 51, figs. 15,

Venus (Mercenaria) stimpsoni Gould. Yokoyama,
1922, p. 148, pI. 11, figs. 11, 12.
Mercenaria stimpsoni (Gould). Habe, 1955, p.
13, pI. 5, figs. 10, 11; Habe and Ito, 1965,
p. 137, 138, pI. 46, fig. 4; Chinzei, 1973, pI.
14, fig. 5.

Explanation of Plate 31
Fig.1. Nucula (Leionucula) niponica Smith, x2, Loc. 1-1 (CM16391).
Fig. 2. Acila (Acila) divaricata (Hinds), xl, Loc. Og2-4 (CM16394).
Fig. 3. Acila (Truncacila) nakazimai Otuka, xl, Loc. 1-1 (CM16396).
Fig. 4. Acila (Truncacila) sp., x5, Loc. 4-2a (CM16409).
Figs. 5,6. Nuculana sadoensis (Yokoyama), fig. 5, x3, Loc. 12-2 (CM16415); fig. 6, x 2.5, Loc.
Og2-1 (CM16417).
Fig. 7. Nuculana robai (Kuroda), x2, Loc. Og2-7 (CM16429).
Fig. 8. Nuculana yokoyamai KiJroda, x2, Loc. 2-2c (CM16419).
Figs. 9-11. Saccella (Costanuculana) onoyamai (Otuka), figs. 9, 10, x2, Loc. 17-1 (fig. 9: CM
16432, fig. 10: CM16433); fig. 11, x2, Loc. 7-1 (CM16430).
Fig. 12. Portlandia hirosakiensis Iwai, x2, Loc. 26-5d (CM16438).
Fig. 13. Portlandia toyamaensis (Kuroda), xl, Loc. Og2-1 (CM16439).
Figs. 14a, 14b. Saccella (Costanuculana) husamaru (Nomura), x2, off Jyogashima, Kanagawa
Prefecture, Central Japan, 100 m in depth (RM16656).
Fig. 15. Yoldia (Yoldia) kikuchii Kuroda, x1.5, Loc. 41-2 (CM16440).
Fig. 16. Yoldia (Cnesterium)johanni Dall, x2, Loc. 2-3 (CM16444).
Fig. 17. Yoldia (Megayoldia) thraciaeformis (Storer), xl, Loc. 2-6 (CM16457).
Fig. 18. Solamen spectabilis (A. Adams), x2, Loc. 21-1 (CM16503).
Fig. 19. Palliolum (Delectopecten)peckhami (Gabb), x1.5, Loc. Ogl-5 (CM16506).
Fig. 20. Chlamys islandica (MUller), xl, Loc. Og2-4 (CM16504).
Fig. 21. Mizuhopecten poculum (Yokoyama), x1/2, Loc. 6-1 (CM16509).
Fig. 22. Acharax tokunagai (Yokoyama), xl, Loc. 41-2 (CM16466).

MA TS UI: Omma-Manganji Fauna in Gojome-Oga

Plate 3 1

804. Omma-Manganji Fauna in Gojome-Oga

Locality: 4-1a (CM16612); 4-1c (CM16613).
Protothaca (Protocallithaca) adamsi(Reeve, 1863)

have angular postero-ventral corner.
Locality: 14·1 (CM16630); 26-4 (CM16631);
26-5g (CM16632); M10B (CM16633).

PI. 34, Fig. 4.

Myadora japonica Habe, 1950

Venus rigida Gould. Yokoyama, 1927a, p. 430,

PI. 34, Fig. 7.

pI. 50, figs. 3, 4.
Protocallithaca adamsi (Reeve). Nomura, 1937,

p. 10, pI. 3, figs. 4a-b.
Gallithaca (Protocallithaca) adamsi (Reeve). Habe,

233

Myadora japonica Habe, 1950, p. 27, pI. 4, figs.

4-6.
Locality: 21-1 (CM16634, CM16635).

1955, p. 14, pI. 5, figs. 1, 2.
Protothaca (Gallithaca) adamsi (Reeve). Chinzei,

1961, p. 117,118, pI. 1, fig. 8.
Locality: 4-1c (CM16614); 4-1e (CM16615);
4·lf (CM16616).
Mya (Mya) cuneiformis (B6hm, 1915)

PI. 34, Figs. 6a, 6b.
cuneiformis (Bohm). Fujie, 1957, pp.
395-397, pI. 3, fig. 5, pI. 4, figs. 1-6; Chinzei, 1973, pI. 14, fig. 15.
Mya (Arenomya) cuneiformis (Bohm). Kamada,
1962, pp. 141, 142, pI. 16, figs. 14-16.
Mya (Mya) cuneiformis (B6hm). MacNeil, 1965,
pp. G35-G37, pI. 7, figs. 2, 3, 5-8, 12, 15;
Honda, 1978, pI. 1, figs. 14a, 14b,15.
Mya

Locality: 4-2c (CM16617); 4-3 (CM16618);
4-4 (CM16619); 4·5b (CM16620); 4-5c (CM16621); 4·5d (CM16622); 4·5e (CM16623);
4-5g (CM16624); 20-1a (CM16625); 20-1b(CM16626); 23-2 (CM16627); 24-4d (CM16628);
26·5g (CM16629). .

Periplomaplane Ozaki, 1958

PI. 34, Fig. 9.
Periploma plane Ozaki, 1958, p. 120, pI. 18,

figs. 3, 4.
This species is closely allied to Periploma otohimeae Habe, 1952 nomen nudum (= P. ovata
Kuroda and Horikoshi, 1952 non d'Orbigny,
1846; = P. plane Ozaki sensu Habe, 1977),
but has longer shell than the latter. The postumbonal part of plane forms about 56% (pI. 18,
fig. 3 of Ozaki, 1958) - 59% (a conjoined
specimen from Loc. 4-4) of the shell length,
while otohimeae forms about 44% (pI. 103,
fig. 2 of Kuroda, Habe and Oyama, 1971). The
posterior of this species is angular, while one ofotohimeae is rather rounded.
Locality: 4-4 (CM16636).
Periploma cf. besshoensis (Yokoyama, 1924)

PI. 34, Fig. 8.
cf. Tellina besshoensis Yokoyama, 1924, p. 14,

Pandora (Pandorella) wardiana A. Adams, 1859

PI. 34, Figs. 10, 11.
Pandora (Kennerlia) wardiana A. Adams. Habe,

1952, pp. 123, 124, pI. 18, figs. 1-3; Hatai,
Masuda and Suzuki, 1961, pI. 2, figs. 13a-b.
The specimens is referable to Pandora wardiana
A. Adams in having nearly straight posterodorsal margin and a fold running from beak toantero·ventral margin. Pandora pulchellus has
concave postero-dorsal margin and. more compressed shell than the species. Pandora pseudobilirata and P. otukai also have the fold, but

pI. 2, figs. 1-5.
Four conjoined and deformed specimens are
examined. They are similar to Periploma besshoensis in their large size (about 60 mm long orless) and oval outline. They, however, have lower
shell than typical besshoensis, and seem not torostrate posteriorly. The shell torsion, which ischaracteristic feature of the species, can not be
assessed in the specimens, because of deformation of the shells.
Locality: 41-2 (CM16637, CM16638).
Thracia kakumana (Yokoyama, 1927)

234

Seiichiro MATSUI

PI. 34, Fig. 12.
Tel/ina kakumana Yokoyama, 1927c, pp. 177,
178, pI. 47, fig. 14.
Thracia kakumana (Yokoyama). Habe, 1955,
p. 26, pI. 1, figs. 3,4; Itoigawa, 1958, pl. 2,
fig. 4; Ogasawara, 1977, p. 102, pI. 17, figs.
8,13.

Locality: 5-1h (CM16639).
Acknowledgments
I am especially indebted to Emeritus Professor
Tetsuro Hanai of the University of Tokyo foradvice and encouragement. I would also like tothank Drs. Kiyotaka Chinzei and Itaru Hayami
of the University of Tokyo, Dr. Yasuhide Iwasaki
of Kumamoto University, Dr. Tomowo Ozawaof Hyogo University of Education, Dr. Toshiyuki
Yamaguchi of Chiba University, Dr. Hiroshi
Kitazato of Shizuoka University, Dr. Tadashige
Habe of Tokai University and Dr. Takashi
Okutani of Tokyo University of Fisheries forhelpful suggestions and discussions. The manu·
script was critically read by Dr. Chinzei. His
suggestions and constructive criticism are acknowledged.
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Explanation of Plate 32
Figs. 1, 2. Anadara amicula (Yokoyama), xl, Loc. 4-1c (fig. 1: CM16468, fig. 2: CM16469).
Figs. 3a, 3b. Limopsis sp. A, x3, Loc. 26-7c (CM16479).
Figs. 4a, 4b. Limopsis tokaiensis Yokoyama, x2, Loc. 7-8 (CM16477).
Figs. 5a, 5b. Limopsis sp. B, x2, Loc. Og2-4 (CM16481).
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Fig. 11. Thyasira (Thyasira) tokunagai Kuroda and Habe, x3, Loc. 2-1a (CM16519).
Fig. 12. Thyasira (Conchocele) bisecta (Conrad), x1/2, Loc. 14-5a (CM16525).

MA TSUI: Omma-Manganji Fauna in Gojome-Oga

Plate 32

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12, pp. 579-592.

Kira, T. (1959): Coloured illustrations of theshells of Japan, vol. 1, enlarged and revised
edition. 240 pp., 81 pIs. Hoikusha Publ.
Co., Ltd., Osaka.
Kitazato, H. (1975): Geology and geochronologyof the younger Cenozoic of Oga Peninsula.
Tohoku Univ. Inst. Geol. Pal. Contr., no. 75,
pp. 17-49 (in Japanese with English abstract).
Kosuge, S. (1972): Illustrations of type specimens of molluscs described by William
Healey Dall (North Western Pacific gastropods). 29 pIs., Otsuka Kogei Sha.
Kotaka, T. (1950): A new Clinocardium from
Aomori Prefecture. Short Pap. Inst. Geol.
Palaeont. Tohoku Univ., no. 2, pp. 46-50,
pI. 5.
(1959): The Cenozoic Turritellidae of Japan.
Sci. Rep. Tohoku Univ., 2nd Ser., vol. 31,
no. 2, pp. 1-135, pIs. 1-15.
Kuroda, T. (1929-1935): An illustrated catalogue of the Japanese shells. Venus, vol.
1-5, appendix, pp. 1-154 (in Japanese).
(1934): On some rare shells from Sagami
Bay collected by His Majesty, the Empireof Japan. Ibid., voL 4, no. 4, pp. 204-208.
-and Habe, T. (1951): Nomenclatural notes.
I/Iust. Cat. Japan. Shells, no. 13, p. 86.
- , - - and Oyama, K. (1971): The sea
shells of Sagami Bay. 741 pp. (in Japanese),
489 pp. (in English), 121 pIs., Maruzen Co.,
Ltd., Tokyo.
MacNeil, F. S. (1965): Evolution and distributionof the genus Mya, and Tertiary migrations of
Mollusca. U.S. G. S. Prof. Paper, 483-G, pp.
Gl-G51, pIs. 1-11.

Explanation of Plate 33
Figs. la, 1b, 2a. 2b. Axinopsida subquadrata (A. Adams), x10, figs. la, 1b, Loc. 4-2a (CM16531);
figs. 2a, 2b, Loc. 6-3 (CM16534).
Fig. 3. Felaniella usta (Gould), x2, Loc. 4-1e (CM16537).
Figs_ 4a, 4b, 5. Cye/ocardia aomoriensis (Chinzei), xl, figs. 4a, 4b, Loc. 6-1 (CM16542); fig. 5,
Loc. 6-1 (CM16543).
Fig. 6_ Miodontiscus nakamurai (Yokoyama), x4, Loc. M3B (CM16552).
Fig. 7. Cyclocardia ferruginea (Clessin), x4, Loc. 20-1b (CM16545).
Fig. 8 .. Cye/ocardia sp., x4, Loc. M4B (CM16551).
Figs. 9a, 9b. Tridonta borealis Schumacher, xl, Loc. 25·3-51 (CM16556).
~igs. lOa, lOb. Clinocardium fastosum (Yokoyama), xl, Loc. 24-1a (CM16576).
Fig. 11. Clinocardium chikagawaense Kotaka, xl, Loc. 7-1 (CM16568).
Fig. 12. Fulvia mutica (Reeve), xl, Loc. 4-1a (CM16577).

MA TSUI: Omma-Manganji Fauna in Gojome-Oga

Plate 33

804. Omma-Manganji Fauna in Gojome-Oga
Maiya, S., Saito, T. and Sato, T. (1976): Late
Cenozoic planktonic foraminiferal biostratigraphy of northwest Pacific sedimentary
sequences. Progress in Micropaleontology,
pp. 395-422, pis. 1-6.
Makiyama, J. (1927): Molluscan fauna of thelower part of the Kakegawa Series in theprovince of Totomi, Japan. Mem. Coll. Sci.
Kyoto Imp. Uniu., Ser. B, vol. 3, no. 1, pp.
1-147, pis. 1-6.
--(1940): Nomenclatural notes on some
genera of Turridae. Jour. Geol. Soc. Japan,
vol. 47, no. 558, pp. 133-134 (in Japanesewith English abstract).
Marincovich, L. Jr. (1977): Cenozoic Naticidae(Mollusca: Gastropoda) of the Nortq.eastern
Pacific. Bull. Amer. Paleont., vol. 70, no.
294, pp. 169-494, pis. 17-42.
Masuda, K. (1962): Tertiary Pectinidae of Japan.
Sci. Rep. Tohoku Univ., 2nd Ser., vol. 33,
no. 2, pp. 117-238, pis. 18-27.
Matsui, S. (1977): Geology and paleontology of
the Taihei area, Akita Prefecture. 34 p.
(Graduation thesis, Tokyo Univ., MS).
-(1979): Geology and paleontology of theupper Cenozoic strata in the environs of
Akita City. 134 pp. (Master thesis, Ibid.,MS).
(1981): Stratigraphy of the upper Cenozoic
marine strata in the Akita-Gojome area andits relation to those of the Oga Peninsula.
Jour. Geol. Soc. Japan, vol. 87, no. 1, pp.
1-16 (in Japanese with English abstract).
Mitsunashi, T. et al. (1963): Southern part of
Gojome. Geological map of the oil and gas
field of Japan, no. 5, Geol. Surv. Japan.
Moore, R.C. (ed.) (1969): Treatise on invertebrate paleontology part N., vol. 1,489 pp.
Geol. Soc. Amer. and Univ. Kansas.
Nakamura, R. and Matoba, Y. (1978): Paleomagnetic chronology of Tentokuji andSasaoka Formations in Akita Oil Field(abstract). Rep. Tohoku Branch, Geol.
Soc. Japan, no. 8, pp. 11-13 (in Japanese).
Nomura, S. (1937): On some Recent veneridmollusks from northeast Honshu, Japan.
Saito Ho-on Kai Mus. Res. Bull., no. 13,
pp.7-10.
and Hatai, K. (1935): Pliocene Mollusca
from the Daishaka shell-beds in the vicinityof Daishaka, Aomori-ken, northern Hosnhu,
Japan. Ibid., no. 6, pp. 83-142, pis. 9-13.
-and Zinbo, N. (1935): Mollusca from the237

Yanagawa shell-beds in the Hukushima
Basin, northeast Honshu, Japan. Ibid.,no. 6, pp. 151-192, pI. 15.
Ogasawara, K. (1977): Paleontological analysisof Om rna Fauna from Toyama-Ishikawa
area, Hokuriku Province, Japan. Sci. Rep.
Tohoku Univ.; 2nd Ser., vol. 47, no. 2, pp.
43-156, pis. 3-22.
Okutani, T. (1964): Report on the archibenthal
and abyssal gastropod Mollusca mainlycollected from Sagami Bay and adjacentwaters by the R.V. Soyo-Maru during theyears 1955-1963. Jour. Fac. Sci. Univ.
Tokyo, Sec. 2, vol. 15, pt. 3, pp. 371-447,
pis. 1-7.
Oldroyd,!. S. (1924): The marine shells of theWest Coast of North America, Stanford
Uniu. Publ., Univ. Ser., Geol. Sci., vol. 1,
no. 1, pp. 1-247, pis. 1-57.
-(1927): The Marine shells of the West
Coast of North America, pts. 1--3, Ibid.,
vol. 2, pts. 1-3, pp. 1'--941, pis. 1-108.
Otuka, Y. (1935a): Stratigraphy of the northeastern part of the Oti Graben, Ishikawa
Prefecture. Jour. Geol. Soc. Japan, vol. 42,
no. 503, pp. 483-510, pI. 14 (in Japanese).
(1935b): The Oti Graben in southern Noto
Peninsula, Japan, part 3. Bull. Earthquake
Res. Inst., vol. 8, pt. 4, pp. 846-909, pis.
53-57.
--(1936): Pliocene molluscan from Manganzi
in Kotomo-mura, Akita Prefecture, Japan.
Jour. Geol. Soc. Japan, vol. 43, no. 516, pp.
726-736, pis. 40, 41.
- - (1939): Mollusca from the Cenozoic Systemof eastern Aomori Prefecture, Japan. Ibid.,
vol. 44, no. 544, pp. 23-31, pI. 2.
Oyama, K. (1951): A preliminary taxonomy of
the Neogene Taxodonta of Japan. Miner.
Geol., vol. 4, no. 6, pp. 146-156, pI. 6 (inJapanese).
Ozaki, H. (1958): Stratigraphical and paleontological studies on the Neogene andPleistocene Formations of the Tyosi district.
Bull. Nat. Sci. Mus., vol. 4, no. 1, pp. 1182, pis. 1-24.
Powell, A. W. B. (1969): The Family Turridae
in the Indo-Pacific. Indo-Pacific Mollusca,
vol. 2, no. 2, pp. 207-416.
Sakagami, S. et al. (1966): Fossils from theTomikawa Formation of Kamiiso, Oshima
Peninsula, Hokkaido 1. Mollusca. Bull.

