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

Material — Three damaged, shelly specimens from the Discohelix orbis unit of the "originals collection". Measurements H Hl HPW D W AS AU lectotype - *6.8 4 18.9 *3.6 143° 150° GBa 2008/69/32/2/2 - *5.1 *4.5 *16.9 *3 - 149° Shape — Sinistral or false sinistral, discoidal, fairly not bilaterally symmetrical shell. In supposing dextral shell, angle of umbilical depression "-10° smaller than that of on spiral side. Form of spiral and umbilical cavities tend to spherical shape. Protoconch seems slightly raised in deeper excavated side of shell; strong re-crystallisation covers details. Earliest part seems to consist of globular nucleus and about one rounded whorl. Axial whorl section nearly trapezoidal in teleoconch with feebly concave, flattened or feebly convex spiral and umbilical sides; outer face evenly arched convex. Angulations, delimiting outer face, sharp and carinate from second whorl along whole teleoconch. Adult (apparent) aperture quadrangular, axially elongated. Entire peristome unknown. Sculpture — Protoconch seems smooth; spiral and umbilical sides of subsequent whorls covered by delicate growth lines and weak, collabral ridges. On earlier teleoconch whorls before penultimate whorl, ridges dense, equally strong and regularly repeating. Each ridge strengthens as distinct, collabrally elongate tubercle at crossing with carina, running along outer suture. Ridges become irregular on last whorl, just like tubercles. Concomitantly, gradually stronger, sparse and spine-like nodes develop on outer angulations of whorls. Low, wide undulation (ridge) of shell belongs to each node, both on spiral and umbilical sides. Outer face bearing fine and closely spaced spiral threads. Traces of spiral ornament on spiral and umbilical side observable only on last whorl as few (3-4) flat, obscure lines on some specimens. Remarks — STOLICZKA's (1861, Tafel III, 9-10) figures of Discohelix ornata (HÖRNES, 1853) are composed of morphological elements of two species. The more markedly ornamented specimens from the "Discohelix orbis

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'' inventory unit are regarded here as the name bearing ones of Discohelix ornata (HÖRNES, 1853). The remaining shells are representatives of a new species {Discohelix pseudornata, see below). The two species and Discohelix orbis are closely related to each other therefore some hardly distinguishable forms occur amongst the juvenile forms. All available Discohelix ornata specimens are strongly re-crystallized therefore the lack of ornament on the protoconch may be apparent. The adult size of D. ornata is much smaller than that of D. orbis (e. g. the diameter of shell is 16—20 mm in the earlier but exceeding 30 mm in the latter species). The adult stage is marked in D. ornata by the development of the strong nodosity

7 on the last whorl while the adult ornament does not differ substantially from the juvenile one in D. orbis. In the juvenile stage, D. ornata shows a rather regular repetition of the collabral riblets and granules on the keels but the same elements are only subregular in D. orbis. The tubercles may be lacking or cause only undulations of the continuous carinae in D. orbis but they are present every case and distinct in D. ornata; the carinae of the latter species seem actually to be composed of series of tubercles. Sometimes the tubercles are quite regular also in juvenile D. orbis but at the same time they have also dense spiral lineation; no lineation is observable on spiral and umbilical side of juvenile D. ornata. Present revision of the Discohelix species shows that the poorly preserved specimen, figured by SZABÓ (1979) as Discohelix cf. ornata (HÖRNES, 1853) from Sümeg (Bakony Mts, Hungary), is a fragment of a Discohelix orbis (because it has obscure traces of spiral threads also on spiral and umbilical sides). However, another fragment of this locality

7 represents Discohelix ornata in the gastropod fauna. The nodosed Discohelix from the Pliensbachian of Sicily, figured by M. GEMMELLARO (1911) who has interpreted D. orbis like STOLICZKA (1861), is also comparable but it belongs to a new species, needing description. Its nodes are more widely spaced and the specimens have significantly larger adult size than Discohelix ornata; other measurements are also considerably different. Discohelix ferox VON GÜMBEL, 1861 is also a nodosed species of comparable morphology and size, but the ratios of the shell and the details of the ornament are different. The whorls are more rapidly increasing therefore the number of whorls is much lower (6) than m D. ornata (10) by the same diameter. Another new, coarsely nodosed member of the "Discohelix orbis" group is Discohelix hallstattensis n. sp.; see for its distinction from D. ornata below. Distribution — Hallstatt, Hierlatz Alpe, Hierlatz Limestone, Upper Sinemurian (Oxynotum Zone); Bakony Mts: Sümeg, Upper (?) Sinemurian. Discohelix aff. ornata (HÖRNES, 1853) (Figure 15: M-O) pars 1861 : Discohelix réussi HÖRNES — STOLICZKA, p. 184, pi. 3, fig. 14 d. Material — Single whorl fragment (2008/69/35/2/1) from the collection of STOLICZKA's (1861) figured specimens, identified as "Discohelix réussi HÖRNES, 1853" [see Pentagonodiscus reussii (HÖRNES, 1853) below]. Measurements H HI HPW D W AS AU GBa 2008/69/35/2/1 +10/6.6 + = on pair of nodes/in interspace