Three haloxenous species out of the 14 known members of the genus have been reported so far from inland saltwaters, whereas never from true marine environments. This genus is quite easy to identify: they are dorso-ventrally compressed, with a well developed foot; they move by gliding on the surface, repeatedly protruding and retracting the foot, while the cilia of the head convey food particles to a rake close to the mouth opening.
Body length: 200-700 μm. Trophi are very small and each uncus has 2 major teeth.
Body elongate, usually broadest in trunk. Head oval, rounded in front, flattened, wider than neck. Rostrum not retractile, short, with variably shaped lamellae and cilia. Trunk often flattened dorso-ventrally. Foot small, narrow. Two spurs and three toes. Corona a homogenous ciliated field on ventral side of head; a paired series of teeth at base of ciliated area surrounding mouth opening (the rake) for food collection. Corona not retracted when moving; movement by gliding. Unci with 2/2 major teeth. Oviparous (except A. grandis Murray, 1910).
The species of this genus are found in Europe, Northern America and Southernmost Southern Hemisphere.