Szabó János szerk.: Fragmenta Mineralogica Et Palaentologica 26. 2008. (Budapest, 2008)
Genus Plectotrochus n. gen. Type species: Trochuspkctits STOLICZKA, 1861 Diagnosis — Trochiform shell, consisting of numerous, extremely low whorls, separated by feebly impressed suture. Juvenile shell part prominently acute, but subsequent whorls have cyrtoconoidal outline. Base flat, aperture narrow, fissure-like. Disregarding edge of thin parietal callus, peristome unknown; whorl cross-section indicate extremely short columellar lip and a practically triangular peristome. Shell markedly sculptured; nodosed subsutural carina and regularly repeating, dense, collabral costellae compose ornament of whorls; base densely lineated (see details in description of type species below). Remarks — The general shell shape well fits to a genus group of the Proconulinae (like Epulotrochus, Anticonulus, Dimorphotectus, Muricotrochus) , however Plectotrochus plectus (STOLICZKA, 1861) has a unique style of the ornament, therefore can not be accomodated in the other genera. Ribbed ornament of different type found in a few Proconulus species, but their shape is different because their whorls are higher. Plectotrochus plectus (STOLICZKA, 1861) (Figure 63) 1861: Trochus plectus STOL. — STOLICZKA, p. 171, pl. 1, 19. Lectotype — (monotype) GBa 2008/69/16/1. Material — Single specimen without earliest juvenile whorls, and major part of the peristome is also missing. Measurements H lectotype *8 HL *3.5 HP *1.8 D 6.2 W *3.2 AA AL *37(-50)° 30° Shape — Small, trochiform shell of low whorls separated by shallow impressed suture. Preserved part of juvenile shell acute conical but turning into distinctly cyrtoconical outline with growth. Number of preserved whorls 12; reconstructed shell consists of >15 whorls. Periphery sharply angulate; base flat; no sure trace of umbilicus found. On parietal region thin inducture preserved, columellar lip must be short (dislike original figure) but broken. Sculpture — Tubercled subsutural spiral thread present already on earliest preserved whorl, that rapidly (in two whorls) strengthen as carina w T hile tubercles becoming nodulae. From tubercles weak ridges run collabrally to lower suture, that becoming club—like ribs with growth. Their thicker (abapical) ends form another, weaker row of nodulae on last two whorls and causing impression of appearance of another (suprasutural, peripheral) carina. Thin incision follows subsutural carina on its abapical side, cutting ribs. Weak spiral thread folloAv this lines for abapically and causing irregular appearance of third (middle) row of tubercles. Base densely covered by extremely fine lines but most of them eroded. Remarks — The final growth stage of a true "trochiform shell" (i.e. the conical or coeloconoidal last whorls) lacking. Therefore the only available shell may be a not completely adult one. Distribution — Hallstatt, Hierlatz Alpe, Upper Sinemurian (Oxynotum Zone). Figure 63 — Plectotrochus plectus (STOLICZKA, 1861), holotype. — 19 a-b: copy of original figures from Soi.lCZKA (1861) Tafel I; A-C: the holotype in "apertural" (A), dorsal (B) and basal (C) views, xl; D: magnified "apertural" view to show the peculiar ornament; x5. Genus Dimorphotectus COSSMANN, 1918 Type species: Pectushoernesi KOKEN, 1896 Dimorphotectus simonyi (HÖRNES, 1853) (Figure 64) 1853: Trochus Simonyi — HÖRNES, p. 759. 1861: Trochus Simonyi HÖRN. — STOLICZKA, p. 170, pl. 1, fig. 17. Lectotype — GBA 2008/69/14/1 (selected here). Material — Two specimens in the "originals collection" and 68 specimens in the "background" material.