238

Seiichiro MATSUI

Rokkaido Uniu. Educ., Sec. 2B, vol. 17,
no. 1, pp. 78-93, pIs. 1-4 (in Japanese).
Sanders, H. L. (1958): Benthic studies in
Buzzards Bay. 1. Animal sediment relationships. Limnol. Oceanogr., vol. 3, no. 3, pp.
245-258.
Sawada, Y. (1962): The geology and paleontology of the Setana and Kuromatsunai
area in southern Hokkaido, Japan. Mem.
Muroran Inst. Tech., vol. 4, no. 1, pp. 1103, pIs. 1-8.
Schenck, H. G. (1936): Nuculid bivalves of theGenus Acila. Geol. Soc. Amer. Spec. Pap.,
no. 4, pp. 1-149, pIs. 1-18.
Scott, R. W. (1974): Bay and shoreface benthic
communities in the Lower Creatceous.
Lethaia, vol. 7, pp. 315-330.
Shikama, T. and Ikeya, N: (1964): On thevariation of Chlamys islandicus from a partof Set ana Formation. Sci. Rep. YokohamaNat. Uniu., Sec. 2, no. 11, pp. 29-54, pIs.
1-2.
--and Masujima, A. (1969): Quantitative
studies of the molluscan assemblages in the
Ikego-Nojima Formations. Ibid., no. 15,
pp. 61-94, pIs. 5-7.
Shuto, T. (1960): On some pectin ids and venerids
from the Miyazaki Group (Paleontologicalstudy of the Miyazaki Group-VIII). Mem.
Fac. Sci. Kyushu Uniu., Ser. D, vol. 9, no.
3, pp. 119-149, pIs. 12-14.
--(1964): Naticid gastropods from the Miyazaki Group (Paleontological study of the
Miyazaki Group-X). Trans. Proc. Palaeont.
Soc. Japan, n.s., no. 55, pp. 281-293,

pIs. 42, 43.
Smith, E. A. (1875): A list of Gastropoda
collected in Japanese seas by Commander
H. C. St. John, R. N. Ann. Mag. Nat. Rist.,
4th Ser., vol. 15, pp. 414-427.
--(1885): Report on the Lamellibranchiata.
Challenger Rep., vol. 13, pp. 1-341. pIs.
1-25.
Sowerby, G. B. (1889): Descriptions of fourteen
new species of shells from China, Japan and
the Andaman Islands, chiefly collected by
Depty Surgeon General R. Hungerford. Proc.
Zool. Soc. London, for the year 1888, pp.
565-570, pI. 28.
- - (1914): New Mollusca of the genus Pleurotoma (Surcura), Oliua and Limopsis fromJapan. Ann. Mag. Nat. Rist., Ser. 8, vol. 13,
p. 445, pI. 18.
Stanley, S. M. (1970): Relation of shell form tolife habits in the Bivalvia (Mollusca). Geol.
Soc. Amer. Memoir, no. 125, pp. 1-296,
pIs. 1-40.
Suzuki, K. and Kanehara, K. (1936): On threeforms of Nuculana from the Pliocene ofJapan. Jour. Geol. Soc. Japan, vol. 43, no.
510, pp. 177-185, pI. 10.
Takayasu, T. (1961): On stratigraphy and fossil
fauna in the environ of Tofuiwa, northernpart of Akita City, Akita Prefecture. Rep.
Res. Inst. Undergr. Resour. Min. Coli., Akita
Uniu., no. 25, pp. 1-14, pIs. 1-3 (in Japanese with English abstract).
-(1962): On the fossil faunas from the
Kitaura and Wakimoto formations, Oga
Peninsula, Akita Prefecture. Ibid., no. 27,

Explanation of Plate 34
Fig.1. Macoma tokyoensis Makiyama, xl, Loc. 5-1b (CM16606).
Fig. 2. Macoma calcarea (Gmelin), xl, Loc. 4-2c (CM16585).
Fig. 3. Dosinia (Phacosoma)japonica (Reeve), xl, Loc. 4-1e (CM16611).
Fig. 4. Protothaca (Protocallithaca) adamsi (Reeve), xl, Loc. 4-lf (CM16616).
Fig. 5. Mercenaria stimpsoni (Gould), xl, Loc. 4-1a (CM16612).
Figs. 6a, 6b. Mya (Mya) cuneiformis (Bohm), x1/2, Loc. 4-2c (CM16617).
Fig. 7. Myadorajaponica Habe, x3, Loc. 21-1 (CM16634).
Fig. 8. Periploma cf. besshoensis (Yokoyama), xl, Loc. 41-2 (CM16637).
Fig. 9. Periplomaplane Ozaki, xl, Loc. 4-4 (CM16636).
Figs. 10, 11. Pandora (Pandorella) wardiana A. Adams, xl, fig. 10, Loc. 14-1 (CM16630); fig. 11,
Loc. M10B (CM16633).
Fig. 12. Thracia kakumana (Yokoyama), x1/2, Loc. 5-1h (CM16639).

MA TSU/: Omma-Manganji Fauna in Gojome-Oga

Plate 34

804. Omma-Manganji Fauna in Gojome-Oga

pp. 43-47, pI. 1 (in Japanese).
Thiele, J. and Jaeckel, S. (1931): Muscheln der
Deutschen Tiefsee-Expedition. Deutsche
Tiefsee-Expedition 1898-1899, vol. 21,
Heft. 1, pp. 159-268, pis. 1-10.
Tiba, R. (1969): New species of the Genus
Clinopegma, C. borealis, n. sp. (Buccinidae).
Venus, vol. 28, no. 3, pp. 135-136, pI. 7.
-and Kosuge, S. (1980): Volutomitridae H.
and A. Adams. North Pacific Shells, no. 3,
pp. 1-5 (in Japanese).
and - - (1982): Genus Clinopegma Grant
and Gale. North Pacific Shells, no. 12, pp.
1-50_
Uozumi, S. (1957): Studies on the molluscan
fossils from Hokkaido, Part 2, Genera
Yoldia and Portlandia. Jour. Fac. Sci.
Hokkaido Univ., Ser. 4, vol. 9, no. 4, pp.
539-596, pis. 1-7.
Weaver, C. E. (1942): Paleontology of the marine
Tertiary formations of Oregon and Washington. Univ. Washington Publ. Geol., vol. 5,
pp. 1-789, pis. 1-104.
Yabe, H. and Nomura, S. (1925): Notes on the
Recent and Tertiary species of Thyasirafrom Japan. Sci. Rep. Tohoku Imp. Univ.,
2nd Ser., vol. 7, no. 4, pp. 83-95, pis. 2324.
Yokoyama, M. (1910): On species of Limopsis
found in the Neogene of Koshiba. Jour.
Geol. Soc. Tokyo, vol. 17, no. 205, pp.
1-5, pI. 9.
(1920): Fossils from the Miura Peninsula
and its immediates north. Jour. Coli. Sci.
Imp. Univ. Tokyo, vol. 39, art. 6, pp. 1193, pis. 1-19.
-(1922): Fossils from the Upper Musashinoof Kazusa and Shimosa. Ibid., vol. 44,
art. I, pp. 1-200, pis. 1-17.

-

239(1923a): On some fossil shells from theIsland of Saishu in the Strait of Tsushima.
Ibid., vol. 44, art. 7, pp. 1-9, pI. l.
-(1923b): Tertiary Mollusca from Dainichiin Totomi. Ibid., vol. 45, art. 2, pp. 1-18,
pis. 1-2.
(1924): Molluscan remains from the lowest
part of the J6-Ban Coal-Field. Ibid., vol. 45,
art. 3, pp. 2-22, pis. 1-5.
-(1925a): Molluscan remains from the uppermost part of the J6-Ban Coal-Field. Ibid.,
vol. 45, art. 5, pp. 1-34, pis. 1-6.
(1925b): Molluscan remains from the
middle part of the J6-Ban Coal-Field.
Ibid., vol. 45, art. 7, pp. 1-23, pis. 1-3.
-(1925c): Tertiary Mollusca from Shinanoand Echigo. Jour. Fac. Sci. Imp. Univ.
Tokyo, Sec. 2, vol. I, pt. 1, pp. 1-23, pis.
1-7.
-(1926a): Tertiary Mollusca from the oilfield of Embets and Etaibets. Ibid., vol. 1,
pt. 7, pp. 235-248, pis. 30-32.
-(1926b): Fossil shells from Sado. Ibid.,
vol. 1, pt. 8, pp. 249-312, pis. 32-37.
-(1926c): Fossil Mollusca from the OilField of Akita. Ibid., vol. 1, pt. 9, pp. 377389, pis. 44-45.
-(1927a): Mollusca from the upper Musashino of Tokyo and its suburbs. Ibid., vol.
1, pt. 10, pp. 391-437, pis. 56-60.
- (1927b): Mollusca from the upper Musashino of western Shimosa and southernMusashino. Ibid., vol. 1, pt. 10, pp. 439457, pis. 51, 52.
-(1927c): Fossil Mollusca form Kaga. Ibid.,
vol. 2, pt. 4, pp. 165-182, pis. 47-49.
-(1928): Neogene shells from the Oil-fieldof Higashiyama, "Echigo. Ibid., vol. 2, pt. 7,
pp. 351-362, pis. 68-69.

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 140, pp. 240-262, pis. 35-40, December 30, 1985

805. CYST AND THECATE FORMS OF PYROPHACUS STEINII (SCHILLER)
WALL ET DALE, 1971 *KAZUMI MATSUOKA
Department of Geology, Faculty of Liberal Arts, Nagasaki University,
Nagasaki 852, Japan

Abstract. The cyst form of Pyrophacus steinii (Schiller) Wall et Dale is clari·fied as a result of both field and laboratory observations. Thecate forms germinatedfrom living cysts identified as Tuberculodinium vancampoae (Rossignol) Wall are
assignable to Pyrophacus steinii on the basis of detailed observation of their plate
distribution. Furthermore, many thecate specimens of P. steinii including living
cysts identical with T. vancampoae were found in the summer plankton of Omura
Bay.
According to these data, T. vancampoae is regarded as a resting cyst of not
only P. vancampoae (Rossignol) but also P. steinii, and P. vancampoae is concluded
to be a subspecies of P. steinii.

But the correlative thecate form of this cyst
species have never been fixed until the present,
because the plate formula (plate distribution
pattern) which is the most important characterfor the thecate dinoflagellates is extremely
variable in number and shape and is not usefulin case of its parent thecate genus Pyrophacus.
On the contrary, recent studies of modem
dinoflagellate cysts reveal that the cyst morphotype (=cyst species) probably appear to be anatural species (Wall and Dale, 1968).
The present paper documents that the -realtaxonomic position of the thecate form of
T. vancampoae is confirmed on the basis of
the modem biological methodology and thepaleontological account to be cyst form. And
through the consideration about this species,
the taxonomical significance in both modem
and fossil dinoflagellate cysts will be clarified.

Introduciton
Tuberculodinium vancampoae (Rossignol) Wall
1967 has a lenticular body and a hypocystal
archeopyle. Owing to these characteristic fea·tures, this species is easily distinguishable fromother fossil dinoflagellate cysts.
T. vancampoae is also regarded as an usefulindicator of the tropical to warm temperateenvironment based on the modem distribution
in the Atlantic (Wall and Dale, 1971; Harland,1982) and in the Pacific (Matsuoka, 1985). In
Japan, this species has been reported from the
middle Miocene to Early Pleistocene sedimentsin the Niigata area (Matsuoka, 1983) and in the
Kinki area (Harada, 1984; Matsuoka, 1976).
These two evidences suggest that T. vancampoae
has a possibility to be an useful fossil as a tropi.
cal to warm temperate marine environment
since the Neogene in Japan.

Historical review of study of
Pyrophacus and Tuberculodinium*Received November 7,1984, revised manuscript
received August 9, 1985: Read October 17,
1982 at Mie University.

The genus Pyrophacus was first established240

805. Cyst and Theca of Pyrophacus steinii

241

Genus Pyrophacus Stein
STEIN (1883)

SCHILLER (1935)

I Pyrophacus hor%gicum Stein

~

----

hor%gium I
IPyrophacus hor%gicum Stein I Pyrophacus
steinii Schiller
Pterospermopsis? Van Campoae

ROSSIGNOL (1962)

STEIDINGER & DAVIS(1967)

Rossignol

IPyrophacus hor%gicum Stein I Pyrophacus hor%gicurn I LPyrophacus Form B, I
steinii Schillerl

WALL (1967)

WALL & DALE (1971)

Tubercu/odinium uancampoae

IPyrophacus hor%gium Stein I

Pyrophacus steinii (Schiller)
Wall et Dale

BALECH (1979)I

I Pyrophacus hor%gium Stein I(Rossignol) WallI I ----/

I

Pyrophacus uancampoae (Rossignol)
Wall et Dale

..

I

I

Pyrophacus steinii subsp .
Pyrophacus steinii subsp .
steinii (Schiller)
Wall et Daleuancampoae (Rossignol) Wall .t Dale-------________________.. __ J :________________________________
Pyrophacus steinii (Schiller) Wall et Dale

Text-fig. 1.

Taxonomic history of the genus Pyrophacus.

by Stein (1883) and at that time this genus
contained only one species, P. horologium
Stein. Schiller (1935) recognized one species
and one variety, P. horologicum Schiller and
P. horologicum var. steinii Schiller based on
difference of thecal plate formula in the genus.
Apart from plankton research, Rossignol(1962) found a peculiar fossil species from the. Pleistocene sediments and named it Pterospermopsis ? van campoae. Later, Wall (1967) also
obtained this species from deep sea core samplesof the Caribbian Sea and erected the new cyst
genus Tuberculodinium with emendation of
P. vancampoae.
Steidinger and Davis (1967) noticed thepresence of a characteristic form consisting of
more plates than other varieties of P. horologicum and called this form P. Form B I.
Wall and Dale (1971) carried out an incubation experiment of several cyst forms of thegenus Pyrophacus and reexamined the classification of this genus. They concluded that Tuberculodinium vancampoae (Rossignol) is a cyst

form of living P. Form BI of Steidinger andDavis, and as a result, they recognized thefollowing three Pyrophacus species; P. horologium Stein, P. steinii (Schiller) Wall et Dale
and P. vancampoae (Rossignol) Wall et Dale.
But they did not find a cyst form for P. steinii(Schiller) Wall et Dale.
Recently, Balech (1979) reexamined theplate morphology of the genus Pyrophacus
and recognized two species and one subspecies.
He concluded that P. vancampoae (Rossignol)
Wall et Dale is a subspecies of P. steinii (Schiller)
because the difference in plate distribution between these two is rather than minor.
The taxonomic history of these species,
subspecies, and varieties is shown in Text-fig. 1.
Materials and method
Samples containing various dinoflagellate
cysts were collected in gravity cores from Omura
Bay (Lat. 32°53'N, Long. 129°54'E, water
depth -18 m), Nagasaki Prefecture, west Japan

Kazumi MATSUOKA242

on 12 March, 1981. This bay is influenced by
the warm Tushima Current, and its surface watertemperature and chlorinity are as follows;
9 ± 2°C in winter, 30 ± 2°C in summer and17.5-19% 0 (Nagasaki Univ., 1976). The sediments are black and saplopelic mud sometimes
containing small shell fragments.
Until the start of the incubation experiment,
the samples were stored in the refrigerator for
three to four months. The upper 2 cm of thecore was provided for the investigation. Before
incubation, the material (about 1.9 ml) was
cleaned by sonification and sieved between
125 p.m and either 37 p.m or 20 p.m stainlesssteel screen. The materials retained on the latter
screens was washed in filtered sea water passed

several times through a Whatman GF/C glass
filter.
The isolated cysts picked up by a capillary
pipet were placed in a culture dish containingca. 1 ml filtered sea water. The incubation was
carried out under the following condition; temperature 2Q-22°C, fluorescent light about
4,000 lux, light-dark cycle 14-10 hours.
For small thecate forms described in detaillater, a vegetative newly formed cell was individually placed into another chamber. This
operation was repeated until the appearance ofthe small thecate forms. The materials remaining
after the incubation experiment was used for theinvestigation of cyst morphology. For palynological analysis, the usual procedure (Matsu-

12111 4p 2ap 3" 11

13 '11 2p 6 1111

14' II 4p 6 1111

12111 7p 3 1111

Text-fig. 2. Hypothecallabeling systems of several authors and proposal of a new system.
Abbreviation in Wall and Dale (1971) ... r.v.; right ventral, 1.1.; left lateral, r.l.; right lateral, d.; dorsalintercalary plate.

