DULAI, A. (2001): Middle Miocene (Badenian) Polyplacophora (Mollusca) remains from borehole Szokolya-2 (Börzsöny Mts, Hungary, Central Paratethys). - Fragmenta Palaeontologica Hungarica

Middle Miocene (Badenian) Polyplacophora (Mollusca) remains from borehole Szokolya-2 (Börzsöny Mts, Hungary, Central Paratethys)

by A l f r é d D L L A I

Abstract — Polyplacophora valves are hardly known from Hungarian Miocene deposits. Recently, small polyplacophorans were found in the Badenian (Middle Miocene) small-sized grey marly sandstones at the southern part of the Börzsöny Mts (North Hungary, borehole Szokolya-2). Five determinable specimens refer to a very diverse fauna: Lepidochitona lepida (REUSS), Acanthocbitona faluniensis (ROCHEBRUNE), Cryptoplax weinlandi SULC, Cryptoplax margitae n. sp. With the exception of the new species, the other three ones belong to the most frequent Miocene Polyplacophora remains of the Central Paratethys (they are also common in the Korytnica Basin, Vienna Basin and Transylvanian Basin). The accompanying fauna contains diverse mollusc and bryozoa remains.

Keywords — Polyplacophora, Middle Miocene, Badenian, Hungary, Central Paratethys, new species, Lepidochitona, Acanthocbitona, Cryptoplax

DULAI, A. (2001): Middle Miocene (Badenian) Polyplacophora (Mollusca) remains from borehole Szokolya-2 (Börzsöny Mts, Hungary, Central Paratethys). — Fragmenta Palaeontologica Hungarica, 19: 39-49.

Introduction

The Miocene sedimentary formations of Hungary are very rich in fossils, including the diverse forms o f molluscs. However, the different classes of molluscs are represented at very different rates. Gastropods and bivalves are very abundant, but at the same time polyplacophorans are rather rare. A single locality is known in the Hungarian palaeontological literature (Hidas, Mecsek Mts, South Hungary) from where Chiton lepidus (REUSS) and Chiton denudatus (REUSS) were mentioned without any kind of illustrations (PETERS 1861; STRAUSZ 1928; CSEPREGHY-MEZNERICS 1950).

In addition S T U D E N C K A & S T U D E N C K I (1988)

mentioned the presence of Lepidochitona (Lepidochitona) subgranosa B A L U K and Acanthocbitona faluniensis ( R O C H E B R U N E ) in the Lower Badenian sand of Várpalota (Bakony Mts, Transdanubian Central Range) (on the basis of a material deposited in the Museum of the Earth in Warszawa, collected by G. Jakubowski).

Fossil chitons are similarly rare in the other areas of the Paratethys and they have so far been described from only a few localities. B A L U K (1971) mentioned two possible reasons of this relative scarcity. First of all, their occurrences are generally limited to nearshore zones, and secondly, after the death of the animal the shells are disintegrated in separate, small-sized valves. We may add, that the rarity o f hard rocky substrates in the vicinity of deposition o f most fossiliferous sediments might well contribute to the scarcity o f chitons in the fossil record.

Relatively abundant chiton assemblages are known in Korytnica Basin, Vienna Basin and Transylvanian Basin of the Central Paratethys. The most diverse Polyplacophora fauna of the European Miocene deposits is known from southern Poland: B A L U K (1971, 1984) described 18 species from the Badenian (Middle Miocene) Korytnica Clays (Holy Cross Mts; Góry

Swietokrzyskie). Chitons o f the Vienna Basin were described by REUSS (1860) and SULC (1934). Polyplaco­phorans were mentioned from the Transylvanian Basin by BOETTGER (1896) and ZlLCH (1934), mainly from the famous Costei (Kostej) and Läpugiu (Lapugy) localities. The Miocene Polyplacophora literature o f the other European areas was summarized by BALUK (1971).

The polyplacophorans, commonly known as chitons, are slow-moving, bilaterally symmetrical, marine molluscs. They are dorso-ventrally flattened, oval to elongate molluscs, characterised by 8 dorsal, articulating valves. The polyplacophoran shell is composed o f aragonite and the individual valves have four or five layers. The shell valves contain unique microscopic structures called aesthetes, which appear to have both sensory and secretory functions. The valves are embedded in a fleshy, muscular girdle, which enables the animal to closely follow the topography o f the substrate as it moves. The ventral surface is dominated by the large creeping foot. Anterior to the foot is the simple head, which bears the mouth but lacks eyes or tentacles. The mouth bears a large, well-developed toothed structure, the radula, which contains rows o f 17 teeth. Chitons have separate sexes, but lack any sexual dimorphism. They usually lay eggs and these develop via a short-lived larval stage, but several species are known to brood their eggs in the palliai groove.

