NORSK GEOLOGISK TIDSSKRIFT 43 THE MIDDLE ORDOVICIAN OF THE OSLO REGION, NORWAY 15. Monoplacophora and Gastropoda By ELLIS L. Y OCHELSON (Present address: U.S. Geological Survey, Washington 25, D.C., U.S.A.) With 8 plates. Abst rac t. The Middle Ordovician gastropods described by Koken in 1889, 1897 and 1925 are redescribed and reillustrated. Approximately six hundred fifty specimens, including the types, are available from units 4a and 4b. Most specimens are not specifically identifiable; within same superfamilies, many specimens are generically indeterminate. Because well preserved specimens are rare, an apen nomenclature has been employed for most new taxa. The fauna of 4b is slightly more diversified than that of 4a, but both faunas are limited to few species. The preponderant number of specimens come from limestone masses within dark shale. This is considered to be an allocthonous occurrence. Few specimens come from shallow water deposits peripheral to and overlying the dark shales. The faunas of these two facies is different, but the second is so poorly known that no dose comparisons can be made. Several of the forms in the shallow water assemblage are known from single specimens. Less than a dozen specimens of monoplacophorans are known. Pollicina conoidea is transferred to Hypseloconus ?. Palaeoscurria ( ?) norvegica is trans­ ferred to Archinacella. One new species, Archinacella stoermeri, is described. Lepetopsis inopinata may be an inarticulate brachiopod. The gastropod fauna is composed almost entirely of Archaeogastropoda with Bellerophontacea and Pleurotomariacea constituting the majority of the taxa. Three specimens of Archaeogastropoda? representing three genera are known. Only one caenogastropod is known. In summary of the gastropod taxonomy, twenty-six genera are recognized in the Middle Ordovician of Norway, but only twenty-two genera can be named; three are indeterminate and the fourth is based on a nomen dubium. Three new 134 ELLIS L. YOCHELSON species are described and named. These are Omospira? holtedahli, lvlourlonia mjoesa and Holopea henningsmoeni. Four new species are described but not named and ten species, including two from undetermined genera, are described or discussed informally. One species is only tentatively identified and is not described and another is well known and again not described. Five species are in their originally described generic taxon. Twelve species are transferred to other generic taxa. Five specific names based on Norwegian type specimens have been placed in synonymy. CONTENTS Abstract . 133 Introduction and acknowledgements 137 Previous study . 138 Method of study . 140 Distribution and preservation of the gastropod fauna . 142 Ecological considerations . 144 Systematic paleontology . 147 Class Monoplacophora \\!enz in Knight, 1952. 147 Order Archinacelloidea Knight and Y ochelson, 1958. 147 Superfamily Archinacellacea Knight, 1956. 147 Family Archinacellidae Knight, 1956. 147 Genus A rchinacella Ulrich and Scofield, 1897. 147 A rchinacella norwegica (Ferner, 1925). 147 A rchinacella stoermeri Y ochelson, new species. 148 Archinacella species . 149 Family Hypseloconidae Knight, 1956 . 149 Genus Hypseloconus Berkey, 1898 149 Hypseloconus? conoidea (Koken, 1925) . 149 Addendum to Monoplacophora ... 150 Class Gastropoda Cuvier, 1797 . 151 Subclass Prosobranchia Milne-Edwards, 1848 151 Order Archaeogastropoda Thiele, 1925 151 Suborder Bellerophontina Cox and Knight, 1960 151 Superfamily Bellerophontacea M'Coy, 1851 . 151 Family Sinuitidae Dall in Zittel-Eastman, 1913 151 Subfamily Bucanellinae Koken, 1925 . 151 Genus Pharetrolites Wenz, 1943 . 151 Pharetrolites ? tumidus (Koken, 1897) 151 Pharetrolites ? elegans (Koken, 1925) 153 Subfamily Sinuitinae Dall in Zittel-Eastman, 1913 154 Genus Sinuites Koken, 1896 . 154 Subgenus Sinuites Koken, 1896 . 154 Sinuites (Sinuites) niger Koken, 1897. 154 Sinuites (Sinuites) corpulentus Koken, 1925 156 MONOPLACOPHORA AND GASTROPODA 135 Family Bellerophontidae M'Coy, 1851 . 158 Subfamily Tropidodiscinae Knight, 1956. 158 Genus Tropidodiscus Meek and \,Yorthen, 1866. 158 Tropidodiscus sphenonotus (Koken, 1897) . 158 Tropidodiscus? ogygiae (Koken, 1925) . 161 Genus Phragmolites Conrad, 1838 . 162 Phragmolites? reticulata (Koken, 1896) 162 Subfamily Bucaniinae Ulrich and Scofield, 1897. 164 Tribe Bucaniides Ulrich and Scofield, 1897. 164 Genus Bucania Hall, 1847 . 164 Bucania? christianiae (Koken, 1925) 164 Genus Kokenospira Bassler, 1915 . 166 Kokenospira esthona (Koken, 1889) . 166 Kokenospira insularis (Koken, 1925) 168 Kokenospira new species . 171 Subfamily Bellerophontinae l\I'Coy, 1851 17 3 Genus Cymbularia Koken, 1896 . 173 Cymbularia pygmaea Koken, 1925 173 Cymbularia species . 17 5 Suborder Macluritina Cox and Knight, 1960 . 