The shell is minute, fragile, transparent, elongate elliptical, equivalve, slightly inequilateral. The valves are rather convex, closed along all sides. Umbones are broad, not prominent; beaks just behind midline. All margins are evenly curved, the posterior margin more strongly than the anterior margin. Lunule, escutcheon and nymph are absent. The hinge plate is long, narrow, weak, with a interval under the umbo; anterior part of hinge plate is almost twice as long as posterior part; no cardinal teeth; 3-4 anterior and 3-4 posterior lateral teeth, which are weak, irregular, oblique, lamelliform. Some growth lines and usually some concentric threads are visible near the ventral margin. Muscular scars, as well as pallial line, are not clear.
Up to 0.6 x 0.8 mm.
North Sea coast of the Netherlands, Belgium and France (Distr. P. guilonardi).