Polyplacophorans are typically grazers, living attached to rocky substrates in the intertidal and shallow sublittoral coastal regions, although some groups are known to occur in deep water down to 5000 m. Chitons mainly live on or under rocks and some can tolerate silt and soft bottoms. Herbivores feed on marine algae, while omnivores may have a varied diet ranging from

young barnacles to hydroids and bryozoans. Algae are removed from rocky surfaces by the rasping action o f the radula. Polyplacophorans range in size from only a few mm long to some 10 cm. They are an ancient

group, isolated valves having been found in the Upper Cambrian, but the fossil record is generally poor. At present there are some 10 families and about 750 living species in the seas.

Locality

Figure 1 — Sketch map showing the location of borehole Szokolya-2.

Hungary and the Carpathian Basin belonged to the Central Paratethys during the Miocene period, therefore a significant part o f the basin contains marine Miocene formations. The Börzsöny Mountains are situated at the northern border o f Hungary, at the westernmost part o f the so-called Inner Carpathian Neogene to Pleistocene calc-alkaline Volcanic Chain. The basement consists o f carbonate rocks related to the Transdanubian Central Range to the south and crystalline schists o f the Veporides to the north, separated by the Diósjenő line. These formations are overlain mostiy by Ol igocène and

Lower Miocene sedimentary rocks. The main mass o f

the mountains consists of andesitic-dacitic volcanic

rocks, which are 1000 m thick at some places.

According to BÁLDI & KÓKAY (1970) the volcanic

formations developed in the Early Badenian during a

relatively short time. Recendy, KARÁTSON et al. (2000)

summarized the volcanic evolution of the Börzsöny Mts

and they postulated a longer interval than BÁLDI &

KÓKAY (1970) for the volcanic activity. The volcanic

rocks are overlain by early Badenian Leitha Limestone

and some other sedimentary rocks, including the

examined sandy marls and marly sandstones at

Szokolya. These sedimentary formations are situated

mainly along the western and southern margin of the

mountains.

Several drillings were made in the examined area

during the geological mapping o f the Börzsöny Mts in

the years around 1970. The borehole Szokolya-2 was

made in 1971 (Figure 1). The simplified sequence of the

borehole is the following (all formations are Badenian in

age) (Figure 2):

Figure 2 — Simplified sequence of borehole Szokolya-2 (modofied after B O H N - H A V A S 1972). 1 - soil and scree; 2 -limestone; 3 — sand, sandstone; 4 — marl; 5 - clay; 6 — andésite; 7 — location of Polyplacophora valves.

0—2.8 m: soil and scree

2.8—5.4 m: yellowish grey limestone, sandy limestone

5.4—9.6 m: yellowish grey calcareous sandstone

9.6—16.5 m: yellowish grey sandy marl

16.5—38.3 m: yellowish grey sandstone

38.3—76.7 m: grey sandy marl

Middle Miocene (Badenian) Polyplacophora from Szokolya 41

76.7-91.1 m: grey clayey marl 111 .2-115.3 m: grey marly clay 91.1-102.2 m: grey marly sandstone 115.3-118.3 m: grey sandy marl 102.2-104.7 m: grey sandy clay 118.3-120 m: limestone 104.7-111.2 m: grey marly sandstone 120-140 m: andésite

Material

The fine, small-sized sandy marls and marly sandstones are full of fossils. The most diverse group is the molluscs, including lots o f micromolluscs. The dominant fossils are gastropods and bivalves, but several other groups are also represented in the accompanying fauna (including bryozoans, decapods, otoliths, etc.). The polyplacophorans are accessorical elements. Five determinable specimens were found: four of them from 92.7-93 m interval and one specimen from 109-111.2 m interval. The accompanying fauna contains diverse mollusc and bryozoan remains. The bivalves (Myrtea spinifera M O N T A G U , Venus sp., Corbula sp.) belong to the suspension feeding infauna. The gastropods contain browsing (Alvania partschi HÖRNES, Cerithiella kostejana BOETTGER, Rissoa acuticosta SACCO),

carnivore (Hinia hoernesi MAYER) and ectoparasite (Odostomia sp., Pyramidella sp.) epifaunal elements. The bryozoan fauna consists of lunulitiform (Cupuladria cavernosa CADÉE, Lunulites androsaces M A N Z O N I ) and cellariiform (Cellaria salicornioides LAMOUROUX, Pleuronea pertusa (REUSS), Escharoides coccinea (ABILGAARDJ, Calpensia sp., Canda sp.) elements.

