The Architectonicidae and Mathildidae (Gastropoda, Heterobranchia) of the Miocene Paratethys Sea-victims of the Miocene Climatic Transition Author Harzhauser, Mathias 0000-0002-4471-6655 Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria. mathias. harzhauser @ nhm-wien. ac. at; https: // orcid. org / 0000 - 0002 - 4471 - 6655; mathias.harzhauser@nhm-wien.ac.at Author Landau, Bernard 0000-0002-4471-6655 Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria. mathias. harzhauser @ nhm-wien. ac. at; https: // orcid. org / 0000 - 0002 - 4471 - 6655; & Naturalis Biodiversity Center, P. O. Box 9517, 2300 RA Leiden, Netherlands; Instituto Dom Luiz da Universidade de Lisboa, Campo Grande, 1749 - 016 Lisboa, Portugal; and International Health Centres, Av. Infante de Henrique 7, Areias São João, P- 8200 Albufeira, Portugal. bernardmlandau @ gmail. com; https: // orcid. org / 0000 - 0002 - 7768 - 8494 & Natural History Museum Vienna, Burgring 7, 1010 Vienna, Austria. mathias. harzhauser @ nhm-wien. ac. at; https: // orcid. org / 0000 - 0002 - 4471 - 6655; mathias.harzhauser@nhm-wien.ac.at text Zootaxa 2023 2023-11-14 5370 1 1 74 https://www.mapress.com/zt/article/download/zootaxa.5370.1.1/52270 journal article 10.11646/zootaxa.5370.1.1 1175-5334 10147814 48903495-7C6C-46E4-9B1B-D6A2F2781873 Genus Heliacus d’Orbigny, 1842 Type species. Solarium herberti Deshayes, 1830 [= Heliacus cylindricus ( Gmelin, 1791 ) ]; by monotypy. Present-day, Atlantic. Original diagnosis. “ Testa orbiculato-conica, trochiformi, transversim costata, longitudinaliter striata , nigrofusca; spira elevata, anfractibus quinis subconvexis; umbilico angusto, crenato, intus tricostate; apertura subrotunda” [Shell orbicular-conical, trochiform, transversely ribbed, longitudinally striated, black-brown; a raised spiral, subconvex with bends; umbilicus narrow, crenate, tricostate inside; aperture sub-rounded] (d’Orbigny 1842: 68). Revised description. “ Teleoconch: small to medium-sized (usually 6-13 mm , rarely over 20 mm }, depressed to tall roundly cone-shaped, with narrow to very wide umbilicus (ca. 8-40% of shell diameter); whorls weakly to distinctly bulging; sculpture: spiral ribs with relatively large nodules on entire surface; number of ribs constant, only between lower peripheral and infraperipheral ribs occasionally with 1 ± strong additional rib; apical side: subsutural rib, single midrib (or two narrow ones) and upper peripheral rib usually equally developed, rarely upper peripheral rib somewhat stronger; periphery formed by lower peripheral rib and only slightly weaker infraperipheral rib (occasionally with additional rib between them); upper point of whorl attachment at or below lower peripheral rib; base usually with 5 spiral ribs, increasing in width towards umbilicus; umbilical wall usually with 1-2 strong, narrow spiral ribs ” ( Bieler 1993: 184 ) ( Fig. 2 ). Synonyms. Torinia J. E. Gray, 1842 , type species Trochus cylindraceus Dillwyn, 1817 [= Heliacus cylindricus ( Gmelin, 1791 ) ]. Present-day, Atlantic.