Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 72. (Budapest 1980)

Szabó, J.: Lower and Middle Jurassic Gastropods from the Bakony Mountains (Hungary). Part II.: Pleurotomariacea and Fissurellacea (Archaeogastropoda)

Genus PYRGOTROCHUS P. FISCHER, 1885 Pyrgotrochus periferialis sp. n. (Plate III: fig. 6) 71874: Pleurotomaria cf. princeps KOCH et DUNKER — G. G. GEMMELLARO, p. 95, pl.

12, fig. 17. Holotypus : Plate III: fig. 6. — Locus typicus: Lókút, Kericser. — Stratum typicum: Hierlatz limestone. — Derivatio nominis: Referring to the fact that it is an atypical Pyrgotrochus species. — Diagnosis : High, conical shell with slightly convex, but not angular selenizone; whorl-surface without angulation and with covering of spiral lines. Measurements: H HL HA W D A Plate III: fig. 6 28 18.5 10 11 24 43° Material — The majority of the available 17 specimens preserves the shell, but all are more or less fragmentary. Shape — Dextral form with conical spire. The surface of the whorls is somewhat convex, the whorl-section is tetragonal. The broad, slightly convex selenizone courses somewhat below the middle of the whorls. The base is slightly convex, with moderately open umbilicus. Peristome cannot be studied in the available material. Ornament — The surface of the whorls, as well as the base, is ornamented with spiral lines. The transverse ornamental elements are the growth-lines and the transverse riblets along the suture and the periphery. Sometimes these riblets are replaced by elongated nodes. The corresponding elements of these nodes are distinct, sharp costellae also on the juvenile whorls. Remarks — In contrast to P. periferialis, a generally characteristic feature in the species of Pyrgotrochus is the flattened, or slightly concave whorl-surface. Similar is the case in P. princeps (ROCH et DUNKER, 1837). The convex whorl-surface results in a similarity to the shape of genus Pleurotomaria. However, the lack of the angulation on the whorl-surface, as well as the clearly visible longitudinal swollen band of the periphery, marks the generic state of this species distinctly. P. periferialis resembles most closely Pleurotomaria cf. princeps of GEMMELARO (1874) from the previously figured forms. However, this latter is distinguished in having a 10 to 15° greater spire angle resulting in different dimensions. The other forms, which were described and figured as P. princeps, show distinct tuberculation above and below the suture (as well as on the periphery), rarely convex band between the two rows of tubercles, and crytoconoid shape, at least in the juvenile stages. Additionally, the whorls are lower (i.e. the H/HA and the H/HU ratios are bigger). This latter feature appears also in the similarly shaped, but non-tuberculate "Pleurotomaria decipiens var. turrita''' of DESLONGCHAMPS, 1849 (="P. Mariae" D'ORBIGNY, 1853). Distributione

— Western Sicily?: Middle Liassic; Bakony Mts., Kericser: beds with mixed Obtusum to Ibex Zone fauna and Davoei Zone; Hamuháza: Davoei Zone. Pyrgotrochus solus sp. n. (Plate III: fig. 7) Holotypus : PÍ. Ill: fig. 7 — Locus typicus: Bakonybél, Somhegy. — Stratum typicum: Limestone infilling of a horizontal submarine fissure: — Derivatio nominis: solus (Lat.) — single. — Diagnosis : Extremely high spire with concave outline, the peripherally swollen band occurs only on the juvenile shell, the selenizone is concave, the ornamentation consists of spiral and transverse threads. Measurements: H HL HA W D A Plate III: fig. 7 50 15 8.5 14 30 30-36° Material — A single specimen. Shape — Dextral form with high shell of concave outline. The shell consists of very numerous whorls with flattened surface, on lower margin of which a conspicuous spiral convexity courses. This convexity tends to fade out, and becomes almost entirely flattened on the last whorl. The selenizone is situated directly above this convexity. This is wide, flat initially, becoming concave from the last sixth or seventh whorl onwards. The periphery is rounded-angular, and the base is convex, with narrow, open umbilicus. The umbilical margin is angular. The peristome is unknown, but the whorlsection suggests a possibly axially flattened, tetragonal shape. The inner space of the whorls is narrowed at the portion bordering the umbilicus, by a distinct, longitudinal ridge, the end of which is probably well visible on the peristome.