The chitons were examined by scanning electron microscopy at the Scanning Laboratory of Hungarian Geological Institute. The specimens are deposited in the collection of the Department of Geology and Palaeontology of the Hungarian Natural History Museum, Budapest (inventory numbers: M.99.109— M.99.113).

Systematics

Phylum Mollusca Class Polyplacophora DE BLAINVILLE, 1816 Order Ischnochitonida BERGENHAYN, 1930

Family Ischnochitonidae D A L L , 1889 Genus Lepidochitona GRAY, 1821

Lepidochitona lepida (REUSS, 1860) (Plate I : 1-6)

1860 Chiton kpidus n. sp. — REUSS, p. 259, pi. 8, figs. 12-13. 1897 Lepidopleurus cf. marginatus (PENN.) — SACCO, p. 90, pi. 7, fig. 32. 1934 Middendorfta lepida (REUSS) — §ULC, pp. 10-11, pl. 1, figs. 13-15. 1950 Chiton lepidus REUSS — CSEPREGHY-MEZNERICS, p. 15. 1971 Lepidochitona lepida (REUSS) — BALUK, pp. 459^60, pi. 4, figs. 6-12. 1984 Lepidochitona lepida (REUSS) — BALUK, pp. 288-289, pi. 7, figs. 1-3. 1988 Lepidochitona (Lepidochitona) lepida (REUSS) — SlUDENCKA & S T U D E N C K I , pp. 39-40, pi. 2, figs. 1 and 3. 1988 Lepidochitona lepida (REUSS) — MACIOSZCZYK, p. 53.

Material — 2 intermediate valves (borehole Szokolya-2, 92.7-93 m and 109-111.2 m) (M.99.109 and M.99.110).

Measurements (mm): length width M.99.109 1.3 2.46 M.99.110 1.26 1.76 (fragmentary)

Description — The valves are broad. Fine granules ornament the surface of the entire tegmentum. The flattened oval granules are regularly distributed, forming two intersecting systems of rows on the first specimen (Pl I : 1—3). The granules are arranged in longitudinal rows on the jugal areas and in roughly radiated transversal rows on the lateral areas on the second specimen (Pl I : 4—6). The lateral areas are marked by a slight ridge. On the lateral areas the nodes are closely spaced, arranged one near another, but they are rarer on jugal areas. Sutural plates are wide and rounded. There are several pores on the nodes and along the nodes.

There is a larger sized pore at the centre of the nodes, and there are several (7-10) smaller ones around the central pore.

Remarks — Although one o f the specimens is a fragmentary intermediate valve, both of them well correspond with the published specimens (see SULC 1934, pi. 1, fig. 14; B A L U K 1971, pi. 4, figs. 7., 9 and 10; B A L U K 1984, pi. 7, fig 2). The specimens previously determined under the name of Lepidochitona lepida (REUSS) were interpreted as Lepidochitona dnerea (LINNAEUS) or Middendorfta caprearum (SCACCHI) by

LAGHI (1977). However, the detailed studies on the recent Lepidochitona dnerea (LINNAEUS) by K A A S & V A N B E L L E

(1981) showed the characteristic differences between the fossil and the recent species (see details at STUDENCKA & STUDENCKI 1988). Middendorßa caprearum (SCACCHI) was synonymyzed with Lepidochitona corrugata (REEVE) by K A A S & V A N B E L L E (1981). This present-day species can also be separated from Lepidochitona lepida (REUSS), but the high degree of similarity refer to a close relationship between the two species (see M A L A T E S T A 1962; STUDENCKA &

S T U D E N C K I 1988). The determination of the fossil species within the genus Lepidochitona is highly problematic. In the case of isolated, (sometimes fragmentary) fossilized valves, it

is almost impossible compare with the recent species. Therefore, the two Hungarian specimens are included into the fossil species established by REUSS, as other authors in the case of Middle Mocene specimens of Austria, Poland and Romania also did i t

Distribution — This species has hitherto been known from the Czech Republic (Rudoltice: REUSS 1860, SULC 1934); Romania, Transylvania (Costei and Lápugiu: SULC 1934); Hungary (Hidas: CSEPREGHY-MEZNERICS 1950); Italy (SACCO 1897) and Poland (Korytnica: BALUK 1971, 1984; Nawodzice and Rybnica: STUDENCKA & STUDENCKI 1988; Weglinek and Weglin: MACIOSZCZYK1988).

