« Shell inflated, ovate to rhomboidal or trigonal, subequivalve. Posterior rostrum absent. Outer surface with adherent periostracum, smooth or granulate to spiculate. Ligament external, opisthodetic, without a lithodesma. Dorsal margins of valves united by fused periostracum. Hinge edentate, or with a variable cardinal tooth in right valve. Interior of valves nacreous. » – Poutiers & Bernard: “Carnivorous bivalve molluscs (Anomalodesmata) from the tropical western Pacific Ocean”, Mémoires du Muséum national d’histoire naturelle vol.167, Paris 1995, p.153.
 

Shell surface granulate. Left valve edentate, cardinal tubercle of the right valve reduced or absent. Ligament not deeply sunken.
 

« Shell transverse, subequivalve, entirely closed, punctate or granulated; in both valves the hinge bears a subspatulate cardinal tooth and two oblique teeth anteriorly. » – E. Forbes: “Report on the Mollusca and Radiata of the Aegean sea”, Reports of the British Association for the Advancement of Science for 1843, London 1844, p.191. The prefix comes from the ancient greek πόρος, which refers to some kind of aperture or channel and may express the fact that this genus was considered by Forbes as a passageway to Mya Linnaeus.