175 Superfamily Euomphalacea de Koninck, 1881 17 5 Family Helicotomidae Wenz, 1938 . 175 Genus Helicotoma Salter, 1859 . 17 5 Helicotoma? norvegica (Koken, 1925) 175 Helicotoma new species 176 H elicotoma? new species . 17 S Family Euomphalidae de Koninck, 1881. 179 Genus Lytospira Koken, 1896. 179 Lytospira norvegica Koken, 1925 179 Lytospira species . Hll Genus Ecculiomphalus Portlock, 1843 181 Ecculinomphalus cf. E. princeps (Remele, 1888) ISJ Ecculiomphalus ? species . 184 Genus Lesueurilla Koken, 1898 . 184 Lesueurilla dilata (Koken, 1925) . 184 Suborder Pleurotomariina Cox ;cmd Knight, 1960 1S5 Superfamily Pleurotomariacea Swainson, 1840 185 Family Raphistomatidae Koken, 1896. 185 Subfamily Ophiletinae Knight, 1956 . 1S5 Genus Pararaphistoma Vostokova, 1955 185 Subgenus Pararaphistoma (Pararaphistoma) Vostokova 1955 . 185 Pararaphistoma (Pararaphistoma) schmidti (Koken, 1889) . 1S5 Pararaphistoma (Pararaphistoma) bipatellare (Koken, 1925) . 187 136 ELLIS L. YOCHELSON Subfamily Liospirinae Knight, 1956 190 Genus Liospira Ulrich and Scofield, 1897 190 Liospira species . 190 Subfamily Omospirinae Wenz, 1938 . 191 Genus Omospira Ulrich in Ulrich and Scofield, 1897. 191 Omospira ? holtedahli Y ochelson, new species 191 Family Eotomariidae Wenz, 1938 . 192 Subfamily Eotomariinae Wenz, 1938 . 192 Tribe Ptychomphalides Wenz, 1938 . 192 Genus Mourlonia de Koninck, 1883 192 Mourlonia mjoesa Yochelson, new species 192 Tribe Eotomariides Wenz, 1938 . 194 Genus Clathrospira Ulrich and Scofield, 1897 194 Clathrospira elliptica (Hisinger, 1829) 194 Clathrospira species . 197 Family Lophospiridae Wenz, 1938 . 197 Subfamily Lophospirinae Wenz, 1938 197 Genus Loxoplocus Fischer, 1885 . 197 Subgenus Lophospira Whitfield, 1886 197 Loxoplocus (Lophospira) species 197 Family Gosseletinidae Wenz, 1938 . 199 Subfamily Coelozoninae Knight, 1956 199 Tribe Coelozonides Knight, 1956 . 199 Genus Latitaenia Koken, 1925 . 199 Latitaenia rotelloidea (Koken, 1896) 199 Pleurotomariacean? new genus . 199 Superfamily Trochonematacea Zittel, 1895 201 Family Trochonematidae Zittle, 1895 201 Genus Trochonema Salter, 1859 . 201 Subgenus Eunema Salter, 1859 201 Trochonema (Eunema) species 201 Suborder Trochina Cox and Knight, 1960 . 201 Superfamily Platyceratacea Hall, 1859 201 Family Holopeidae Wenz, 1938 . 201 Subfamily Holopeinae Wenz, 1938 201 Genus Holopea Hall, 1847 . 201 Holopea henningsmoeni Yochelson, new species. 201 Genus Haplospira Koken, 1897 203 Haplospira new species. 203 Holopeid gastropod . 204 Family Platyceratidae Hall, 1859 204 Genus Cyclonena Hall, 1852 . 204 Subgenus Cyclonema Hall, 1852 204 Cyclonema (Cyclonema) species 204 Genus Naticonema Ferner, 1903 . 205 Naticonema ? praecursor (Koken, 1925) 205 MONOPLACOPHORA AND GASTROPODA 137 Order? Archaeogastropoda . 207 Su border Murchisoniina Cox and Knight, 1960. 207 Superfamily Murchisoniacea Koken, 1896. 207 Family Murchisoniidae Koken, 1896 207 Genera Indeterminate . 207 Suborder Undertain . 208 Superfamily Clisospiracea Miller, 1889 . 208 Family Clisospiridae Miller, 1889 . 208 Subfamily Clisospirinae Miller, 1889. 208 Genus Mimospira Koken, 1925 . 208 Mimospira cf. M. turrita, Koken, 1925 208 Order Caenogastropoda Cox, 1959 . 209 Superfamily Loxonematacea Koken, 1889 209 Family Loxonematidae Koken, 1889 . 209 Genus Loxonema Phillips, 1841 . 209 Loxonema septentrionale Koken, 1925 209 References . 210 Distribution of Middle Ordovician Monoplacophora and Gastropoda in the Oslo Region by horizon and district (chart). 212 Plates 1-8 and explanations of plates Introduction and acknowledgments This is the fifteenth in a series of reports designed to document the faunal, sedimentological and stratigraphical features of the Oslo Region. Middle Ordovician gastropods of this region were included by Koken (1925) in a monographic treatment of the Baltic Ordovician gastropods. Revision of Koken's work, in so far as it applies to the Norwegian specimens, is the principal objective of this paper. Many people have directly or indirectly aided this work. Ideal working facilities at the Paleontologisk Museum (Universitetet i Oslo) were provided by the Director, Professor Dr. Anatol Heintz. Norwe­ gian Ordovician specimens, property of the Riksmuseet, and large collections of comparative material from Sweden and Estonia were loaned by Fil. lic. Harry Mutvei, Palaeozoologiska avdelningen, Riksmuseet, Stockholm. Many types were included in these collections. Other important types were loaned by Dr. Fritz Brotzen, Sveriges Geologiska Undersokning, Stockholm, Sweden, Dr. Gerhard Regnell, Palaeontologisk-Geologiska Institutionen, Lunds Universitet, Lund, Sweden and Dr. H. Jaeger, Geologisch-Palaontologisches Institut und 138 ELLIS L. YOCHELSON -------------------- ------------ Museum der