Order Acanthochitonida BERGENHAYN, 1930 Family Acanthochitonidae PlLSBRY, 1893

Genus Acanthocbitona GRAY, 1821

Acanthochitona faluniensis ( R O C H E B R U N E , 1883) (Plate I I : 1-3)

1860 Chiton (Acantbochites) fasäcularis L. var. — REUSS, pp. 260-261, pi. 8, figs. 4-6. 1883 Acantbochites Faluniensis ROCHEBRUNE — ROCHEBRUNE, pp. 60-61. 1934 Acanthochiton faluniensis ROCHEBRUNE — S>ULC, pp. 17-18, pl. 1, fig. 29; pi. 2, figs. 30-32. 1971 Acanthochitona faluniensis (ROCHEBRUNE) — BALUK, pp. 463-464, pi. 2, figs. 10-15. 1984 Acanthochitona faluniensis (ROCHEBRUNE) — BALUK, pp. 291-292, pi. 8, figs. 1-5. 1988 Acanthochitona faluniensis (ROCHEBRUNE) — STUDENCKA & STUDENCKI, p. 41, pi. 4, fig. 3. 1988 Acanthochitonafalunensis (ROCHEBRUNE) — MACIOSZCZYK, p. 55, pi. 3, figs. 8-9.

Material — One head valve (borehole Szokolya-2, 92.7-93 m) (M.99.111).

Measurements (mm): length width M.99.111 1.38 2.1

Description — The relatively thick valve is ornamented by closely spaced nodes. The nodes are low, dorsally flattened and round in outline. The arrangement of the nodes is irregular. Two or three pores can be seen on each nodes. The apex region of the head valve is smooth, without any nodes, but with some pores. The insertion plate of the head valve is cut by six slits, in the extension of which there are shallow grooves not reaching the boundary of the tegmentum.

Remarks — The only head valve well corresponds to the published specimens from the Vienna and Korytnica Basin (see SULC 1934, pi. 2, fig. 32; BALUK 1971, pi. 2, figs. 10-11; B A L U K 1984, pi. 8, figs. 1-2.). The Pseudoacanthochiton subgenus, established by SULC (1934) has been synonymized with Acanthochitona GRAY by SMITH (1960). L A G H I (1977) postulated that both the Korytnica specimens and the Vienna Basin specimens are conspecific with the Recent Acanthochitona communis (RlSSO). This statement was rejected by BALUK (1984), STUDENCKA & STUDENCKI (1988) and

MACIOSZCZYK (1988) because the shape of the tegmentum of the intermediate and tail valves is cleady different at the two species. The Hungarian specimen has six slits on the insertion plate of the head valve, while BALUK (1971) mentioned 5 slits at the Korytnica specimens.

Distribution — This species is very frequent in the Central Paratethys. I t was mentioned from several localities of the Vienna Basin, Bohemia and Transylvania (Kaiinice, Rudoltice, Steinabrunn, Coçtei and Lápugiu; SULC 1934). The remains of this species can be found at several localities in Poland (Korytnica: BALUK 1971, 1984; Nawodzice and Rybnica: STUDENCKA & STUDENCKI 1988; Monastyrz and Miasteczko: JAKUBOWSKI & MUSIAL 1977; Trzesiny: JAKUBOWSKI & MUSIAL 1979; Wçglinek, Wçglin and Lychów. MACIOSZCZYK 1988). Acanthochitona faluniensis (ROCHEBRUNE) was also mentioned from Várpalota (Hungary) by STUDENCKA & STUDENCKI (1988).

Explanation to Plate I

1-3 Lepidochitona lepida (REUSS, 1860); intermediate valve; Szokolya-2,109-111.2 m; M.99.109. — 1: dorsal view, x 30; 2: dorsal view (detail of Plate I : 1), x 300; 3: dorsal view (detail of Plate I : 2), x 600.

