Systematics of Melanopsis from the coastal plain of Israel (Gastropoda: Cerithioidea)

Based on conchiometrics of 161 snails of the freshwater genus Melanopsis collected from six sites in the Coastal Plain of Israel, three species were identified: buccinoidea (Olivier), costata (Olivier) and saulcyi Bourguignat. Species previously described from this region (lampra Bourguignat, phoeneciaca Bourguignat, belusi Bourguignat and hebraica Bourguignat) are placed as synonyms. Within buccinoidea, the slim, elongate shells of the northern Coastal Plain differ from Jordan Valley ones in their fewer ribs, shallower notch and more conic shape. While most samples of the Coastal Plain fall into clearly distinct species, in Sa'adia ribbed shells gradually merge into smooth ones. The frequency of intermediates is high, but the mechanism maintaining these possible hybrids is unknown.