Phreatic Hydrobiids (Gastropoda: Prosobranchia) from the Edwards (Balcones Fault Zone) Aquifer Region, South-central Texas

This paper provides a systematic analysis of phreatic hydrobiids from 23 localities in southcentral Texas, including 14 artesian wells and four springs in the Edwards (Balcones Fault Zone) Aquifer. Hauffenia micra (Pilsbry & Ferriss) and Horatia nugax (Pilsbry & Ferries) are redescribed as members of a new genus, and two additional new genera, seven new species and one new subspecies are also described (Table 2). Detailed morphological descriptions, provided for all taxa, emphasize characters of the shell, operculum, pallial cavity, digestive system, and reproductive system of both sexes. Two of the new genera are monotypic littoridinines having affinities with phreatic or epigean littoridinines from Mexico. The affinities of the third new genus, a hydrobiine which includes seven well-differentiated species, remain unclear. While all of the species are found in the Edwards (Balcones Fault Zone) Aquifer, at least four of the species are probably found in other aquifers of south-central Texas as well. With the description of seven new hydrobiid species, the rich and still poorly sampled troglobitic biota of the Edwards (Balcones Fault Zone) Aquifer now totals 39 troglobitic animal species, including four vertebrates