4-6 Lepidochitona lepida (REUSS, 1860); intermediate valve; Szokolya-2, 92.7-93 m; M.99.110. — 4: dorsal view, x 39; 5: dorsal view (detail of Pl. I : 4), x 300; 6: dorsal view (detail of Plate I : 5), x 1200.

Genus Cryptoplax de BLAINVILLE, 1818 Cryptoplax weinlandiSULC, 1934

(Plate I I : 4-6, Plate I I I : 1-6)

1896 Cryptoplax weinlandi (ROLLE) — BOETTGER, p. 180. 1934 Cryptoplax weinlandi (ROLLE) SULC — ŐULC, pp. 21-23, pi. 2, figs. 36-40. 1934 Cryptoplax weinlandi SULC — ZlLCH, pp. 199-200, pl. 1, figs. 18-22. 1964 Cryptoplax weinlandi SuLC — MARINESCU, pp. 183-184, pi. 4, figs. a-e. 1971 Cryptoplax weinlandi SULC — BALUK, p. 466, pi. 6, figs. 1-8. 1977 Cryptoplax weinlandi SULC — LAGHI, p. 114. 1984 Cryptoplax weinlandi SULC — BALUK, p. 294.

Material — A single tail valve (pl. I I I . figs 1-6) (borehole Szokolya-2, 92.7-93) (M.99.112).

Measurements (mm): length width M.99.112 2.4 1.26

Descriptions — The jugal area of the tail valve is smooth while the lateral areas are ornamented by a few (4-^4) longitudinal, slighdy undulate ribs. Both the jugal area and the lateral areas bear lots o f small pores. Small pores can also be seen on the ventral surface o f the tail valve, but only at the jugal area. The pores are round in outline at both sides of the valve. The apex of the only valve is covered by epizoans. The length of suturai plates of the tail valve is about 1 /2 o f the whole length of the valve.

Remarks — The only Hungarian specimen correspond well both with the illustrations given in the literature and the Transylvanian specimens deposited in the collection of Hungarian Natural History Museum. I t was indicated by B A L U K (1971) that Cryptoplax genus is unknown in recent European seas and it was regarded as typical of the Indo-Pacific regions. However, L E L O U P (1980) described a new species, Cryptoplax enigmathus L E L O U P from the Red Sea, which differs from Cryptoplax wdnlandi SULC in a smaller size and in

the granulated ribs on the lateral areas. A n intermediate valve o f C. weinlandi SULC from the Transylvanian material of the Hungarian Natural History Museum is given at Plate I I : 4—6 as comparative material.

Distribution — This species has hitherto been mentioned from several localities o f the Central Paratethys. SULC (1934) described i t from the Vienna Basin and Bohemia (Steinabrunn, Niederleis, Forchtenau, Porzteich, Rudoltice, Kninice, Sudice, Borac, Zidlochovice, Lysice localities). This species is well-known in Romania, both from the Transylvanian Basin (BOETTGER 1896, ZlLCH 1934) and the Dacian Basin (MARINESCU 1964). Cryptoplax weinlandi SULC is also abundant in the Korytnica Basin in Poland (BALUK 1971, 1984). I t was also mentioned from the Miocene deposits exposed near Modena, Italy (LAGHI, 1977). I t is one o f the most frequent Miocene chitons of the Central Paratethys, particularly well represented at Läpugiu and Costei (ZlLCH 1934).

Cryptoplax margitae n. sp. (Plate IV: 1-6)

Holotype — Hungarian Natural History Museum, Department o f Geology and Paleontology; inventory number: M.99.113.

Type locality — borehole Szokolya-2, 92.7-93 m; Börzsöny Mts, Hungary, Central Paratethys. Type strata — Badenian (Middle Miocene) marly sandstone. Derivation of name — after the name of Dr. Margit BOHN—HAVAS, retired paleontologist o f the Hungarian

Geological Institute. Diagnosis — Small-sized Cryptoplax with 5-5 granulated ribs on the lateral areas o f the intermediate valve. Short

suturai plates on the intermediate valve. Oval pores at the ventral side of the jugal area of the intermediate valve. Material — One intermediate valve (borehole Szokolya-2, 92.7-93 m).

Measurements (mm): length width M.99.113 2.86 1.16

1-3

4-6

Explanation to Plate I I

Acanthochitona faluniensis (ROCHEBRUNE, 1883); head valve; Szokolya-2, 92.7-93 m; M.99.111. — 1: dorsal view, x 39; 2: dorsal view (detail of Plate I I : 1), x 100; 3: dorsal view (detail of Plate I I : 2), x 300.