805. Cyst and Theca of Pyrophacus steinii

oka, 1985) was adopted.
Many vegetative cells included in surface
plankton were also provided for the present
study for taking the information of the plate
formula in situ. These samples were collectedfrom the surface water of Omura Bay (Lat.
32°54'N, Long. 129°52'E) in June of 1983and July of 1984 by net haul. At that time,
the surface temperature was 20°C and 33.5 % 0
in salinity.
Labeling on the antapiral plates of thegenus Pyrophacus Difference of labeling among several authors
Since Stein (1883) first described the genus
Pyrophacus, the plate formula of this genus has
not been fixed, because it has considerable variation in plate number. In the description of
Pyrophacus Form B1 , Steidinger and Davis(1967) noticed that a large and nearly triangularplate is always present just below the sulcus, andnamed it coupling antapical plate (C.A.P.) (Textfig. 2). Wall and Dale (1971) proposed a newlabeling system and later Balech (1979) suggested
another one. But there are major differences
between these two in the antapical series (Textfig. 2). According to Wall and Dale (1971),
the distinctive and larger triangular plate which
always contacts the small elliptical posterior
sulcal platelet is the first antapical plate (1" "),the plate which constantly occupies the left
position of the 1" " plate is the second antapicalplate (2" ") and the plate placed above the1"" plate is the right ventral posterior intercalary plate (r.v.p.). The plates which always
contact the 1"" and 2"" plates are otherantapical plates, and those between these andthe postcingulars are posterior intercalary plates.
Balech's system is as follows; the antapicalseries consists of three plates which always
surround the sulcal posterior platelet. The left
plates is the first antapical plate (1" "), thecenter is the second (2" ") and the right is thethird (3" "). Other plates between these and thepostcingular series are posterior intercalaryplates.

243

A new nomenclature, especially in the hypotheca
In all species of Pyrophacus, three plates arealways present around the small posterior sulcal
platelet. These three plates are regarded as thefirst, second and third antapical plates. The
second one is the same as C.A.P. of Steidinger
and Davis (1976). One to five, or occasionallymore plates occupy the position between theantapical and postcingular series. These are
regarded as members of the posterior intercalaryseries.
In the cyst, two to four, occasionally fiveparaplates similar to these intercalary plates inshape and position form an archeopyle. Thissuggests that these intercalary plates are of one
plate series.
In P. steinii, additional plates that are usuallysmaller than the posterior intercalaries arepresent between the posterior intercalary andpostcingular series. In the present work, theseplates are newly named as additional posterior
intercalary plates (a.p.). They have never developed in other thecate dinoflagellates.
Similarity of the plate formula in related taxa
Fragilidinium
heterolobum
Balech ex
Loeblich, which is closely related to the genus
Pyrophacus in having a similar plate distribution
in the hypotheca. The plate formula of thisspecies was first suggested by Balech (1979) as
follows; Po, 4', 9", 12c, 7' ", 2" ", 1p and 6s.
But in the figure shown by Balech (1979, Fig. 3),
the 12c platelet is different in shape from othercingular platelets and occupies the position
between the cingulum and sulcus. If this platelet
is not seen as a part of the cingulum but as a partof the sulcus, the 7''' plate which directly
contacts this platelet is not a postcingular. Basedon this viewpoint, three antapical plates surroundthe small sulcal posterior platelet and the plate
formula in the hypotheca should be corrected
as follows; llc, 6' ",3" ", 1p and 7s. This plate
distribution around the sulcus is fundamentallythe same in both Fragilidinium and Pyrophacus.

KazumiMATSUOKA

244

Observation in unialgal culture
Many and various dinoflagellate cysts wererecovered from the surface sediments of Omura
Bay. Based on the morphological characteristics,
mentioned later in detail, the cysts identifiable
as T. vancampoae (Rossignol) were selected forunialgal culture. For morphological investigations, both living and empty cysts were observed
under optical microscope. Living cysts wereselected for germination and incubation experiments. Twenty living cysts were placed in a single
chamber of the culture dish and then eighteen
cysts were excysted and developed in thecate
vegetative cells. Most of these vegetative cells
were reproduced asexually, produced many
vegetative daughter cells. Furthermore, several
cells were continued to divide for about two
weeks. After several divisions, these thecate cells
became small spherical thecate cells.
Living cyst (PI. 36, Figs. 4a, b):-Living cysts
which are pale brown with many small sphericaloil or starch particles and one large red pigmented body are selected for the germination
experiment. Even cysts with breaks in the distal
extremities of large processes or the autophragmare excysted and produced normal thecal plates.
The cysts are ca. 80 /lm in lateral diameterand ca. 55 /lm in length. They are flattened
and nearly circular in apical-ant apical view.
Many large barrel-shaped processes ornament
the cyst body. The paratabulation indicated by
the processes and archeopyle is 5-8', 9-11",
Oc, 10-11'" and (4-5)" " + 2-4@ (Table 1).
The symbol (@) indicates the number of paraplates consisting of the operculum in the cyst,
and is common in this text and figures. The morphological features closely resemble those of
the empty cysts recovered from Omura Bay.
Based on these features, the living cysts areclearly identified as T. vancampoae.
Thecate form (PI. 37, Figs. 2-8, 10a-12;
PI. 38, Figs. 1, 3, 5-7, 10---13; PI. 39, Figs.
2, 4, 5-7):-Most of the living cysts were germinated within two to five days. After excystment, only one thecate vegetative cell (=germinated cell) appeared in the culture chamber.

This cell was larger than any of the subsequent
vegetative daughter cells. The plate formulaeof many thecate specimens produced fromliving cysts were investigated. As comparedwith the same observations made of many
thecate specimens collected from the planktonin Omura Bay.
As a result, the laboratory-excysted vegetative
cells show a relatively wide variation in numberof plates (Table 1). The cultured specimens havemore plates than those obtained from the plankton. In vegetative cells derived from the plankton
and excystment, however, the plates are arrangedin the usual apical, precingular, cingular, postcingular and antapical series. The fundamental
plate pattern in these specimens is as follows.
The apical pore platelet is roughly ellipsoidal,
but polygonal in detail, and its longest axis isslightly oblique (PI. 36, Fig. 7). The two apicalpores are linear and arched in shape, and thedorsal one is larger than the other. The apicalseries consists of six to eight plates. The l' plate
was asymmetrical and antero-posteriorly romboidal in shape and bears a small pore, probably
the "ventral pore", in its posterior part. Other
apical plates are pentagonal or hexagonal inshape and similar in height. One to two intercalary plates, which are usually smaller than
the apicals, are observed in some specimens.
The precingular series is made up of nine tofourteen plates. The first (1") and the last (9",10", 11", 12", 13" or 14") plates are shorterand always trapezoidal. The other plates aretrapezoidal or pentagonal in shape.
The cingulum is slightly indented and thenumber of platelets in it is basically the sameas the number of postcingulars. They always
remain connected to the hypotheca, when thetheca splits into two hemispherical parts. Each
plate has perforations arranged nearly parallelto the shallow cingular list. The postcingularseries consists of ten to fourteen plates. The first(1" ") plate is nearly orthogonal and the last(10' ", 11' ", 12' ", 13'" or 14' ") plate isroughly triangular but irregularly trapezoidal
in detail. The ventral plates are usually shorter
than the dorsal ones. The postcingular plates

245

805. Cyst and Theca of Pyrophacus steinii
Table 1. Paratabulation of living cysts used in incubation experiment and plate formula ofgerminated and subsequent daughter cells.
SpecimanPara tabulation of cyst

KM 001

not determined

7' 1a

13"

12c

12'" 2p lap

3 ....

KM002

not determined

8' Oa

13"

Ilc

11'"

4p Oap

3""

8'
8'

Oa
Oa

13"
11"

lIe
lIe

II'" 4p Oap
11'" 3p Oap

3 .. ..
3 .. ..

8' Oa

12"

ll1e

11'" 3p lap

3....

7'

00

12"

12e

12'" 3p Oap

3 ....

KM 003

7-'

9"

Oc

10'"

4 .... +X@

KM 00461' 10"

Dc

10'"

1....

Plate formula of germinated cell

Plate formula of daughter cells
not produced

not germinated

KM 005not determined

7' Oa

12"

121e

12'" 4p lap

3....

7'
7'

Oa
Oa

12"
12"

12c
12c

12'" 4p Oap
12'" 3p lap

3 .. ..
3 .. ..

Kl\I 006

not determined

6' la

9"

101e

10'" 2p Oap

3....

7'
7'

Oa
Oa

12"
12"

101e 10'" 4p Oap
121e 12'" 2p Oap

3 .. ..
3 .. ..

Oe

10'"

5 .... +2@

7' 1a

12"

121e

12'" 3p lap

3....

7'
8'
8'
S'
8'

la
Oa
2a
2a
2a

12"
12"
12"
12"
12"

12e
12c
12e
12e
12c

12'"
12'"
12'"
13'"
13'"

lap
Oap
Oap
lap
lap

3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..

Oa

12"

12c

12'"

KM 007

6'

10"

3p
3p
4p
4p
4p

KM OOS

7'

10"

Oc

11'"

4 .... +3@

7' Oa

12"

12e

12'" 3p Oap

3....

7'

3p Oap3 ....

KM009

8'

10"

Oe

10'"

6 .... +3@

6' 1a

13"

lIe

11'" 4p Oap

3....

7'

00 12" 121e 12'"
7' Oa 11" ll1c 11'"
7' Oa 12" 12e 12'"
6' 1a
1" 12e 11'"- - - - - - - - - - 12c 12'"---------- lIe 11'"- - - - - - - - - - lIe 11'"---------- lIe 11'"

3p
3p
4p
3p
5p
5p
5p
3p

lap
Oap
Oap
Oap
Oap
Oap
Oap
lap

3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..

Kl\I 010

6'

11"

Oc

10'"

4 .... +3@

7' Oa

11" lIe

11'" 4p Oop

3....

7'
7'
7'

3p
2p
4p
4p
4p
4p
3p
4p
3p

lap
Oap
Oap
Oap
Oap
Oap
Oap
Oap
Oap

3 ....
3· .. •
3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .... ·3 .. ..

KM 01151' 10"Oc

10'"

4 .... +X@

7' Oa 11" 12e12'" 2p Oap

3 ....

KM 012

6'

11"

Oc

10'"

5 .... +X@

7' Oa

11"

lIe

11'" 3p Oap

2 ....

7' Oa 11"
7' Oa 12"
7' la 11"----- --- -----------------------------

lIe
12c
lIe
12c
12e
13c
10e

11'"
12'"
11'"
12'"
12'"
13'"
10'"

3p
3p
3p
3p
3p
3il
2p

Oap
Oap
Oap
lap
Oap
Oop
Oap

3 .. ..
3 .. ..
3 .. ..
3 .. ..
2 .. ..
3 .. ..
3 .. ..

Kl\I 013

7'

10"

Oe

10'"

5 .... +3@

7' la

13"

14e

14'" 4p lap

3 ....

7' la 13"
7' la 13"----------

14c
14e
12c
12e
14c

14'"
13'"
12'"
12'"
14'"

4p
4p
2p
3p
4p

Oap
Oap
lap
Oap
lap

3 .. ..
3 .. ..
3 .. ..
3 .. ..
3 .. ..

11"

12'" 3p Oap

3 ....

Oa 12" 12c 12'"
Oa 11" ll1e 11'"
Oa 12" 12c 12'"
7' Oa 13" 13e 13'"
7' Oa 12" 13?e 13'"- - - - - - - - - - lIe 11'"---------- lIe 11'"---------- ~2e 12'"---------- 13e 13'"

not produced

not produced

KM014

not determined

7' 2a

10e

10'" 3p Oap

3....

Kl\I 015

not determined---------- 12e12'" 3p Oap

3....

----------

KM 016

not determined

7' Oa 12" 12c12'" 3p Oap

3....

7' la 12". 12c
7' Oa 12" 12e7' 0. 12" 12e---------- 12e---------- 12c

Oe

7' 1.

13'" 3p Oap

3....

7'
6'

61'

8"

KM 0207'10"Composite

5-8' 9--11"
Oe
10-11'"
4-5 .... +2-3@

KM 01S
Kl\I 019

8'"

5 .... +X@

12"

13c

not determined

7' 2a

13"

12e

12'" 4p Oap

3 ....

Oe

7' Oa

10"

10e

10'" 2p Oap

3 ....

10'"

4? .... +X@

6 S' 0-20
9--14"
10-14e10-14'"
2-4p 0-2ap
2-3 ....

C949·

data not provided

7' 3a15" Xc13'" 2p 5 .. ..

C 955·

data not provided

7' 2a 13" Xc

13'" 1p 5 .. ..

*Incubated specimens of Wall and Dale (1971)

la
1a

12"
12"

12c

12:" 3p12'" 3p12'" 2p12'" 4p12'" 4p

Oap 3 .. ..
lap 3 .. ..
Oap 3 .. ..
laP. 3''''Oap 3 ....

121e 12'" 3p Oap
13e 13'" 3p Oap

3 .. ..
3 .. ..

not produced

7'

Oa 10"
7' Oa 12"
6' 4a 12"
7' Oa 11"-- •.. ----.

lIe
12e
lIe
lIe
lIe

11'"
12'"
11'"
10'"
11'"

2p
3p
3p
2p
4p

Oap 3 .. ..
Oap ·3 .. ..
lap 3 .. ..
Oap 3 .. ..
Oap 3 .. ..

6 8'
0-4a
11 13"
10-14e10-14'"
2-5p O-lap
2-3 ....
8'

Oa

13"

..................... -Kazumi MATSUOKA246

KMOO 9

o
CYST

FORM

o
o

o

,----r----r---l
I
•
•
,

o

: : :/4tJi
.

I

:

. ,
:0

"...

.

.,

:

............... ~___ __ .l,,"If")

8' 10" Oc 10'" 6""+X@
APICAL VIEW,ANTAP I CAL VIEWJ
6' la 13" llc 11'" 4p Oap 3""

GERMINATED

THECATE

APICAL VIEWFORM

ANTAPICAL VIEW

Text-fig. 3a. Cyst-theca relationships of Pyrophacus steinii (Schiller) Wall et Dale based on incubation experiments. 3a; Specimen KM 009, 3b; Specimen KM 012, 3c; Specimen KM 013, 3d; Specimen
KM 020.
are also covered with coarse granules and perforated many small pores linearly arranged near
the cingulum. The plates possess distinct growth
or intercalary bands in mature spcimens. There
are three antapical plates that always surrounded
the small posterior sulcal platelet. The 1""
plate is an irregularly pentagonal to hexagonal
shape equatorially expanded. The characteristic

2" " plate is the largest and is nearly triangularin shape. The triangular and smaller 3" " plates
is also nearly in the sulcus and contacts thelast postcingular plate and 2"". The posterior
intercalary plates are also variable in number
from two to five. The Ip plate is usually nearlytrapezoidal and always contacts the 1"" and2" " plates and a few postcingular plates. The

805. Cyst and Theca of Pyrophacus steinii

247

KMal 2

o

CYST

FORM

J

o

o

o

o

0

I---y-----y---;
I:
I:
I:

:
•

•

Ii.

