» Riellaceae    Description of the characteristics of this family, the genus Riella and the species R. americana and affini. Riella is unique among hepatics in living submerged in fresh or brackish water in arid and semiarid regions.    http://www.mobot.org/plantscience/bfna/V3/RielRiellaceae.htm

» Sphaerocarpaceae    Description of the characteristics of this family, the genus Sphaerocarpus and the species S. cristatus, donnellii, drewii, hians, sphaerocarpus and texanus.    http://www.mobot.org/plantscience/bfna/V3/SphaSphaerocarpaceae.htm