http://www.seaslugforum.net/factsheet.cfm?base=crosviri
http://rfbolland.com/okislugs/crosviri.html
http://www.sea-slug.com/species/umiusi144.htm
http://online.divers.ne.jp/ono/seaslug6/room6-5.html
http://www.ne.jp/asahi/kappa-kuri/miyamoto/OSEHOO/umiushi235.html