I
I

I

,,'

I
- __ '
A ____ I..•__ '" '"6' 11" Oc 9 1 " 6""+3@
ANTAP I CAL VlEW

APICAL VIEW

1
7' Oa 11" 11c 11'" 3p Oap 2""

GERMINATED

THECATE FORM

APICAL VIEWANTAPICAL VIEW
Text-fig. 3b.

last posterior intercalary plate is irregularly
hexagonal and occupies the position between
the 2" plates and dorsal postcingulars. The
other plates are elongated trapezoids and aresituated between the antapical and ventral postcingulars. There are a few additional plates between the posterior intercalary and/or antapicalplates and the postcingulars. These additional
posterior intercalary plates are usually smaller
than the other posterior intercalaries and arevariably pentagonal to hexagonal in shape. The

sulcal region consists of eight platelets (PI. 36,
Fig. 6; Text-fig. 4). The rectangular anterior
sulcal platelet is the largest and obliquely contacted the first and last cingular platelets. The
posterior sulcal platelet is roundly triangular
to ovoid in shape, and consistently surroundedby three antapical plates. The left sulcal platelet is larger than the right one. Both platelets
are situated just anterior sulcal platelet. The rightsulcal accessory platelet is roundly rectangular,
and larger, and is located between the lastKazumi MA TSUOKA

248

KMOl 3oo0,--"'---r---'CYST FORM

I

,

I

,

I
I

I
,

I

I

",,~.. 4.I ____

7' 10" Oc 10' " 5""+3@
APICAL VIEW

I

I
I
I

I

'

I
I
I
)

I,,"

~

ANTAPICAL VIEWI

7' la 13" 14c 14' " 4p lap 3""

GERMINATED
THECATE FORM

APICAL VIEWANTAPICAL VIEW
Text-fig. 3c.

cingular plate and the right sulcal platelet. The
left sulcal accessory platelet has a round triangular shape_ Two other small platelets are
occurred in the middle of the sulcal region:
median sulcal and anterior accessory platelets_
Small thecate form (PI. 40, Figs_ 1-12, Textfig. 6):-The vegetative cell germinated fromthe incubated cyst becomes gradually smaller
in diameter during asexual reproduction (Textfig. 5). After six to eight divisions, the proto-

plasm is divided into four or eight smaller masses
inside the parent theca (PI. 36, Fig. 1). Subsequently, four or eight small cells appear in theculture chamber. These small forms are also
covered with many thin thecal plates and platelets, but they are very different from the parent
cells in size and shape. These small cells are
ovoidal in shape, 36-37.2 pm long, 32-36 pm
wide and 32-36 pm thick (dorso-ventrally)(PI. 40, Figs. 1-4). Although there are slight805. Cyst and Theca of Pyrophacus steinii

249

KM a2 aooo
CYST FORMo----------.....
\
I

:

\
\

o

I

\
\

o

l

--- ....._-----,,/ '"II

7' 10" Oc 10'" 4?"I+X@

ANTAPICAL VIEW

APICAL VIEW

7' Oa 10" 10c 10'" 2p Oap 3" 11

GERMINATED
THECATE FORM

ANTAPICAL VIEW

APICAL VIEW
Text·fig.3d.
variations in number of plates, they total 38
to 39, excluding the sulcal and apical poreplatelets. The plates are smooth and transparent
without any ornamentation under optical microscope.
The apical pore plate is round hexagonal
and has many very small perforations scatteredaround the margin, and two large arched slits
in the centre (PI. 40, Figs. 5, lOa, 11). The
apicals consist of six to seven plates. The 1·

plate is nearly pentagonal in shape, but strongly
expands antero-posteriorly and has a smalland elongate perforation, possibly "ventral
pore" on its posterior part (PI. 40, Figs. 5, 12).
Other apical plates are irregularly pentagonalor hexagonal in shape and of similar height.
There are no anterior intercalary plates. The
precingular series consists of nine plates ofsimilar height. The 3", 4", 6" and 7" plates
are pentagonal and others trapezoidal.

Kazumi MATSUOKA

250

95

..

lUi 009•

KM OIl{D-I)•

K!1 012(0-1')

'" 85
u

OJ

..c

..... 80
o
a.
>,

:c 75
4-

o

~ 70

..

.....

-

OJ

!a 65
o

60

T

o

2

3

4

5

6

7

8

Number of cell divisions

Text-fig. 5. Decrease in thecal diameter in
relation to number of cell divisions.
2""

Text-fig. 4.
in the sulcus.

Plate and platelet distribution

The cingulum is relatively wide (0.11 to 0.13
of the cell length), laevorotary (left handed)
displacement of one cingular width. When the

Explanation of Plate 35
Figs. 1-3_ Tuberculodinium vancampoae (Rossignol) Wall
Fig.1. Fossil specimen from the Pleistocene upper Nishiyama Formation; apical view,
showing apical and precingular barrel-shaped processed, Loc. Haizume, Niigata Prefecture,
X ca. 250.
Fig. 2. Fossil specimen from the Pliocene lower Nishiyama Formation, antapical view,
showing attached operculum and antapical processes, and a somewhat damaged archeopyle (arrow), Loc. Haizume, Niigata Prefecture, X ca. 250.
Fig. 3. Fossil specimen from the late Miocene Shiiya Formation, antapical view, showing
attached operculum composed of three rectangular paraplates, Loc. Ishiji, Niigata Prefecture, X ca. 250.
Figs.4a-5b. Pyrophacus steinii (Schiller) Wall et Dale from plankton sample of Omura Bay.
Figs. 4a-b. Living thecate vegetative cell containing a large nucleus, many chromatophores
and food reserves. a; apical view, X ca. 310, b; antapical view, X ca. 310.
Figs. 5a-b. Vegetative cell theca, showing the distribution of major plates: 5a; apicalview, 5b; antapical view; plate formula, Po, 7', Oa, 12", 12c, 12' ", 3p, Oap and 3" .. ,X ca. 310.
Figs. 6a-7c. Tuberculodinium vancampoae (Rossignol) Wall from surface sediments of Omura
Bay.
Figs. 6a-c. Polar view, 6a; apical view, showing large apical and precingular processes andadditional small, spherical apical processes (arrow), X ca. 235, 6b; optical cross section,
6c; antapical view, showing hypocystal archeopyle (arrow), X ca. 235.
Figs. 7a-c. Lateral view, 7b; optical cross section, showing hypocystal archeopyle (arrow),
X ca. 235.

MATSUOKA: Cyst and Theca of Pyrophacus steinii

Plate 35

251

805. Cyst and Theca of Pyrophacus steinii

complete theca is broken and split into two
the cingulum remained attaches to the hypotheca. The cingulum consists of nine rectangularplatelets, wider than tall, and equatorially expanded. The 9c platelet somewhat invades thesulcus. The postcingulum also possesses nine
plates. Some are trapezoidal, and similar inheight to the precingulars. Other parts of the
hypotheca are insufficiently clear in detailbecause it is easily deformed. Judging from
relationships with the adjacent plates, there are
one or two posterior intercalary plates. Threeant apical plates always surround the posterior
sulcal platelets, and these are variable in shape.

The sulcus is narrow and almost straight, anddid not reach the centre of the hypotheca.
This area comprises of eight platelets of various
shapes· and sizes. The anterior sulcal platelet isthe largest in shallow U-shape. The posterior
sulcal platelet is also large and irregularly hexagonal. This platelet contacts the 1''', 9''',I" ", 2" " and 3"" plates and the left sulcal
platelet. The left sulcal platelet is large, L-shaped
and occupies the position just anterior theposterior sulcal platelet. The elongated rectangular right sulcal platelet does not contact
the posterior sulcal platelet. Four other small
platelets are located between the left and rightAP

VENTRAL VIEW

APICAL VIEWDORSAL VIEWANTAPICAl VIEW

SULCUS

Text-fig. 6.

Diagram of the small thecate from of Pyrophacus steinii (Schiller) Wall et Dale. Speci-

men KM 012 D1-l.

KazumiMATSUOKA

2p2

sulcals and the anterior sulcal platelet.
The plate formula of these small thecate
forms is interpreted as Po, 6-7', 9", 9c, 9' ",1-2p, 3" " and Ss.
Cyst and thecate forms obtained fromnet haul and sediment samples
Cyst form :-The polar view in T. vancampoae
is very different from the equatorial view. In
the polar view, in which orientation most cysts
are observed, the cyst is circular to roundly
Table 2. Paratabulation of empty cysts recovered from the surface sediments of Omura
Bay. The symbol @ indicates opercula in
the hypocyst. 'S' means small spherical processes on the epicyst.
Total number or processes

Paratabulation
12'"

5 .... +3fi

37 ... a@

10"

0,
0,

10'"

4· .. ·+3.

31 ... 3@

7'..-Is

10"

0,

12'"

4""+3 or 4@

33 ... 3 or 4@

6'

10"

0,

11'"

4 .... +3@

31 ... 3@

7'

10"

0,

9'"

3""+3@

29 ... 3@

140

9"

0,

9'"

7'

10"

0,

12'"

5-S""+XtP
3· .. ·+3@

32 ... 3@

7'

9"

0,

12'"

3""+3@

31 ... 3@

6'

9"

0,

9'"

4·.. ·+3@28'" aCil

8'

II"

0,

II'"

6 .... +3@

33 ... 3@

0,

13'"

8'
7·... Is

12"

7'

1O'"

6''''+3@

36'" ail

-6-8'

9-12"

0, 9-13'"

3-5(6),'''+3-4@

28-35+3-'lIiI

8-13"

-

3-11·.. •·-5-8'(7'10"

6-13'"
10'"

8 .... )*composite paratabulation of empty cystsof Omura Bay**composite paratabulation of cysts of Ivory
Coast (Wall & Dale, 1971)

reniform, while in the equatorial view, it is aslightly round rectangular with weakly developed
shoulders. The cyst wall consists of a thin,smooth and nearly transparent autophragm.,
The processes are hollow, and intratabular of
two types. One is large and barrel- to dumbeUshaped, because it consists of two sphericalparts with different diameters. In well-preserved
specimens, the distal extremities of these processes are expanded to be flare-like and connectedwith adjacent ones. In this way, they often makean outer cyst wall. The other type of processes,a simple sphere, is rare. The walls of both typesof processes are thin and smooth. These processes do not have any parasutural features atthe proximal bases. These processes are regularly
distributed in four latitudinal lines surrounded
the cyst body. Judging from their position
relative to the archeopyle and the plate distribution in the thecate form, these lines correspondto the apical, precingular, postcingular andantapical paraplate series. The apical' area consists of six to eight large processes and sometimes a few small spherical processes as well.
There is no process representing the apical poreplatelet in the thecate form. The precingulararea begins at the epicystal shoulder of the cyst
body and includes eight to ten large processes.
This area contained hardly any small spherical
processes. The postcingulum is relatively variablein number of processes and is composed of nine

Explanation of Plate 36
Modern cyst and thecate forms of Pyrophacus steinii (Schiller) Wall et Dale collected from surface
plankton of Omura Bay.
Figs. la-b. Gamete formation (?) showing eight small cells included within a normal vegetative
cell, X ca. 310.
Fig. 2. Hypnozygote (?), theca containing a living cyst identified as Tuberculodinium vancampoae (Rossignol) Wall showing arch eo pyle suture preparing for germination (arrow)(interference contrast optics), X ca. 310.
Figs.3a-b, Hypnozygote (?), theca containing a living cyst, X ca, 310.
Figs. 4a-b, Living cyst probably recently freed from its parent theca. 4aj apical-ant apical view,
X ca. 310, 4b; lateral view, X ca, 310.
Fig. 5. Hypotheca of vegetative cell, showing well developed growth band and many small
surface granules. SEM photograph, X ca. 700.
Fig. 6. Sulcus of the thecate cell. SEM photograph, X ca. 2500.
Fig. 7. Apical pore platelet of thecate cell. SEM photograph, X ca. 2500.

MATSUOKA: Cyst and Theca of Pyrophacus steinii

1aPlate 361b

805. Cyst and Theca of Pyrophacus steinii

to thirteen large processes. These processes occur
at another hypocystal shoulder. The an tap ical
area has three to five large processes and thearcheopyle, consisting of two to three, rarely
four or five paraplates which are released atexcystment. There are no processes or ornamentation between the pre- and post-cingular series.
Therefore, the paracingulum is represented by
the space between these two rows of processes.
The parasulcal area is also not reflected by any
morphological features.
Based on this evidence, most cysts recoveredfrom Omura Bay possess 27 to 37 pro,cesses,
including large and small spherical types andtwo to five paraplates corresponding to thearcheopyle.
Thecate cell bearing living cyst (PI. 36, Figs.
2, 3; Text-fig. 7):-The plankton sample collected from Omura Bay in June, 1983 and July,
Table 3.

253

1984 contained not only many thecate specimens identifiable as P. steinii (Schiller) but alsoa few living forms of T. vancampoae (Rossignol).
Furthermore, rare of thecate cells filled not with
protoplasm as observed at the motile stage butwith a cyst were found in it (PI. 36, Figs. 2, 3).
Two thecate specimens enclosing the living
cysts were examined for thecal tabulation andcyst paratabulation. One consists of eight apicals,
thirteen precingular, twelve cingulars, twelve
postcingular, three posterior intercalaries, three
antapical plates and one apical pore platelet.
Its plate formula is 8', Oa, 13", 12' ", 3p, Oap
and 3"". The para tabulation of the cyst included within the thecate cell is 6' with one small
process, 10", Oc, 10' " and ?" ", and its archeopyle is not clear. In another specimen, although
the plate formula in the epitheca can not be
determined, the hypotheca contains twelve

Plate formulae of thecae and paratabulation of living cysts contained
within, from plankton samples of Omura Bay in June, 1983.
Paratabulation on living cyst

Plate formulae of thecae
8(?)' Oa 13" 12(?)c12'" 3p Oap 3"". _. _ ... _.? - - -. - - -. 12'" 3p Oap 3""

6'+1s10" Oc 10'"X""

8'+5(?)s

10" Oc 10'"

6""+3@

THECATE FORM
8(?)' Oa 13" 12(?)c 12'" 3p

APICAL VIEW

Text-fig. 7.

CYST FORM
6'+18 10'1 Dc 10 111 Xliii

ANTAPICAL VIEW

Diagram of a theca containing a living cyst, collected from Omura Bay in June, 1983.

254

Kazumi MATS UOKA

postcingulars, three posterior intercalaries andthree antapicals. The paratabulation of the cyst
is interpreted as 8' (+ a few small processes),10", Oc, 10' " and 4" " + 3@. The archeopyleconsists of three nearly rectangular opercula,and has been already indicated by the boundaryof three paraplates. Trabecula or small spherical
processes are completely lacking. These paraplates are closely similar to the posterior intercalary plates in general shape, but smaller. Also,
the orientation of the opercula is clearly different from that of the thecate form. The diameterof the cyst is nearly half of the thecate cell andresembles that of the temporary cyst producedby the usual asexual reproduction.
Morphological variation in thecate form
Variations in the cell shape and the plate
pattern are seen in both field-collected andcultured specimens. Plates show wide variationsin shape and number, while the cell shape wasrelatively consistent.
Cell shape:-All field specimens and mostcultured specimens are lenticular in dorso-ventral
view and roundly reniform in polar view. Thisis one of the most stable characters in the thecate
form. But in speicmen labelled as KM 018 forexample, all of the thecate cells derived fromone cultured cyst are different from the progenyof the other cysts in cell shape (Pl. 38, Fig. 9).
They have a normal-lenticular epitheca and aroundly conical hypotheca, and these features
makes them longer than normal forms. On theother hand, the plate formula of these specimens
6-7', la, 12", 13c, 12-13", 3p, Oap and 3" "with minor variability in number of plate; but
this variation is quite similar to that of othercells.
Aberrant shape of plate:-The first apicalplate is occasionally divided in the middle into
two plates. In this case, the l' plate does notreach the cingulum and the ventral pore appearson the 1" plate (PI. 37, Fig. 2a; PI. 39, Fig. 2a).

