Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 75. (Budapest 1983)

Szabó, J.: Lower and Middle Jurassic Gastropods from the Bakony Mountains (Hungary). Part V.: Supplement to Archaeogastropoda; Caenogastropoda

row, a weak carina, then, 1 to 2 whorls after, a similar tuberculate row of weaker elements are visible. This latter one continues also up to the aperture. Below the periphery (i.e. the lower tubercle row), on the base, runs a weak carina. The growth lines are opisthocyrt on the whorls and orthocline on the base. Distribution — Bakony Mts.. Somhegy : condensed Subfurcatum and Garantiana Zones. Remarks — The last whorls are similar to those on the form described by HUDLESTON (1887—96) as Chyptaulax cf. undulation QUENST., but this latter has lower whorls, and the corresponding elements of its lower and upper tubercle row are connected by transverse ribs, and its suture is deeper. „Cerithium" undulation QUENSTEDT, 1858 itself is more similar to Cerithinellarigauxoidessp. n. in shape, but the sculpture is rather different: not only transverse ribs occur, but these are intersected by spiral cords, too. The closest form is Cerithinella cf. italica GEMMELLARO, 1878, which was figured by DUBAR (1948), especially that on pi. IV, fig. 12. On the other hand, its whorls are significantly lower and the ornament is more marked. The juvenile shell in itself can be identified with the genus Rigauxia (Zygopleuridae). This phenomenon possibly suggest descendence relationship. This type of shell-built is most common within the Nerineacea superfamily, but the arrangement of the here described species into this group can be ruled out, because none of the whorl-sections of the specimen sticked together from several fragments did show any internal spiral folds. Genus ?PROCERITHIUM COSSMANN, 1902 Subgenus ICosmocerithium COSSMANN, 1906 Procerithium (Cosmocerithium)? angulocostatum sp. n. (Plate II: fig. 7) H o 1 o t y p u s : Plate II : fig. 7. — Locus t y p i c u s : Bakonybél, Somhegy. — Stratum t y p i c u m : limestone infilling horizontal fissure. — Derivatio no minis: angulosus (Lat.) = angular; costatus (Lat.) = ribbed; referring to the characteristically ornamented whorls with broken ribs. Diagnosis : high, slightly cyrtoconoid spire; juvenile shell with suture to suture ribs, which is followed by whorls bearing broken, then divided ribbing; short riblets subsuturally on the last whorls ; fine spiral lines on every whorls. Measurements: H HL HA D W A Plate II: fig. 7. — — — 4.5 — 25-13° Material — Two fragmentary specimens. Shape — Dextral form with high cyrtoconoid shell, the whorls are rather low, their surface is strongly, then less concave on the juvenile and adult shell, respectively. The top of the concavity is situated at the lower third initially, and at the mid-whorl in later growth stages. The suture runs in a narrow groove, the periphery is angular, and the anomphalous base is similar to a cone of concave sides. Ornament — The surface of the whorls is covered by fine spiral lines, which are stronger on each sides of the suture than on the middle of the whorls. Immediately below the suture is situated the strongest one, from which rise the axial costellae. These run suture to suture and are straight on the juvenile whorls, later break at mid-whorl forming an adapical portion of slightly prosocline, and an other, of markedly opisthocline run. The two portions divide during growth, getting shorter, so that the lower ones become denser then about two whorls later fade out gradually. The upper ones are present within a narrow subsutural zone on the whole length of the available specimens. Because of the poor state of preservation, the sculpture of the base cannot be studied. Distribution — Bakony, Somhegy : ?Humphriesianum and condensed Subfurcatum and Garantiana Zones. Remarks — The uncertain generic arrangement can be assigned partly to the unknown peristome. The thick columella suggest the presence of a siphonal canal. Ifit will be proved, the question-mark shall be omitted, while in the case of its lack the possibility of zygopleurid relation should be considered. The uncertainty is increased by the fact that