Habitat: it lives in the circalittoral zone, on bottoms of different nature: muddy, sandy, detrital ones but also in the coralligenous- It is collected in remarkable depth too. Distribution: it can be found all over the Mediterranean, but never common.
Notes: shell quite solid, equivalve, inequilateral, circular in outline, valves convex, umbo placed in the centre and bent anteriorly. In the anterior dorsal part there is one slight sinus clearer in premature specimens. Sculpture made by numerous concentric circles covering valves surface wholly. Two cardinal teeth per any valve, the anterior one of which, of the left valve, and the posterior one, of the right valve, are bifid. Furthermore there can be present single lateral teeth more or less obsolete. Juvenile forms are more stretched anteriorly in outline, they have one dorsal sinus more well defined and an umbo more protuberant.
Uniform dirty white in colour, periostracum very thin and caducous, light brown in colour. Inside of valves white, ventral margin smooth. Varieties depressa and gibba Jeffreys', 1864, are included in the morphological variability field of this species. The two species recently setup: L. spelaeum Palazzi & Villari, 2001 and L. kazani Salas & Woodside, 2002 are very similar to borealis: the first one is recognizable due to a closer sculture, to an outline less roundish and to smaller sizes, while kazani is distinguishable due to the hinge characteristics mainly, besides a different habitat and geographical distribution. The adult specimens average measures are about 35 mm in diametre.