Explanation of Plate 37
Modern cyst and thecate forms of Pyrophacus steinii (Schiller) Wall et Dale obtained in unialgal
culture.
Figs. 1-5. Pytophacus steinii (Schiller) Wall et Dale, Specimen KM 009.
Fig.!. Cyst after germination, showing much compressed cyst body, X ca. 330.
Figs. 2a-b. Newly germinated vegetative cell, 2a; epitheca, apical surface in ant apical view,
showing aberrant shape of the l' plate (arrow), X ca. 330, 2b; hypotheca, antapicalsurface in apical view, X ca. 330.
Fig. 3. Hypotheca of daughter cell, antapical surface in antapical view, X ca. 330.
Fig. 4. Epitheca of daughter cell, apical surface in antapical view, X ca. 330.
Fig. 5. Hypotheca of daughter cell, antapical surface in antapical view, X ca. 330.
Figs. 6-8. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 010.
Fig. 6. Hypotheca of newly germinated vegetative cell, antapical surface in antapical view,
showing additional small posterior sulcal platlet (arrow), X ca. 330.
Fig. 7. Hypotheca of daughter cell, antapical surface in antapical view, X ca. 330.
Fig. 8. Hypotheca of daughter cell, antapical surface in antapical view, X ca. 330.
Figs.9a-12. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 012.
Fig. 9. Cyst after germination, 9a; apical surface, X ca. 360, 9b; antapical surface showing attached operculum corresponding to three rectangular paraplates, X ca. 360. 'Figs. lOa-b. Newly germinated vegetative cell, lOa; epitheca, apical surface in apical view,
X ca. 400, lOb; hypotheca, showing two antapical plates, antapical surface in apicalview, X ca. 400.
Fig. 11. Hypotheca of daughter cell, antapical surface in antapical view, X ca. 330.
Fig. 12. Hypotheca of daughter cell, antapical surface in apical view, X ca. 330.

MATSUOKA: Cyst and Theca of Pyrophacus steinii

Plate 37

805. Cyst and Theca of Pyrophacus steinii

The posterior intercalary plates are normally
rectangular or elongatedly pentagonal. But thisplate series occasionally consists of two large
septagonal and one nearly triangular plates.
Furthermore, in specimens possessing extra
posterior intercalary plates, the shape of theposterior intercalary plates also becomes irregular(PI. 38, Fig. 13).
The second antapical plate was rarely absent(e.g. specimen labelled as KM 011) and thenthe first postcingular plate touched the second
antapical plate (PI. 37, Fig. lOb).
These aberrant plates appeared only in cultured specimens.
Number of plates:-The number of major
plates and cingular platelets is more variable
than the cell shape. The total number of plates
ranges from 31 to 41. The plate formulae offreshly germinated cells vary. The composite
formula is 6-8', 0-2a, 9-14", 10-14c, 1014' ", 2-4p, 0-2ap and 2-3" ". The mostcommon pattern is 7', Oa, 11-12", 12c, 12' ",3-4p, Oap and 3" ".
The progeny of these first cell has composite
plate formulae 6-7', 0-4a, 11-13", 10-14c,
10-14' ", 2-5p, o-lap and 2-3" ". The mostcommon pattern is 7', Oa, 12", 12c, 12' ", 3p,
Table 4.

255

Oap and 3" " (52 out of 155 specimens). The
total number of plates ranges from 31 to 43.
Clearly then, the plate formula of the daugh.
ter cells are frequently different from those of
the first germinated cells. For example, in specimen labelled as KM 020, the first germinatedcell has the formula 7', 2a, 11", lOc, 10' ",2p, Oap and 3" ". Within several days, morethan ten daughter cells are produced with plate
formula as follows: 7', Oa, 10", 11c, 11' ", 2p,
Oap and 3" "; 7', Oa, 12", 12c, 12' ", 3p, Oap·
and 3" "; 6', 4a, 12", 11c', 11' ", 3a, lap and
3" "; 7', Oa, 11", 11c, 10' " or 11' ", 2p, Oap
and 3" ".
The composite formulae of field specimens
are 6-7', Oa, 9-12", 11-13c, 11-13' ", 2-3p,
Oap and 3"", and the total number of plates
ranges from 31 to 37. Among them, the mostfrequent formula is 7', Oa, 12", 12c, 12' ", 3p,
Oap and 3" " for a total of 37 plates (in 76 outof 83 specimllns).
These data indicate that the cultured specimens are more in number of plates and variable
than the field spcimens.

Variation in numbers of plate of germinated cells and subsequent daughter cells in
incubation experiments and of normal vegetative cells in plankton sample.
Plate series

Germinated cells

Daughter cells

Apical plates
Anterior intercalary plates
Precingular plates
Total plates in epitheca

6-8 (7 )
0-2 (0)9-14 (11, 12)
16-22 (20)

6-8 (7 )
0-4 (0)11-13 (12)17-22 (19)(7 )09-12 (12)16-19 (19)Cingular platelets
Sulcal platelets

10-14 (12)8

10-14 (12)8

11-13 (12)8

Postcingular plates
Antapical plates
Posterior intercalary plates
Additional post. inter. plates
Total plates in hypotheca10-14 (12)2-3 (3 )
2-4 (3,4)
0-2 (0)
15-21 (18)

10-14 (12)2-3 (3 )
2-5 (3)0-1 (0)
15-21 (18)

11-13 (12)3
2-3 (3)0
16-19 (18)

Total plates

31-41 (39)33-43 (39)33-37 (37)

155

83

Number of specimens

17

Cells in plankton
6-7

Kazumi MATSUOKA

256

Discussion
Cyst morphology:-Based on morphologicalcharacteristics, the living cysts provided forincubation experiments were clearly identified
as T. vancampoae. In addition, several new
morphological features are noted as a result of
the present study.
As Wall and Dale (1971) have already mentioned, the number of paraplates corresponding
to the operculum is variable in number. It ranges
from two to five in the present cyst specimens.
The fossil Tuberculodinium rossignolae Drugg
is known to have two opercular paraplates
which consiered to be an important character (Drugg 1970). But the Miocene speci-

mens of this species shown by Williams andBrideaux (1975, pI. 34, figs. 2, 3) clearly has
three opercular paraplates similar to those of
T. vancampoae. Therefore, this character is notdiagnostic for T. rossignoiae.
Small spherical "processes" are also present
on the fossil species Tuberculodinium wallii
Drugg. But this species has these processes
more densely not only on the apicals but also
on the postcingulars, including the opercularparaplates, and the antapicals.
The para tabulation of the specimens collectedfrom Omura Bay is as follows; 5-7', 9-10",
10-11" , and 4-5" " + 2-3@. This is within
the range of variation indicated by Wall andDale (1971). In the specimens used in the in-

Explanation of Plate 38
Modern cyst and thecate forms of Pyrophacus steinii (Schiller) Wall et Dale obtained in unialgal
culture.
Fig. 1. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 012, hypotheca of daughter cell,showing aberrant shape of the 2" " plate (arrow), antapical surface in antapical view, X ca.
330.
Fig. 2. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 011, cyst after germination,
lateral view, X ca. 400.
Fig. 3. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 009, hypotheca of newly germinated vegetative cell, antapical surface in antapical view, X ca. 330.
Figs. 4a-6. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 013.
Figs.4a-c. Cyst after germination, 4a; apical surface, X ca. 260, 4b; optical cross section ofantero-posterior view, X ca. 260, c; antapical surface showing attached operculum composed of three rectangular paraplates, X ca. 260.
Fig. 5. Epitheca of newly germinated vegetative cell, apical surface in antapical view, X
ca. 260.
Fig. 6. Hypotheca of daughter cell, antapical surface in antapical view, X ca. 260.
Fig. 7. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 002, hypotheca of daughter cell,
antapical surface in apical view, X ca. 335.
Figs.8-11. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 018.
Fig. 8. Cyst after germination, showing somewhat damaged autophragm, X ca. 325.
Fig. 9. Lateral view of newly germinated vegetative cell, showing relatively normal epithecaand subspherical aberrant hypotheca, X ca. 325.
Fig. 10. Epitheca and hypotheca of daughter cell, showing lenticular epitheca, X ca. 325.
Fig. 11. Sulcus of daughter cell, apical surface in oblique apical view (interference contrast
optics), X ca. 640.
Fig. 12. Pyrophacus steinii (Schiller) Wall et Dale, Spcimen KM 003, epitheca of newly germinated vegetative cell, apical surface in antapical view, X ca. 325.
Fig. 13. Pyrophacus steiliii (Schiller) Wall et Dale, Spcimen KM 006, hypotheca of daughter cell,showing additional sulcal posterior platelet (arrow), antapical surface in apical view, X ca.
330.

MA TSUOKA: Cyst and Theca of Pyrophacus steinii

Plate 3879~__________~

805. Cyst and Theca of Pyrophacus steinii

cubation experiment, the paratabulation represented by the intratabular processes and thearcheopyle corresponds only roughly to thetabulation of the thecate form, except for the
cingulum and sulcus (which does not correspondat all). The number of processes plus opercularparaplates is usually fewer than the number ofthecal plates. These facts suggest that suchmorphological information as the number
and structure of plates and platelets in thethecate stage are. poorly reflected in the cyst
stage.
Plate formula of Pyrophacus steinii, and P.
vancampoae:-There are three taxonomic units
in the genus Pyrophacus, as several authors
have agreed, but the taxonomic positions ofthese units are uncertain.
Steidinger and Davis (1967) recognized one
species, one variety and one form as follows;
Pyrophacus horologicum, P. horologicum var.
steinii and P. Form B1 • According to theirobservations, the plate formula of P. horologicum var. steinii is 6-7', 0-la, 11-13",1113' ", o-lp and 5-S" " (6-7', o-la, 11-13",
11-13' ", 2-5p, o-lap and 3" " in my nomenclature), and P. Form Bl has 7-9', 2-Sa, 1315(16?)", 13-16' ", 0-6p and 7-11"" (79', 2-Sa, 13-15(16?)", 13-16' ", 4-Sp, 06ap and 3" " in my nomenclature). Based onthese data, they suggested that P. Form B1 is257

either another variety of P. horologicum or isan aberrant form.
Wall and Dale (1971) carried out a precise
statistical study of the plate formulae of thesethree taxa, and divided them into three species;
P. horologium, P. steinii, and P. vancampoae.
The plate formula of P. steinii is 6-7', Oa, 1113", 12c, 11-14' ", 1-2p and 4-6" " (6-7',
Oa, 11-13", 12c, 11-14' ", 1-3p, 1-2ap and3" " in my nomenclature) plus an apical poreplatelet with about eight sulcal platelets. P.
vancampoae is more variable in plate number
and its formula is 7-9', 0-9a, 13-15", 1216c, 12-17' ", 1-9p and 5-7"" (7-9', 09a, 13-15", 12-16c, 12-17' ", 2-4p, 1-9ap
and 3"" in my nomenclature) plus an apicalpore platelet with eight sulcal platelets. Its mostcommon formula is represented as S', Oa, 14",14c, 14' ", 1p and 6" " (S', Oa, 14", 14c, 14' ",3p, lap and 3" " in my nomenclature). Although
they recognized the presence of the morphologically intermediate forms between P. steinii
and P. vancampoae, and furthermore the possibility that these two species may be biologicalecotypes, they considered that these species
are different enough to warrant separation.
Balech (1979) rearranged these three species
described by Wall and Dale (1971) into two
species, but with P. vancampoae reduced to a
subspecies under the code of International

Table 5. Summarized plate formula of Pyrophacus steinii (Schiller) and its related taxa, according toseveral authors.

Pyrophacus Form BI

Pyrophacus horologicum

Author or locality

Plate formula

Taxon

7-9'

2-8a

13-lS(16)"13-16'"

0-6p
[4-Sp

7-11""
O-Sap 3"")

6-7'

O-la

11-13"

11-13'"

0-lp
[3-Sp

S-8""
0-lap

var. sleinii

Steidinger & Davis (1967)
3"")
----

Pyrophacus uancampoae

7-9'
(8'

0-9a
Oa

13-1S"
14"

12-16c14c

12-17'"
14'"

1-9p
1p

S-7""
6"")

PyropJiacus steillii

6-7'
(7'

Oa
Oa

11-13"
12"

12c
12c

11-14'"
12'"

1-2p
1p

4-6""
6"")

Pyrophacus stein;i subsp.

8'12-14"

12c

12-14'"

7'

12"

12c

12'"

3p

3""

9-14"
12"

10-14c12c

10-14'"
12'"

2-Sp
3p

0-2ap
Oap

Wall & Dale (1971)

3""

vancampoae

Pyrophucus stein;; subsp.

Balech (1979)

sieill;;Presenl specimens

6-8'
(7'

0-4a
Oa

3""
3'''')

From Omura Bay258

Kazumi MATSUOKA

Zoological Nomenclature, because the differences between P. steinii and P. vancampoae
are smaller than those between P. horologium
and P. steinii. According to him, the normal
plate formula of P. steinii is Po, 7', 12", 12c,
12' ", 3" ", 3p and 8s, and that of P. vancampoae
is basically Po, 8', 12-14", 12-14c, 12-14' ",3" ", 8s and 8-11p. Based on this, he consideredthat P. vancampoae is a subspecies of P. steinii.
In the specimens germinated from living cystsof Omura Bay, only a few may have formula
like that of P. vancampoae; Specimen labelled
as KM 002 was 8', Oa, 13", 11c, 11' ", 4p, Oap
and 3" "; specimen labelled as KM 013 was
7', 2a, 13", 12c, 12' ", 4p, Oap and 3" ". These
formulae do not agree with the most common
formula of P. vancampoae indicated by Walland Dale (1971). Furthermore, in the case of
specimen KM 013, progeny of the first germinated cell had the formula 7', la, 13", 13c,
13' ", 4p, Oap and 3" ". This formula is wellwithin the range of P. horologicum var. steinii
sensu Steidinger and Davis (1967), P. steinii
sensu Wall and Dale (1971) and P. steinii subsp.

steinii sensu Balech (1979).
Cyst form of Pyrophacus steinii:-Based on
the morphological characters, systs used in the
incubation experiments and those acquired bypalynological method can all be assigned to T.
vancampoae. There are not significant morpholgical differences between cysts from
Phosphorescent Bay (Wall and Dale 1971)
and from Omura Bay. Although the vegetative
cells obtained from the incubation experiments
showed greater individual variation in the plate
formula, they were clearly identifiable as P.
steinii. Furthermore, theca containing living
T. vancampoae cysts were found in the plankton.
These theca had the plate formula of P. steinii,
as well only P. horologium and P. steinii motile
cells were found in the plankton. No plankton
cells could be identified as P. vancampoae.
This means that T. vancampoae is also the cyst
form of Pyrophacus steinii.
Based on their incubation experiments, Walland Dale (1971) concluded that T. vancampoae
is the cyst form of P. vancampoae but they did
not discuss the cyst of P. steinii. GerminatedExplanation of Plate 39
Modern cyst and thecate forms of Pyrophacus steinii (Schiller) Wall et Dale obtained in unialgal
culture.
Figs.1a-2c. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 009.
Figs. la-f. Cyst after germination, 1a; apical surface, X ca. 285, 1b; optical corss section
in antero-posterior view, X ca. 285, 1c; ant apical surface, showing attached operculum
composed of three paraplates, 1d; enlargement of 1e, showing archeopyle, X ca. 570,
1e and 1£; lateral surface, X ca. 285.
Figs. 2a-c. Newly germinated vegetative cell, 2a; epitheca lacking the apical pore platelet,
showing aberrant shape of the l' plate (arrow), apical surface in apical view, X ca. 285,
2b; epitheca, showing lenticular shape, oblique lateral view, X ca. 285, 2c; hypotheca,
antapical surface in apical view, X ca. 285.
Figs. 3-7. Pyrophacus steinii (Schiller) Wall et Dale, Specimen KM 020.
Fig. 3. Cyst after germination, apical surface, X ca. 260.
Figs. 4a-b. Newly germinated vegetative cell, 4a; epitheca, apical surface in antapical view,
X ca. 260, 4b; hypotheca, showing the aberrant shape of the 1" " and 2" " plates, antapical surface in apical view, X ca. 260.
Fig. 5. Hypotheca of daughter cell, showing only two antapical plates; antapical surface
of antapical view, X ca. 260.
Fig. 6. Hypotheca of daughter cell, showing cingular platelets, optical cross section inantero-posterior view, X ca. 260.
Fig. 7. Epitheca of daughter cell, apical surface in apical view, X ca. 260.

MATSUOKA: Cyst and Th eca of Pyrophacus steinii

1aPlate 391c

259805. Cyst and Theca of Pyrophacus steinii

thecate cells obtained from Phosphorescent
Bay have following plate formula; C949 ... 7',
3a, 15", 15' ", 2p and 5" ", and C955 ... 7',
2a, 13' ", 1p, and 5" ", and 8', Oa, 13" (hypotheca unknown) according to Wall and Dale
(1971). The plate number of these specimens
are larger than the normal form of P. steinii;
but in my opinion, one of them, C955, is clearly
included within the range of P. steinii. Therefore,no clear separation can be made based on vegetative cell plate formulae, between P. steinii and
P. vancampoae obtained from Phosphorescent
Bay and Omura Bay.
Significance of small thecate form in life
cycle of Pyrophacus steinii (Text-fig. 8):-The
small thecate form of P. steinii is different fromnormal vegetative cells of P. steinii (Schiller)

in plate formula and cell shape, and most closely
resembles P. horologium except for the number
of apical plates. The latter species has only fiveto six plates, while the former form possesses
six to eight.
Steidinger and Davis (1967) reported that
P. horologicum is more spherical than P. steinii
and that smaller cells are found. The small
thecate forms derived from incubation are
similar in shape to these small and sphericalcells of P. horologium, but they are distinguishable from the latter in being ovoid in cell shapeand having a wider cingulum. This small forms
also differ form P. horologium in the plate andplatelet distribution of the antapicals and sulcus.
P. horologium possesses three antapical plates
surrounding the posterior sulcal plates, one ofdepauperating cell division ~Pyrophacus steinii

Temporary cyst~---_

conjugation?