Cryptoplax weinlandi §ULC, 1934; intermediate valve; Kostej, M.60.10797. — 4: dorsal view, x 20; 5: dorsal view

(detail of Plate I I : 4), x 300; 6: dorsal view (detail of Plate I I : 5); x 1000.

Fragmenta Palaeontologica Hungarica 19, 2001

DULAI, A.

Plate I I I

Description — The jugal area o f the intermediate

valve is smooth while the lateral areas are ornamented

by 5-5 longitudinal, granulated ribs. The edges o f the

jugal area are slighdy undulated. Both the jugal area and

the lateral areas bear lots o f small pores. The pores are

irregularly arranged at the jugal area, and they are

situated at the centre of the granulations at the lateral

areas. Small pores can also be seen on the inner surface

of the intermediate valve, but only at the jugal area. The

pores are oval in outline at the inner side o f the valve.

The apex of the only valve is ended in about 120° angle.

The length o f the suturai plates of the intermediate

valve is about 1 / 4 o f the whole length of the valve.

Remarks — This specimen definitely differs from

the widespread European Miocene species, Cryptoplax

weinlandi SULC. The new species has a smaller size and

granulated ribs on the lateral areas. The pores are oval in

outline at the inner side of the valve, while rounded in

outline at Cryptoplax weinlandi SULC. I t is more similar to

the recent Cryptoplax enigmaticus described by L E L O U P

(1980), that has 4—6 granulated ribs on the lateral areas.

However, there is a significant difference in the length

of the suturai plates. I t is about half o f the whole length

of the valve at the recent species, while hardly 1/4 at the

Miocene species. There is no indication about the pores

in the description o f Cryptoplax enigmaticus L E L O U P ,

which probably refers to another significant difference

between the two species.

Distribution — Up to now, this species is known

only from the Hungarian Miocene.

ACKNOWLEDGEMENTS — This study was supported by the Hungarian Scientific Research Fund (OTKA F 13975). Many thanks are due to Dr. Margit BOHN-HAVAS for the samples of borehole Szokolya-2. The SEM photos were taken in the SEM Laboratory of the Hungarian Geological Institute by Mrs. TAKÁCS and Mrs. PELLÉRDY. I wish to thank Pál MÜLLER (Hungarian Geological Institute) and Miklós MONOSTORI (Eötvös University) who reviewed the manuscript of this paper and contributed to its improvement.

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SMITH, A. G. (1960): Amphineura. — In: MOORE, R. C. (editor): Treatise on Invertebrate Paleontology, Part I (Mollusca 1). — 141—176, Lawrence, Kansas.

Explanation to Plate I I I

1-6 Cryptoplax weinlandi SULC, 1934; tail valve; Szokolya-2, 92.7-93; M.99.112. — 1: dorsal view, x 30; 2: ventral view,

x 30; 3: ventral view (detail of Plate I I I : 2), x 80; 4: frontal view, x 55; 5: dorsal view (detail of Plate I I I : 1), x 300; 6:

ventral view (detail of Plate I I I : 3), x 500.

STUDENCKA, B. & STUDENCKI, W. (1988): Polyplacophora from the Gebieten. —Annalen des Naturhistorischen Museums in Wien, 47: 1-Badenian (Middle Miocene) marine sandy facies of the Holy 31. Cross Mts (Central Poland). — Trace Museum Ziemi, 40: 37-46. ZlLCH, A. (1934): Zur Fauna des Mittel-Miocäns von Kostej (Bánat).

SuLC, J. (1934): Studie über die fossilen Chitonen. I - Die fossilen —Senckenbergiana 16 (4-6): 193-302. Chitonen in Neogen des Wiener Beckens und angrezenden

Author's address: Dr. Alfréd D U L A I Geological and Palaeontological Department Hungarian Natural History Museum Múzeum krt. 14—16. 1431 Budapest, Pf. 137 Hungary E-mail: [email protected]

Explanation to Plate I V

1-6 Cryptoplax margitae n. sp.; intermediate valve; Szokolya-2, 92,7—93; M.99.113. — 1: dorsal view, x 30; 2: ventral view (detail of Plate IV: 1), x 30; 3: dorsal view, x 400; 4: dorsal view (detail of Plate IV: 1), x 300; 5: dorsal view (detail of Plate IV: 1), x 300; 6: ventral view (detail of Plate IV: 2), x 200.