(1996). Systematics and evolution of Littorina. The Ray Society 463p. Rolán-Alvarez, E. (2007). "Sympatric speciation as a by-product of ecological adaptation in the Galicia Littorina saxatilis hybrid zone". Journal of Molluscan Studies 73: 1–10. Rolán-Alvarez, E.; Johannesson, K. & Erlandsson, J. (1997). "The maintenance of a cline in the marine snail Littorina saxatilis: the role of home site advantage and hybrid fitness in ecotype formation". Evolution 51: 1838–1847. External links In the British Isles As an invasive species in San Francisco Bay Littorinidae Gastropods described in 1792 Taxa named by Giuseppe Olivi