Vegetative cell\fission\\\, Encystment?
I

I

I
I

'¥

-------~

Excystment ~rCU10dinium vancampoae,\~

PlanDzygote

Hypnozygote (Resting cyst)

LIFE CYCLE of Pyrophacus steinii (Schiller)
Text-fig. 8.

Life cycle of Pyrophacus steinii (Schiller) Wall et Dale. Solid line; observed process,dotted line; hypothesized process.

260

Kazumi MATS UOKA

which is characteristically large and triangular,
and others having consistent shapes and positions. These characters are also found in P.
steinii. Though this small thecate form also
possesses three antapical plates, none are large
and triangular. Furthermore, the structure of
the sulcus is different in the two. The anterior
sulcal platelet of the small thecate form isshallow U-shape, while this platelet of P. horologium, is nearly rectangular. The posterior
sulcal platelet of the small thecate form isirregularly hexagonal, but the corresponding
platelet of P. horologium is nearly ellipsoidal.
In the former, the last cingular platelet clearly
invades the sulcus, but the platelet of the latterdoes not.
Metzenauer (1933) reported the occurrenceof P. horologium sensu lato from the Indian
Ocean. The figured specimen (Matzenauer 1933,

p. 481, fig. 78) is noteworthy in no being lenticular but rather subspherical, with a thecacomposed of many plates and platelets as observed in normal vegetative cells. This sphericalform is also smaller (57 J.1.m in length and 59.5
J.1.m in width) than normal cells and apparently
resembles the present small thecate form. Unfortunately its plate formula is not clear andcannot be reconstructed in detail from his
original figure, so we cannot determine which
species of the genus Pyrophacus that specimen
is assignable to. However, the species ofMatzenauer differs from the small thecate formin being more spherical and in having a cingulum
without displacement. With respect to the life
cycle in P. steinii, it is significant that the small
thecate form appeared in the unialgal culture.
Stosch (1973) reported the appearance ofsmaller and light colored cells in cultures of the

Explanation of Plate 40
Small thecate form of Pyrophacus steinii (Schiller) Wall et Dale obtained in unialgal culture.
Figs. 1-2. Ventral surface in dorsal view, showing the displacement of the cingulum. Both specimens are somewhat elongated antero-posteriorly; 1, specimen KM 012-1, X ca. 690; 2, specimen KM 012-2, X ca. 550.
Figs. 3-4.
Optical cross section in lateral view, showing the theca; 3, specimen KM 012-2, X ca.
650; 4 specimen KM 012-2, X ca. 600.
Figs. 5-£, lOa-b. Plate distribution on epitheca.
Fig. 5. Apical surface in antapical view, showing small ventral pore in the l' plate (arrow),
specimen KM 012-3, X ca. 570.
Fig. 6. Apical surface in oblique apical view, specimen KM 012-4, X ca. 660.
Figs. 1 Oa-b. Apical surface in antapical view, showing the apical pore platelet and apicalplates (lOa), X ca. 590, and precingular plates (lOb), X ca. 590, specimen KM 012-2.
Figs. 7-9. Plate distribtuion on hypotheca.
Fig. 7. Nearly optical corss section of hypotheca, showing the sulcus and postcingularplates, specimen KM 012-3, X ca. 770.
Fig. 8. Antapical surface in oblique antapical view, showing the 6' ", 7' " and 8' " plates,
specimen KM 012-3, X ca. 770.
Fig. 9. Antapical surface in oblique antapical view, showing right precingular plates andsome antapicals, specimen KM 012-2, X ca. 630.
Figs. 11-13. Cell pressed under coverslip, ventral surface in dorsal view.
Fig. 11. Thecal plates and platelets constituting the theca, a few plates and platelets are
missing, specimen KM 012-1, X ca. 600.
Fig. 12. Enlargement of anterior ventral part, showing an apical pore platelet and the l'2',7',1",2",3" (part) and 8" plates, and a ventral pore on the l' plate (arrow), speci:
men KM 012-1, X ca. 1400.
Fig. 13. Enlargement of posterior ventral part, showing the distribution of sulcal platelets
specimen KM 012-1, X ca. 1325.
'

MATSUOKA: Cyst and Theca af Pyraphacus steinii

Plate 4032"'-I_ _- - - '

10 a

4

10b

12

13

805. Cyst and Theca of Pyrophacus steinii

freshwater gymnodinialean species, Gymnodinium pseudopalsutre Schiller and concluded that
this form was a gamete formed by depauperatingcell division. Later, Dale (1977) also observed
such smaller cells in the thecate species,
Peridinium faeroense. The present smaller
form is very different from the normal vegetativecell in its smaller size and more spherical shape.
This strongly suggests that this smaller form
may be a gamete of P. steinii, but confirmationof this will need to investigate on its nuclear
phase and to observe a zygote formation.
Conclusion
Living cyst identical with the fossil dinoflagellate Tuberculodinium vancampoae (Rossignol)
Wall produced the thecate species Pyrophacus
steinii (Schiller) Wall et Dale in incubation
experiments.
In the plankton of Omura Bay, thecate formof Pyrophacus steinii (Schiller) Wall et Dale
contained living cysts assignable to Tuberculodinium vancampoae (Rossignol) Wall.
These facts indicate that Tuberculodinium
vancampoae is also the cyst form of Pyrophacus
steinii Wall et Dale.
Pyrophacus vancampoae (Rossignol) is concluded to be a subspecies of P. steinii as follows:
Pyrophacus steinii (Schiller) Wall et Dale subsp.
vancampoae (Rossignol) Balech.
In the unialgal culture of Pyrophacus steinii
germinated from living cysts, a small thecate
form appeared. This form is very different fromthe normal vegetative cell in being smaller andmore ovoid. The plate formula of this from ismore similar to that of Pyrophacus horologium
than to that of P. steinii.
The morphological characteristics of thisform strongly suggest that it is a gamete.
Acknowledgment
The writer wishes to express his deep gratitude to Dr. G. Gain of Department of Oceanography, University of British Columbia for his
critical reading of the manuscript and valuablecomments, and to Dr. S. Iizuka, Professor at

261

Faculty of Fisheries of Nagasaki University for
his kind help in the field work in Omura Bay
and for his kindness of providing him the plankton sample of Omura Bay. Sincere thanks are
due to Dr. Y. Fukuyo, University of Tokyo forhis helpful discussion on the morphology of thegenus Pyrophacus and to Professor W. R. Evitt
at Stanford University for giving the present
writer an opportunity to present this paper at
the Alfred Eisenack Memorial Session in the
VI International Palynological Conference at
Calgary and valuable suggestions. He also thanks
to Professor K. Takahashi at Nagasaki University
for his continuous encouragement. This work
was partly supported by Ministry of Education,
Science and Culture, the Government of Japan
under the Grant in Aid for Scientific Program(No. 5854058).
References
Balech, E. (1979): El genero Pyrophacus Stein(Dinoflagellate). Pysis, sec. A. Buenos Aires,
38 (94), p. 27-38.
Dale, B. (1977): New observation on Peridinium
faeroense Paulsen (1905), and classificationof small orthoperidinioid dinoflagellates.
Br. Phycol. Jour., 12, p. 242-253.
Drugg, W. S. (1970): Two new Neogene speciesof Tuberculodinium and one of Xenicodinium (pyrrhophyta). Proc. Bioi. Soc. Wash.,83, p. 115--122.
Harada, K. (1984): Study of dinoflagellates fromthe submarine strata at the Kansai International Airport in Osaka Bay off Senshu,
Central Japan. In Nakaseko, K. (ed.) "Geological survey of the submarine strata at
the Kansai International Airport in Osaka
Bay, Central Japan, p. 77-90, Rept.
Calamity Sci. Inst., Osaka, Japan.
Harland, R. (1983): Distributuion maps ofrecent dinoflagellate cysts in bottom sediments from the North Atlantic Ocean andadjacent seas. Palaeontology, 26, p. 321387.
Matsuoka, K. (1976): Paleoenvironmental studyof the Saho and the Saidaiji Formations
from a view point of palynology. Bull.
Mizunami Fossil Mus., 3, p. 99-117.
--(1983): Late Cenozoic dinoflagellates andKazumi MATSUOKA

262

acritarchs in the Niigata district, Central
Japan. Palaeontographica, Abt. B, 187, p.
89-154.
- - (1985): Distribution of the dinoflagellate
cyst in surface sediments of the Tsushima
Warm Current. Quaternary Res., 24, p. 112.
Matzenauer, L. (1933): Die Dinoflagellaten desindischen Ozeans (mit Ausnahme derGattung Ceratium). Bot. Arch., 35, p. 437510.
Nagasaki University (Faculty of Fisheries)(1976): Report of investigation on marine
environments of Omura Bay for policies
against the water pollution, 114 pp., Nagasaki Prefectural Government.
Rossignol, M. (1962): Analyse pollinique desediments marins Quaternaries en IslaiH.
II. Sediments Pleistocenes. Pollen et Spores,
4, p. 121-148.
Schiller, J. (1935): Dinoflagellatae (Peridineae).
In 'Rabenhorst's Kryptogamen Flora vonDeutschland, Osterreich und der Schweis'.
Akad. Verlags. Leipzig, 10, Abt. 3, Teil 2,
Lieferung 1, p. 1-160.

Steidinger, K. A. and Davis, J. T. (1967): The
genus Pyrophacus with a description of a
new form. Fla. Bd. Conserv. Mar. Lab.
Leaf/etSer., 1, p.1-8.
Stein, F. R. von (1883): Der Organisms derinfusionsthiere. Abt. III, Heft II. Verlag
von Wiehelm Engelmann, p. 1-30.
Stosch, H. A. von (1973): Observations onvegetative reproduction and sexual life
cycles of two freshwater dinoflagellates,
Gymnodinium pseudopalustre Schiller and
Woloszynskia apiculata sp. nov. Br. Phycol.
Jour., 8, p. 105-135.
Wall, D. (1967): Fossil microplankton in deepsea cores from the Caribbean Sea. Palaeontology, 10, p. 95-123.
-and Dale, B. (1971): A reconsideration ofliving and fossil Pyrophacus Stein, 1883
(Dinophyceae). Jour. Phycol., 7, p. 221235.
Williams, G. L. and Brideaux, W. W. (1975):
Palynological analysis of Upper Mesozoic
and Cenozoic rocks of the Grand Banks,
Atlantic continental margin. Geol. Surv.
Can. Bull., 236, p. 1-163.

