Two new species of the family Hydrobiidae (Mollusca : Caenogastropoda) from Austria

Two new species of the family Hydrobiidae from Austria are described. One b elongs to the genus Belgrandiella A. J. Wagner, 1928, the second is allocat ed to Bythiospeum Bourguignat, 1882. The crenobiontic Belgrandiella species is characterized by one autapomorphic character state of the genital syste m and by a unique combination of states which are shared with other species . The second species, a stygobiont, is tentatively attributed to Bythiospeu m, because its description is based only on shell characters. Both species are known from very restricted ranges corresponding to the distributional p attern of their congeners. In addition, data of 13 abiotic parameters measured over a period of more t han 5 years in the springs where the new species were found are presented. The Values of these parameters are characteristic for natural, carbonate br ooks. Contamination with fecal bacteria suggests influence through agricult ure or may be caused by feces of mammals. Chemically, agriculture and fores try appear to have no significant impact on the springs investigated.