Genus: Elongate, ovoid; anterior apex often curves over the peristome; non contractile (Carey, 1992). In front of cytostome a two-layered undulating membrane on right edge; contractile vacuole and cytopyge terminal; rose-colored; many species (Kudo, 1966).

B. americanum var. trinodatum 3 clips μm Vermont-Maine USA, 1999