Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 26. 2008. (Budapest, 2008)

tubercle but disappear before reaching carina of lower angulation. Growth-lines very fine, hardly visible on juvenile whorls then marked, dense "growth-riblets" develop that run from suture to suture (crossing also outer side on last whorl). "Growth-riblets" became truncated at parabolic ribs. Spiral ornament, consisting of fine, obscure lines (2—4), present only in interspaces of ribs at angulations of spiral side on two whorls following protoconch. Remarks — First time SZABÓ (1994) identified the Úrkút specimen as Asterohelix spinicosta (STOLICZKA, 1861). However, the change of the juvenile ornament into a different adult ornament on the last whorl, and the trochospiral coiling mode of the spire distinguish Asterohelix spinicosta from Asterohelix urkutensis n. sp., having a feebly concave spire, and the same type of ornament on the whole teleoconch. The size of the available Asterohelix urkutensis n. sp. specimen is bigger than that of an adult sísterohelix spinicosta therefore it can not be regarded as a juvenile shell of the latter species. Another similar species of the genus, the Pliensbachian Asterohelix mariae (M. GEMMELLARO, 1911), is separable by its last whorl, bearing neither carinae nor spines and by the inner whorls, where the spines are fewer than in Asterohelix urkutensis n. sp. Distribution — firkút (Bakony Mts), Lower(?) Sinemurian. Genus Pentagonodiscus WENDT, 1968 Type species: B/tompha/us reussii HÖRNES, 1853 Pentagonodiscus reussii (HÖRNES, 1853) (Figure 15) 1853: Euomphalus reussii HÖRN. — HÖRNES, p. 760. pars 1861 : Discohelix réussi HÖRN HS — ST< MJCZKA, p. 184, pi. 3, fig. 14 a-c. 1911: Discohelix réussi HÖRNES — M. Gl'MMKl.L \R< ), p. 215, pi. 9, fig. 14. 1968: Discohelix (Pentagonodiscus) reussii (HÖRNES, 1853) —

WEN DT, p. 574, pl. 110, figs. 22-24, text-figs. 2G, 3P, 5. 1979: Pentagonodiscus reussii (HÖRNES, 1853) — SZABÓ, p. 26, pl. 2, figs. 4-5; (text)fig. 6g. 1991: Pentagonodiscus reussii (HÖRNES, 1853) — CONTI & MONARI, p. 261, pi. 4, figs. 7-11, (text)fig. 12. 1994: Pentagonodiscus cf. reussii (HÖRNKS, 1853) — CONTI & MONARI, p. 201, pl. 1, fig. 8. Lectotype — GBa 2008/69/35/1 [selected by WENDT (1968)]. Material — Twenty specimens in the GBa and HGM collections Measurements II HI HPW D W AS AU GBa 2008/69/35/2 6.2 4.3 12.5 4.3 231° 111° Shape — Dextral, discoidal form, with less concave spire than umbilicus. While coiling of slightly trochospiral protoconch shows normal logarithmic spiral in "apical" view, outline of teleoconch whorls pentagonal. Spiral and umbilical side of whorls flat, but sometimes feebly concave or convex, outer side convex. Angulations sharp and persist along full length of teleoconch. Peristome internally thickened by suture-to-suture inner varix. Parietal lip slightly thickened by thin plate. Inner varices repeated periodically at intervals of somewhat less than 72°, their places marked on surface of whorls by collabral swellings both on spiral and umbilical sides and shallow successive depressions on outer side. Inner varix causes adaxial narrowing of internal space, while outer broadening shows axial expansion, thus area of whorl section remains unchanged. Rows of outer swellings, with <72° periodicity of its elements, resemble posteriorly arched spiral arms in apical or umbilical view. Sculpture — Nucleus and roughly half whorl smooth then 3—4 fine spiral lines appear both on spiral and umbilical sides. After about two whorls, these lines disappear. Adult sculpture onsets at about end of third whorl as reappearance of spiral ornament and beginning of first visible collabral elements. Pentagonal outline develops roughly simultaneously. Spiral sculpture consists of threads, separated by narrow incisions on whole whorl-surface. Collabral sculpture consisting of suture-tosuture costellae. These riblets become stronger toward keels, corrugate them and rapidly vanish outward. Spiral and transversal sculpture results in reticulate ornament. Remarks — Significant variability is observable in the development of the spiral ornament; it changes from distinct spiral threads (Figure 15: A—D) to obscure lineation, equally on spiral, umbilical and outer side of whorls (Figure 15: E—J). The shells are usually almost bilaterally symmetrical with a less concave spiral than umbilical side, but the spire may also be almost plane (Figure 15: K). From the earlier illustrations, those of STOLICZKA (1861 pi. 3, fig. 13., see photo in Figure 15: L) and CONTI & MONARI (1991, p. 261, pi. 4, Fig. 8) display also different specimens, having "tetragonal" outline because the deviations from the normal coiling are repeated four times in a coil, instead of five that is visible in the pentagonal specimens. In the other outer and inner shell characters, these specimens are rather near to Pentagonodiscus reussii, therefore they are regarded here as aberrant specimens. However, more abundant and better preserved material may result in different conclusion. Disregarding these cases, this characteristic species is easily distinguishable; however, there has been still no reliable method to