Pyrophacus steinii (SCHILLER) WALL et DALE, 1971 (7)'/:A I- t IbfMd*: Pyrophacus
steinii (SCHILLER) WALL et DALE (J)"/:A I- iI~~F"JN.LHf7J.ill~(7)*5*iI' GB,ij GiI'v::' c':;ht-=.oTIlberculodinium vancampoae (ROSSIGNOL) i:: ji'i'j:;:Ec':;h ~1:"/:A r ii, G ~5f Lt-=.itfflik - 1'rm1:{tIt. iJH.&m;71J(7)~flHfJ:lll~I::'£-?\"-C Pyrophacus steinii I::..@i;-r~ t ~ht-=.o ~ GI::' T.
vancampoae t ji'i'j:;:Ec':;h~~1:'/:A r ~~~ 1...t-=. Pyrophacus steinii (7)itff'lfJc -1'r1tl!:f*iI'*tt~(7) ~*(7) 7' 7 :/? r :/llF,j,U' G t)!:j, <~ Gh t-=.o .::: h G (7)~;pH;:: J: ~ t, T. vancampoae It
P. vancampoae t.:r,r-r:t.. < P. steinii (7)"/:A r '(. t j; IJ, '1 t::. P. vancampoae It P. steinii(7)~~-r:~~t~~c':;h~.

~~~~Trans. Proc. Palaeont. Soc. Japan, N. S., No. 140, pp. 263-273, pIs. 41-44, December 30, 1985

806. A NOTE ON AN INOCERAMID SPECIES (BIV AL VIA) FROM THE
LOWER CONIACIAN (CRETACEOUS) OF HOKKAIDO*TATSURO MATSUMOTO
c/o Department of Geology, Kyushu University 33, Fukuoka 812
and

MASA YUKI NODA
Minami·Oita Junior High School, Oita 870

Abstract. A large number of well preserved specimens from the limited thickness of fine-grained sandy siltstone in the lower part of the Coniacian sequence
along the Pombets-Gono-sawa of the Mikasa [Ikushumbets] area, central Hokkaido,
is regarded as representing a population of a single species which can be identified
with Inoceramus rotundatus Fiege. We have examined statistically certain measurable characters on this sample (N=25) and described the extent of variation. The
ratio of shell length to height is fairly constant, whereas that of breadth to heightvaries considerably. There is variation in the appearance and strength of major ribs
and also in the distinctness of minor rings. Some specimens are thus fairly close
to a form which has been called 1. waltersdorfensis hannovrensis Heinz, but as
there is gradation from the typical form of I rotundatus, they are included in thesame species. I. rotundatus characterizes the lower part of the tripartite Coniacianin the sequence of the studied area. 1. uwajimensis Yehara is occasionally foundtogether with I. rotundatus, but it is more prolific in the middle part of theConiacian sequence. The fossils associated with 1. rotundatus include Didymotis
akamatsui (Yehara), Forresteria (Reesideoceras) petrocoriensis (Coquand) andHarleites cf. H. harlei (Grossouvre).

called the Takiyoshi-zawa by some people)
in the Mikasa [="Ikushumbets"] area, central
Hokkaido, give one of the reference sequences
for the Coniacian in Japan. We have obtained
there numerous specimens of a bivalve species,
which we identify provisionally with Inoceramus
rotundatus Fiege.
l. rotundatus was described by Fiege (1930),
Troger (1967), Kauffman (in Herm et al., 1979)
and Keller (1982) from central Europe. The
characters shown by the population of thisspecies at Pombets-Gono-sawa in Hokkaido
may not be quite identical with those at the

Introduction
On the occasion of the Symposium on the
Cretaceous Stage Boundaries in Copenhagen,20th October 1983, one of us presented apaper on the so-called Turonian-Coniacianboundary in Japan. As has been described inthat paper (Matsumoto, 1984), the outcrops
along the Pombets-Gono-sawa (which may be*Received December 6, 1984; revised manuscript received May 12, 1985; read February 2,
1985 at University of Tokyo.
263

264

Tatsuro MATSUMOTO and Masayuki NODA

type and other localities in central Europe. In
this paper we describe the species on the basisof our material.
Our study is based mainly on numerous
specimens from a particular member of theUpper Yezo Group exposed along the narrowcreek (stream) of the Pombets-Gono-sawa for
a restricted extent. This member, about 20 min thickness, consists of fine-grained sandy siltstone and is situated in the lower part of thewhole sequence, about 65 m, of the Coniacian.
The localities and the stratigraphic column havebeen already shown by one of us (Matsumoto,1984, fig. 4) and are reproduced here withpermission (Text-fig. 1). The most prolificoutcrop is loco Ik 2716 and the next is loco
Ik 2710. Fossiliferous nodules from each locality
may be indicated as, for instance, Ik 2716 a,b etc. There are some other nearby localities.
Some specimens are provisionally kept in theCollections of one of us (M.N.), which areindicated under JG. [Jonan Geological Collection, Oita], and others in the Type Room of
Geological Collections, Kyushu University, Fukuoka, indicated under GK. Those which havebeen transferred from JG. to GK. have double
numbers.
Palaeontological description
Family Inoceramidae Zittel, 1881
Genus Inoceramus Sowerby, 1814
Type species:-Inoceramus cuvierii Sowerby,
1814.
Remarks:-Aside from Mytiloides Brongniart,
1822 and Sphenoceramus Boehm, 1915, which
we regard as independent genera, Inoceramus
has been subdivided into several subgenera. 1.
rotundatus Fiege, described below, may bereferable to a subgenus which is different from
Inoceramus (Inoceramus), but we have not yet
arrived at a definite conclusion about its subgeneric assignment. As Kauffman (in Hermet al., 1979, p. 68) suggested, we presume
that its systematic position may be somewhere
between 1. (Inoceramus) and typical 1. (Cremnoceramus) Cox, 1969, whose type species is

1. inconstans Woods, 1911. Kauffman (op.
cit.) described it under Cremnoceramus witha query.

Inoceramus rotundatus Fiege, 1930

PI. 41, Figs. 1-4; PI. 42, Figs. 1a-ub;
PI. 43, Figs. 1a-11;PI. 44, Figs. 1-8.
1930. Inoceramus inconstans rotundatus Fiege,
p. 42, pI. 7, fig. 32; pI. 8, fig. 31; textfig.3.
1967. Inoceramus rotundatus Fiege; Troger, p.
110, pI. 12, figs. 5, 6; pI. 13, figs. 1013.
1979. Cremnoceramus ? rotundatus (Fiege);
Kauffman in Herm et al., p. 68, pI. 9,
figs. A, C.
1982. Inoceramus rotundatus Fiege; Keller, p.
114, pI. 8, fig. 2.
Lectotype:-The specimen illustrated by Fiege,
1930, pI. 7, fig. 32, from Schacht [Shaft]
Preussen III, depth 156 m of Rhein-Westfalencoal-field, designated by Brliutigam (1962) (seeKeller, 1982).
Material of the description below:-GK. H
10130 from loco Ik 2786 [=Ik 2118] collectedby T. Takahashi; GK. H 10131 [=JG. H 2859]
from loco Ik 2714 c; GK. H 10132 [JG. H
2868] from loco Ik 2716 h; GK. H 10133-H
10135 [JG. H 2895 A, C, D], GK. H 10136[JG. H 2861], GK. H 10137-H 10140 [JG. H
2872 A-D] , JG. H 2894 and JG. H 2896 fromloco Ik 2716 q; JG. H 2856, JG. H 2867 and
JG. H 2870 from loco Ik 2716 n; JG. H 2869
from loco Ik 2716 k; GK. H 10141 [JG. H
2900] from loco Ik 2716 d; JG. H 2874 fromloco Ik 2710k; JG. H 2871A, B, JG. H 2873, andJG. H 2897 A-D from loco Ik 2716 (undivided);
JG. H 2857, JG. H 2860, JG. H 2862, JG. H
2863, JG. H 2864, JG. H 2865 and JG. H 2866from loco Ik 2710. There are also many otherspecimens of imperfect preservation from thesame localities as above and also from loco Ik
2726. Almost all collected by us with the aid of
Messrs. T. Takahashi, S. Uchida and K. Muramoto in the Pombets-Gono-sawa [=Takiyoshizawa] , Mikasa. A thin, prismatic, inner shelllayer is preserved in most of the above speci-

806. A Coniacian Inoceramid Species
N

265

TERTIARY

Legend2703 ................. .

" ,

,

A

8
100m

2713···············,.

,C
0
TERTIARY
E

G

--+--

H

---------.

J

=

K

CONIACIAN

TURONIAN

Text-fig. 1. Route map of the Pombets-Gono-sawa, with a stratigraphic profile. Locality numbers
should have prefix Ik. Legend - A-D for profile-A: fine-grained sandy siltstone, B: silty fine-grainedsandstone, C: thick bedded sandstone, D: tuff, E: unconformity, F: fault ·(observed), G: fault (inferred), H: anticline, I: stage boundary, J: path (partly damaged), K: small scale dam; Abbreviation of
selected species - Ia: Inoceramus (Platyceramus) amakusensis, 1m: I. mihoensis, Ir: I. rotundatus, It:
I. tenuistriatus and L teshioensis, Di: Didymotis akamatsui, Fp: Forresteria (Reesideoceras) petro-coriensis, Lp: Lymaniceras planulatum.

266

Tatsuro MATSUMOTO and Masayuki NODA

Table 1.

Measurements of well preserved specimens of I. rotundatus from the Pombets-Gono-sawa(linear dimension in mm).

Specimen

valve

h

1

H

L

b

s

C<,~

r

6

l/h

b/h

L/H

s/l

JG.H2856

R

25.0

24.3

26.0

25.3

10.8

11.0

128 0

115 0

73 0

0.97

0.43

0.97

0.45

2857

L

51.7

49.8

54.1

52.0

20.2

25.0

105 0

134 0

62 0

0.50

2859a

L

24.3

23.8

26.2

25.0

7.3

15.0

98

0

130

61

2859b

R

23.7

22.9

25.3

23.0

8.0

14.1

100 0

2860a

L

62.2

52.0

69.4

60.3

22.8

29.0

2860b

R

61.2

52.4

66.2

58.4

20.6

2861c

R

17.1

16.8

17.6

16.0

2862a

L

25.9

25.0

29.4

2862b

R

27.7

26.4

2866

R

23.0

2868

R

2869

L

2871

0.96

0.41

0.96

0

0.98

0.30

0.95

0.63

128 0

61 0

0.97

0.34

0.91

0.59

108 0

126 0

66 0

0.84

0.37

0.87

0.56

-

98

0

132

67

0

0.87

0.34

0.88

-

5.2

10.0

107 0

117 0

59 0

0.98

0.30

0.91

0.60

25.4

9.0

16.1

100 0

140 0

57 0

0.97

0.35

0.86

0.64

29.9

26.3

9.1

16.1

93 0

135 0

52 0

0.95

0.33

0.88

0.61

22.4

26.0

23.5

7.5

12.5

105 0

133 0

63 0

0.97

0.33

0.90

0.56

37.6

33.7

38.2

35.6

12.0

17.4

107

130

62

0

0.90

0.32

0.93

0.52

40.5

37.4

44.4

40.8

15.2

24.5

103 0

-

62 0

0.92

0.38

0.92

0.66

R

30.0

28.6

33.7

32.2

11.8

15.0

103 0

138 0

63 0

0.95

0.39

0.96

0.52

2872a

L

20.6

18.2

22.0

19.9

8.2

11.5

102

0

135

0

66 0

0.88

0.40

0.90

0.63

2872b

R

19.5

18.4

20.7

19.3

7.4

11.3

115 0

137 0

62 0

0.94

0.38

0.93

0.61

2873

R

26.8

26.6

29.4

29.0

7.8

16.7

111

117

61

0

0.99

0.29

0.99

0.63

2874

R

19.8

18.1

20.9

20.2

6.2

10.3

105 0

128 0

65 0

0.91

0.31

0.97

0.57

2894

R

-

-

24·.0

24.0

5.4

-

100 0

132 0

54 0

-

-

1.00

-

2895d

L

22.5

21.7

25.9

21.8

9.3

11.7

102

0

132

62

0

0.96

0.41

0.84

0.54

2896

R

23.6

23.0

26.0

24.0

9.7

13.6

108 0

131 0

60 0

0.97

0.41

0.92

0.59

2897a

R

21.8

20.4

22.4

20.4

7.6

13.1

104 0

-

70 0

0.94

0.35

0.91

0.64

2897b

R

25.6

24.2

26.7

24.0

7.1

12.3

108

0

136

0

66

0

0.95

0.28

0.90

0.51

2897c

R

16.6

16.5

16.6

15.9

6.7

10.3

122 0

132 0

71 0

0.99

0.40

0.96-

0.62

2897d

L

25.0

24.0

27.8

23.8

9.9

12.9

1020

131 0

63 0

0.96

0.40

0.86

0.54

2900

R

19.4

19.2

21.4

-

7.7

9.1

112 0

-

62 0

0.99

0.40

-

0.47+

0

0

0

0

0

0

0

L: left, R: right, h: height, I: length, H: maximum linear dimension from beak to ventral extremity,
L: maximum linear dimension perpendicular to H, b: breadth, s: length of hinge-line; a: anterior
hinge angle,~: angle of umbonal inflation (nearly equal to or slightly smaller than a in this species),'"(: posterior' hinge angle, 0: obliquity (angle between hinge-line and H).

Explanation of Plate 41
Figs. 1-4. Inoceramus rotundatus Fiege
1. GK. H10131 from loc. Ik 2714c; left (a) and right (b) valves and their anterior view (c),x 1.5. 2. GK. H10132 from loc. Ik 2716h; right valve (a) and its posterior view (b), x 1.
3. JG. H2857 from loc. Ik 2710r; left valve (a) and its anterior view-(b), x 1. 4. JG. H2860
from loc. Ik 2710r; right (a) and left (b) valves and their anterior view (c), x 1.
The specimens figured in Plates 41-44 were all collected by the authors with the aid of
Messrs. T. Takahashi, S. Uchida and K. Muramoto in the Pombets-Gono-sawa [=Takiyoshi-zawa],
Mikasa area. Photos (Pis. 41-44) by M. Noda without whitening.

MATSUMOTO and NODA: A Coniacian Inoceramid Species101cPlate 41

806. A Coniacian Inoceramid Species
mens, although it is parJ:lY taken away.
Specific characters:-Shell small to moderate
in size, nearly equivalve, typically with moderate
and rather uniform convexity. Outline subrounded to subquadrate, slightly higher thanlong, with hinge-line somewhat longer than ahalf of shell length ; anterior part inclined steeply,
slightly concave near the umbo, showing almost
linear margin; ventral margin well rounded,passing gradually to arcuate posterior margin;
angle between posterior margin and hinge-line
obtuse ('Y ~ ca. 130° on the average), showing
flattened edge. Beak blunt, anterior and slightly
projected above the hinge-line. Axis of growthnearly straight or slightly concave anteriorly,

267

with average inclination (0) of about 63°.
Surface ornamented with fine concentric
raised lines or rings and concentric ribs of weak
to moderate intensity, showing variation withgrowth and also between individuals.
Biometry:-Measurements on the undeformed specimens (N=25) are shown in Table
1. We mentioned below that the small specimens
are mostly immature. Some of the biometricalcharacters show generally allometry in relative
growth. The statistics is, therefore, made in
two subgroups with the boundary at the growthstage of 25 mm in h, as shown in Tables 2 and3 respectively. As is clear from Tables 2 and 3,
the difference of mean value in each character

Table 2. Biometric characters of the studied sample of I. rotundatus (hCharacters

a

~

N

13

m

< 25 mm).

0

llh

blh

L/H

sll

13

'Y
11

13

12

12

12

11

106.2°

106.2°

130.5°

62.8°

0.957

0.361

0.925

0.588

s

6.78°

6.78°

5.20°

4.49°

0.03370.04400.04120.0336

v

6.38

6.38

3.98

7.15

3.52

12.19

4.45

5.71

N: sample size, m: mean value, s: standard deviation, v: Pearson's coefficent of variation, otherletters as for Table 1.
Table 3. Biometric characters of the studied sample of 1. rotundatus (h ~ 25 mm).

'Y
11

0

llh

blh

L/H

sll

12

~
12

12

12

12

12

11

m

105.5°

105.5°

130.4°

62.8°

0.936

0.358

0.915

0.558

s

8.62°

8.62°

8.09°

5.20°

0.04480.04730.04640.0675

4.79

13.21

5.07

12.10

Characters

a

N

v

8.28

6.20

8.17

8.17

Table 4. Biometric characters of the studied sample of I. rotundatus.
Characters

a

~

'Y

0

llh

llh
H=20mm

blh

L/H

sll

N

25

25

22

25

24

22

24

24

23

m

105.8°

105.8°

130.4 °

62.8°

0.946

0.953

0.359

0.920

0.537

s

7.37°

7.37°

6.49°

4.65°

0.03940.03070.04380.04230.0574

u

6.96

6.96

4.97

7.40

4.16

3.22

12.19

4.60

10.01

Tatsuro MATSUMOTO and Masayuki NODA

268

T
100
90
80
70

r=O.9704

r=O.9929

60

T = O.348h l • 004

30

1=1.241h O. 917

20

50
40

30

..

10
9
8

20

'.

7
6
5

10
9
8~------_,----~--~~--r-~~~~

3+--------,----~--,-_,--r_~~~~

Text-fig. 2. Diagram showing the averagerelative growth of shell height and shell length
in a studied sample of I. rotundatus.

Text-fig. 3. Diagram showing the averagerelative growth of shell height and shell breadth
in a studied sample of I. rotundatus.

is a little, which is less than the significant limitof Student's t-test. This allows us to summarize
totally the measured characters in Table 4,
regardless of the difference in growth-stage ofthe examined specimens.
Both the reduced major axes demonstrated
in Text-figs. 2 and 3 show the monophasic allometry. In the relative growth between shellheight and breadth, the growth index (a) is afairly good approximation of 1, which is clearly
within the range of isometry, and the growthindex (a) of shell height and length shows aslightly negative allometry (Hayami and Matsukuma, 1971, p. 150, 151).
Descriptive remarks:-Many of the examined

specimens are smaller than the lectotype andcertain other illustrated examples from Germany.
They show concentric rings fairly well, whereas
their concentric ribs are weak or very faint. As
will be discussed later, we regard at least someof them as immature.
There are, however, specimens of moderate
size. They have ribs of moderate intensity andare close to the lectotype. JG. H 2860 (PI. 41,
Fig. 4) is an examle of such a form. Although
it is represented by the internal mould for themost part, fine concentric rings are also discernible on the early middle part where theinner shell layer is preserved. On its late partthe rings are more distinct and impressed even

10

20

30

40

5060708090100h

10

20

30

40

50 60

Explanation of Plate 42
Figs. 1-6.
Inoceramus rotundatus Fiege
1. JG. H2766 from loco Ik 2710r; right valve (a) and its posterior view (b), x 1.8. 2. GK.
H10134 from loco Ik 2716q; right valve (a) and its posterior view (b), x 1.8. 3. JG. H2871Bfrom loco Ik 2716; left valve (a) and its anterior view, x 1. 4. JG. H2869 from Ik 2716k;
left valve (a) and its anterior view (somewhat secondarily compressed) (b), x 1. 5. GK.
H10133 from loco Ik 2716q; left valve (a) and its posterior view (b, above), x 1. 6. JG.
H2863 from loco Ik 2710; anterior view of both valves (a) and left valve (somewhat deformed) (b), x 1.5.

MA TS UMOTO and NODA: A Coniacian Inoceramid Sp ecies

Plate 42

806. A Coniacian Inoceramid Species"

on the internal mould. GK. H 10131 (PI. 41,
Fig. 1) has distinct and regular ribs, although
it is not so large as JG. H 2860.
GK. H 10132 (PI. 41, Fig. 2), JG. H 2857
(PI. 41, Fig. 3), JG. H 2862 (PI. 43, Fig. 9),
JG. H 2871 A (PI. 43, Fig. 8) and some others
have somewhat weaker concentric ribs thanthose of the above two, but cannot be separated
