Revision of the Recent species of the genus Nemocardium Meek, 1876 (Bivalvia, Cardiidae), with the descriptions of three new species

The genus Nemocardium Meek, 1876, is traditionally considered a relic of the past. Morphometric and morphological analyses reveal that the well-known species N. bechei (Reeve, 1847) is in need of taxonomic reconsideration. In this paper, five species are recognized, three of which are new to science: N. bechei from Taiwan, Philippines and Indonesia; N. probatum (Iredale, 1927) from northern Australia; N. australojaponicum spec. nov. from southern Japan and Korea; N. enigmaticum spec. nov. from the South West Pacific and N. fulvum spec. nov. from Mozambique, Madagascar, Seychelles, India, Philippines and Vanuatu. All but the last species seem to occur perfectly parapatrically. With N. fulvum spec. nov., which is not confined to the Central Indo-Pacific but covers large parts of the Indian Ocean as well, the longitudinal range of Nemocardium is much wider than hitherto thought. A substitute lectotype is designated for Cardium bechei Reeve, 1847, and the New Zealand genus Varicardium Marwick, 1944, is synonymized with Nemocardium.