407 ACTA ZOOLOGICA BULGARICA Acta zool. bulg., 64 (4), 2012: ???-??? Introduction The very irst data on freshwater mollusks of Upper Thracian Lowland was given by HristovitcH (1892) reporting Lymnaea stagnalis Lamarck 1799 from two localities: near the village of Zlokuchene and Kovachevski Giol, both near Maritsa River. After this publication the list of mollusk species recorded in the region grew by further works of the malacologists vavra (1893), YourinitscH (1906), Hesse (1911), Haas (1911), WoHLberedt (1911), Wagner (1927), büttner (1928), Petrbok (1941), drenski (1947), urbanski (1960), and some hyd- robiologists as uzunov, kovacHev (1985), uzunov et al. (1998), russev et al. (1981, 1984) and others who provided information on zoobenthic communi- ties and condition of their habitats. The most interesting report from all these pa- pers was the one of Lymnaea (Gulnaria) auricularia var. ampla Hartm. (= Radix ampla Hartmann, 1821) by Hesse (1911), which record was omitted in the further literature published for Bulgaria. In his work on Bulgarian freshwater malaco- fauna angeLov (2000) summarized all the informa- tion available for the country. The author reported 9 exact localities in Upper Thracian Lowland: Floods at Maritsa River near Plovdiv (the richest in species recorded – 21): Valvata piscinalis (O. F. müLLer 1774), Valvata cristata (O. F. müLLer 1774), Radix auricularia (Linnaeus 1758), Stagnicola palustris (O. F. müLLer 1774), Stagnicola corvus (gmeLin 1791), Lymnaea stagnalis Lamarck 1799, Planorbis planorbis (Linnaeus 1758), Planorbis carinatus O. F. müLLer 1774, Anisus vortex (Linnaeus 1758), Anisus leucostomus (miLLet 1813), Bathyomphalus contortus (Linnaeus 1758), Gyraulus albus (O. F. müLLer 1774), Gyraulus piscinarum bourguignat 1852, Gyraulus crista (Linnaeus 1758), Hippeutis complanatus (Linnaeus 1758), Segmentina nitida (O. F. müLLer 1774), Planorbarius corneus (Linnaeus 1758), Physa fontinalis (Linnaeus 1758), Aplexa hypnorum (Linnaeus 1758), Sphaerium corneum (Linnaeus 1758), Pisidium amnicum (O. F. müLLer 1774), Rice ields at Pazardzik: Planorbarius cor- neus (Linnaeus 1758); Rice ields at Plovdiv (c): Planorbarius corneus (Linnaeus 1758); Rice ields Freshwater malacofauna of Upper Thracian Lowland (Southern Bulgaria) Dilian G. Georgiev Department of Ecology and Environmental Conservation, University of Plovdiv, 24 Tzar Assen Str., BG-4000 Plovdiv, Bulgaria; E-mail: diliangeorgiev@abv.bg Abstract. The study was carried out during a ive-year period, from 18. 01. 2004 to 10. 10. 2011 from 53 localities at Upper Thracian Lowland. It summarized a total of 51 species of freshwater mollusks (39 species of snails and 12 species of mussels) reported for Upper Tracian Lowland from which 5 we consider not to occur in this area, 2 species names used before were misidentiied and refer to other species, 5 were species report- ed before, but their occurrence in the area is under question, and 5 were new records for this geographic region. The most widely distributed species were Physella acuta, Radix auricularia, Planorbis planorbis, and Unio pictorum, the rest ones seemed to be rare or with low population densities in the area. Key words: Gastropoda, Bivalvia, plain, distribution, habitats.