Myrtoessahyas, a new valvatiform genus and a new species of the Hydrobiidae (Caenogastropoda, Truncatelloidea) from Greece Author Radea, Canella Author Parmakelis, Aristeidis Author Giokas, Sinos text ZooKeys 2016 640 1 18 http://dx.doi.org/10.3897/zookeys.640.10674 journal article http://dx.doi.org/10.3897/zookeys.640.10674 1313-2970-640-1 B4EA1C647EBB4B89B46A360A9CCB11DB B4EA1C647EBB4B89B46A360A9CCB11DB Myrtoessa Radea gen. n. Type species. Myrtoessa hyas sp. n. by original designation. Diagnosis. Shell minute (maximum height 1.05 mm, maximum width 1.30 mm), valvatiform with more or less depressed spire; operculum without peg; central tooth with one basal cusp on each side; ctenidium and osphradium present; penis long, flat, blunt, with wide wrinkled proximal part and narrow distal part with a sub-terminal eversible papilla; female genitalia with large pyriform bursa copulatrix, renal oviduct non-pigmented, coiled in an ε (Greek)- shape; two seminal receptacles lying parallel on the renal oviduct and rather close to each other, a small distal receptacle (Sr1) and a larger proximal one (Sr2). Etymology. The generic name derives from the Greek mythology: Myrtoessa (Μυρτώεσσα in Greek) was a naiad nymph in Arkadia. Gender feminine.