as a different species for this reason alone. Theyshow a uniform or gradually changing convexity
like the more strongly ribbed form, although
the ratio of breadth to height (b/h) varies considerably from a specimen to another. Fine
concentric rings are also discernible where theshell layer is preserved on these specimens.
The ribs are regular in GK. H 10131, JG. H
2857 and JG. H 2862, slightly irregular in
JG. H 2860, and more irregular in distance andstrength in GK. H 10132 and JG. H 2871. They
are occasionally denser as in JG. H 2869 (PI.
42, Fig. 4), in which some ribs are stronger thanothers. Incidentally, this specimen resembles
well a figured example from Germany (Troger,
1967, pI. 2, fig. 6 = Andert, 1934, text-fig. 7 c).
In many of the above·mentioned specimens
the major ribs are weak or indistinct or evenhardly perceptible on the younger part of theshell and well perceptible ribs begin to appear
at dissimilar growth-stages among individuals.
JG. H 2863 (PI. 42, Fig. 6) is an example inwhich distinct major ribs appear at a later stage
than in other specimens, although it is represented by the internal mould for the mostpart and is secondarily distorted. When thethin shell layer (i.e. inner prismatic layer inmost cases) is preserved, fine concentric rings
or raised lines are more clearly shown than the
faint or poorly developed major ribs on theyoung part in most of the specimens of moderate
size (i.e. more than 25 mm in height).
In many of the smaller specimens, the concentric rings or raised lines predominate andthe major ribs, if present, are weak or hardly
perceptible in the umbonal part. This is quite
similar to the feature seen on the young partof the specimens of moderate size mentioned
above. Therefore, we regard most of the smaller269

specimens as immature. They are fairly numerous, but some of them occur together with apresumably adult shell in one and the same
nodule (for instance, see PI. 44, Figs. 7, 8).
In a few specimens there is a sudden change
or geniculation in the convexity of the valve ata certain growth-stage. JG. H 2871 B (PI. 42,
Fig. 3) and JG. H 2895 C (PI. 42, Fig. 2) are
examples which show such a feature in thelate stage of their small shell. They occur together with the valves of uniform or graduallychanging convexity in the same bed (loc. Ik2716) or even in the same nodule (Ik 2716 q).
GK. H 10130 (PI. 43, Fig. 4) is a small specimen
which shows a change of slope in its late partand its ribs become more distinct with growth.
The small posterior ear is well preserved in thisspecimen.
The exceptional specimens mentioned above
are similar to, if not identical with, Inoceramus
waltersdorfensis hannovrensis Heinz, 1932
(Andert, 1934 (part), pI. 4, fig. 2; Troger, 1967,
p. 117, pI. 12, fig. 3; pI. 13, figs. 6-9; Kauffman,
1978a, pI. 5, figs. 3, 15; Kauffman, 1978b, pI.
2, figs. 2, 10; Kauffman in Herm et al., 1979,
p. 59, pI. 9, figs. D, G; Keller, 1982, p. 112, pI.
8, fig. 3). At least in our case, however, we think
it unnatural and unreasonable to separate a small
number of these exceptional specimens specifically from the coexisting more numerous,
normal specimens of Inoceramus rotundatus.
Occurrence:-Localities Ik 2716, Ik 2710, Ik
2714, Ik 2717, Ik 2726 [=2798] b, c and Ik
2786 [=2118], especially abundant at the firsttwo localities where fine-grained sandy siltstone
is exposed for about 15 m and 20 m in thickness, respectively. All in the lower part of theConiacian in the Pom bets-Gono-sawa [=Takiyoshi-zawa], Mikasa district, central Hokkaido.
Discussion and conclusion
Taxonomic position:-We regard the describedsample from the Pombets-Gono-sawa as representing a single species. The diagnosis has been
given on the basis of this sample. It conforms
generally with that of 1. rotundatus Fiege de-270

Tatsuro MATSUMOTO and Masayuki NODA

scribed by Trager (1967) and Keller (1982).
It is, however, troublesome for us to see
dissimilar expressions among authors (Fiege,
1930; Trager, 1967; Kauffman in Herm et at.,1979; Keller, 1982) about the specific characters.
For instance, Kauffman recognizes certain differences between left and right valves, but Keller
states as equivalve and Trager nearly equivalve.
Our observation on the Japanese forms conformwith Trager's in this respect. The diagram of thecross-section along the axis of growth illustratedby Trager (1967, fig. 29) shows a low breadthand generally gentle convexity of the valve,
but this may be probably due to the secondary
compression. Keller writes as "moderately
inflated" massig gewalbt). Our observation
generally conforms with Keller's, although we
recognize a considerable variation in the convexity of valve or b/h. Kauffman takes up achange of slope, or geniculation, of some valves
where there is also, according to him, a changeof ornamentation. Trager and Keller recognize
only a little or occasional geniculation. We
see also the geniculation in a. few specimensand generally a uniform or gradually changing
convexity predominates in our sample. The
observations on the ornamentation are notquite identical among authors either.
The characters shown by the populationof Pombets-Gono-sawa described in this paper
may not be quite identical with those shown by
the populations of the type and other placesin Germany. Similarly the populations in

Bohemia, Austria, England and the North American Western Interior Province may be somewhat dissimilar. At least some of the specimensfrom Hokkaido resemble closely the lectotype,and certain other examples of I. rotundatus
Fiege from Germany. Therefore, we would beallowed to identify our population with thatspecies. We could, however, expect a minor
difference - say on the average weaker, lessprominent concentric ribs in our form or generally smaller shell size in our sample than in
the lectotype and certain other illustrated
specimens from Germany. Whether this is distinctive enough for subspecific separation or
not is yet undetermined, unless the populations in Germany are carefully worked out tocompare with ours. In fact Keller mentions thevariability of the ornamentation and Kauffman(in Herm et at., 1979, p. 70) records the small
size of the Gosau specimens.
The relationship of Inoceramus rotundatus
Fiege with I. waltersdorfensis hannovrensis
Heinz is a problem. According to Keller (1982,
p. 116), the former is more strongly inflated
and has higher concentric ribs and a larger
angle (a) between the hinge-line and the anterior
margin than the latter. There is, however, variation in these characters and Keller himself
recognizes the presence of a transitional form
between the two species.
Dr. W. A. Cobban (in lit., April 27, 1984)
has kindly shown us an interesting plate on
which an intergrading sample (N ~ 28) of I.

Explanation of Plate 43
Figs. 1-11. Inoceramus totundatus Fiege(mostly small and presumably immature specimens)
1. GK. H10141 from loco Ik 2716d; right valve (a) and its anterior view (b), x 1.2. 2. JG.
H2867A from loco Ik 2716n; left valve (a) and its anterior view (b), x 1.8. 3. JG. H2858
from loco Ik 2716; left valve (a) and its anterior view (b), x 1. 4. GK. H10130 from loco Ik
2786 [=Ik 2118]; right valve, x 1.4. 5. GK. H10137 from loco Ik 2716q; left valve, x 2.
6. GK. H10140 from loco Ik 2716q; right valve, x 2. 7. JG. H2873 from loco Ik 2716; rightvalve, x 1. 8. JG. H2871A from loco Ik 2716; right valve, x 1.1. 9. JG. H2862 from loco Ik
27101; left valve (larger one), x 1. 10. JG. H2797 from loco Ik 2716n; right valves, A, B
and C from left to right, X 1.1. 11. GK. H10136 from loco Ik 2716q; left valve on the left,
xl.

MATSUMOTO and NODA: A Coniacian Inoceramid Species

Plate 43

806. A Coniacian Inoceramid Species
rotundatus and I. waltersdorfensis from one
locality (USGS Mesozoic locality 21421,
Montana, where associated fossils include
Scaphites meriasensis Cobban and early formsof S. preventricosus Cobban) is illustrated.
In the sample of the Pombets-Gono-sawa(Hokkaido), only a few specimens could be
identified with I. waltersdorfensis hannovrensis
but they are not separable from the more numerous normal forms of what we have identified
with I. rotundatus provisionally. In view of theweaker ribs on the average, our population of
I. rotundatus could be regarded as showing asomewhat transitional state from I. w. hannovrensis. In fact many specimens in our sample
resemble a form which Kauffman (197 Sa, pI.
5, fig. 16) illustrated under "I. wa?tersdorfensis
Andert, n. subsp. transitional to I. rotundatus",
but there are also some specimens which arecloser to the lectotype and certain other examples of 1. rotundatus from Germany. Clearly,
no specimen in our sample is identified with
1. waltersdorfensis waltersdorfensis Andert, 1911
itself (see Andert, 1934, p. 112, pI. 4, figs. 4-6;
Troger, 1967, p. 114, pI. 12, figs. 1, 2; pI. 13,
figs. 1-5).
To sum up, we think it better to call thestudied sample as Inoceramus rotundatus Fiege
and at the same time it should be noted thatsomewhat transitional feature between 1. waltersdorfensis hannovrensis Heinz and I. rotundatus
Fiege is shown by some specimens of our sample.
Biostratigraphic position:-There had been
discrepancy about the stage boundary andsubdivision of Turonian and Coniacian between
the scheme by German authors (before Seibertz,
1979) and the international one. Moreover,recent revisions do not seem to be quite identicalamong authors. We are afraid of this situationand should read carefully the relevant references.
Kauffman (in Herm et at., 1979) states thatI. waltersdorfensis waltersdorfensis is an excellent biostratigraphic index to the TuronianConiacian boundary zone. According to him,
its known range in the Western Interior of theUnited States is uppermost Turonian (top few
meters) and lowest Coniacian (basal 1-2 meters).

271

The age of I. rotundatus and I. waltersdorfensis hannovrensis was described as early
Coniacian by Kauffman (in Herm et al., 1979)
but late Turonian to early Coniacian by Keller(1982). Dr. Cobban has shown us anotherinteresting plate on which an assemblage of
specimens (N ~ 18) ranging in form from I.
waltersdorfensis through I. rotundatus to I.
erectus Meek is illustrated. They came fromone locality (USGS Mesozoic locality D11939,
Wyoming), where associated fossils include
Scaphites preventricosus. This ammonite andI. erectus are unmistakable Coniacian species
in North America.
We have not yet obtained any example ofI. erectus and I. waltersdorfensis waltersdorfensis from Hokkaido. I. rotundatus occurs
characteristically in the lower part of the tripartite scheme of Coniacin sequence along thePombets-Gono-sawa. Its associated fossils include
Forresteria(Reesideoceras)
petrocoriensis(Coquand), Harleites cf. H. harlei (Grossouvre),
Didymotis akamatsui (Yehara) and Inoceramus
uwajimensis Yehara. The last species is represented by a small number of atypical form in
the lower part and its typical form occurs abundantly in the middle part. 1. mihoensis Matsumoto, 1. (Cordiceramus) n. sp. and I. (Platyceramus) yubarensis Nagao et Matsumoto characterize the upper part. Therefore, we conclude
that 1. rotundatus would be a good subzonal
index to the Lower Coniacian in Hokkaido,
although the occurrence in other places should
be worked out.
Acknowledgments
We are much indebted to Messrs. Takemi
Takahashi, Shigehiro Uchida and Kikuwo Muramoto for their kind help in our field work. We
are also grateful to Dr. W. A. Cobban and Dr.
M. K. Hancock for their kind information onsome examples from North America and Europe.
Miss Yoshimi Tanigawa assisted us in preparing
the typescript.

Tatsuro MATSUMOTO and Masayuki NODA

272
References

Andert, H. (1911): Die Inoceramen der KreibitzZittauer Sandsteingebirges. Festschr. desHumboldtver. zur Feier seines 50 jahrigen
Bestehens, p. 33-64, 9 pIs., Ebersbach(inaccessible).
--(1934): Die Kreideablagerungen zwischen
Elbe und Jeschken, Teil III: Die Fauna derobersten Kreide in Sachsen, Bahmen undSchlesien. Abh. preuss. geol. Landesanst.,
N. F., Heft 159, p. 1-477, pIs. 1-19.
Brautigam, F. (1962): Zur Stratigraphie und
Palaontologie des Cenomans und Turons im
nordwestlichen Harzvorland. Diss. TH
Braunschweig, 261 p., 21 pIs. (inaccessible).
Cox, R. ~. (1969): Family Inoceramidae Giebel,
1852. In Moore, R. C. (ed.): Treatise on
invertebrate paleontology, Part N, Vol. 1,
Mollusca 6, Bivalvia. p. N314-N321. Geol.
Soc. Amer. & Univ. Kansas Press.
Fiege, K. (1930): tiber die Inoceramen desOberturon, mit besonderer Beriicksichtigung
der in Rheinland und Westfalen vorkommenden Formen. Palaeontographica, vol. 73,
p. 31-47, pIs. 5-8.
Hayamai, I. and Matsukuma, A. (1971): Mensuration of fossils and statistics - analysis ofallometry and variation -. Sci. Repts., Dept.
Geol., Kyushu Univ., vol. 10, no. 3, p. 135160 (in Japanese with English abstract).
Heinz, R. (1932): Zur Gliederung der sachsischschlesisch-bahmischen Kreide unter Zugrundelegung der norddeutschen Stratigraphie. 24 Jber. nieders. geol. Ver., p.

23-53, Hannover (inaccessible).
Herm, D., Kauffman, E. G. and Wiedmann, J.
(1979): The age and depositional environment of the "Gosau" Group (ConiacianSantonian),
Brandenberg/Tirol, Austria.

Mitt. Bayer. Staatsslg. Paliiont. hist. Geol.,
vol. 19, p. 27-92, pIs. 5-11.
Kauffman, E. G. (1978a): An outline of Middle
Cretaceous marine history and inoceramid
biostratigraphy in the" Bohemian basin,
Czechoslovakia. Ann. Mus. d 'Hist. nat. Nice,vol. 4 (for 1976), pt. 13, p. 1-12.
-(1978b): South African Middle Cretaceous
Inoceramidae. Ibid., vol. 4 (for 1976), pt.
17,p.1-6.
Keller, S. (1982): Die Oberkreide der SackMulde bei Alfeld (Cenoman-Unter-Coniac).
Lithologie, Biostratigraphie und Inoceramen.
Geol. Jahrb., Reihe A, Heft 64, p. 3-171,
pIs. 1-8.
Matsumoto, T. (1984): The so-called TuronianConiacian boundary in Japan. Bull. Geol.
Soc. Denmark, vol. 33, p. 171-18I.
Seibertz, E. (1979): Problem der Turon-Gliederung nordeuropas (Oberkreide) im Uberregionalen Vergleich. Newsl. Stratigr., vol.
7, p. 166-170.
Trager, K. A. (1967): Zur Paliiontologie, Biostratigraphie und faziellen Ausbildung derunteren Oberkreide (Cenoman bis Turon).
Teil I: Paliiontologie und Biostratigraphie
der Inoceramen des Cenomans bis Turons
Mitteleuropas. Abh. Staatl. Mus. Mineral.
Geol., vol. 12, p. 13-207 (incl. 14 pIs.).

Explanation of Plate 44
Figs. 1-8. Inoceramus rotundatus Fiege(small, probably immature specimens, sometimes with the adult)
1. JG. H2870 (left valve), x 1; 2. GK. H10141 (left valve), xLI; 3. JG. H2867, x 1.2;
1-3 all from loco Ik 2716n. 4. JG. H2901 from loco Ik 2716d; right valve, x 1. 5. GK.
H10138-10139 from loco Ik 2716q, x 2. 6. JG H2874 from loco Ik 2710k, xL 7a, b. JG.
H2896 from loco Ik 2716q; x 1. 8. GK. H10133 from loco Ik 2716q, x 1 (see also PI. 42,
Figs. 5a, b).

MA TSUMOTO and NODA: A Coniacian Inoceramid Species

Plate 44

806. A Coniacian Inoceramid Species

Mikasa =~Pombets-Gono-sawa 9IJiZ1J1L/ ~Takiyoshi-zawa ~i!f~~tifii)]i:Q)::l .=. 7 -/7:/ rtmi¥: -{ / ~ 7.to.;r.Q) 1 fil::'-?I,,-C:~tifii)]i:=~it!!~Q)~~IJ1L/~ (~i!fiR.) 1::.1i!±:li"~J:tmBBI!*Q)iI!5E~.ht.:tm7hH-,. ~**~iJ>l?lt*;;oQ)-{ / ~ 7.to.
;r.~*~1H!!:tI<~ Lt.:. .:. .hIt r -{ 'l.:t: Q)f1t!iJ> I? gEi" ~ Inoceranus .rotundatlls Fiege I::./m
5E"C'~~. f:w.:ffQ) J: 1,'2500{;!>:I::'-?I,'-Clt~tiJIlj L. ki1f~t((.JI::.{i:fk~~14~~"-c~*tLt.:. r-{'l gEQ)JI!1.1~!.I¥]Q) t Q)t::.lt~i" ~ c!::JI1JQ)~I,' t Q)tJ~~I"tJ~. ~m~*tJ:.l,..Q) 1(:, ~~. I. rotunI. waltersdorfensis hannovrensis Heinz cQ)*~t.l:~tf-ltifi~~"C':b~lOl?n-CI,'
datus~iJ~. ~tifii)]i:Q) t Q) It I, , I?tJ> <pre'B~ Q) i1::tt~7f, Lt.: iJ~1? 1(:, l-?Q) fiHt~ L. .:t:.hlt I.
rotundatus t::./m5Ei" ~ Q)iJ~~~"C'~~. *.fIlt.:. Q)iR.lfh'Q)/ij/fl::':J\jI,'-C::l .=. 7 -/7:/z. 3c<7t Lt.:rtml::'~~I¥.J"C'. f*? 7 :/"'3: -;- -{ .. 1(:, l5.J~r$~7f,i". =~!t!!IK"C'lt 1 ~*Q)7f,i\!!{t.;o"C'.:i; IJ. OO~%t.ltJ:. t ~~tJ:~"C'~~.
t~*i!f!~ • ffeafltz.

Postscript. In August 1985, prior to the proof reading, one of us (T.M.) reexamined
the outcrop of loco Ik 2710, with a result that the form of moderate size anddistinct ribbing, as represented by JG. H 2860 (PI. 41, Fig. 4), predominates in theupper part of the exposed sequence.

273

274

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Transactions and Proceedings of the PalaeontologicalSociety of Japan
New Series No. 140

December 30, 1985

CONTENTS
TRANSACTIONS
804. MATSUI Seiichiro: Recurrent molluscan associations of the Omma-Manganji faunain the Gojome-Oga area, Northeast Honshu. Part 2. Systematic notes onbibalve species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
805. MATSUOKA Kazumi: Cyst and thecate forms of Pyrophacus steinii (Schiller) Wallet Dale, 1971 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
806. MATSUMOTO Tatsuro and NODA Masayuki: A note on an inoceramid species(Bivalvia) from the Lower Coniacian (Cretaceous) of Hokkaido ........... 263