http://scilib.ucsd.edu/sio/nsf/fguide/mollusca1.html
http://www.seaslugforum.net/showall/tritbell
http://www.guiamarina.com/gallery/v/Antarctica/01+animals/04+Mollusca/Opisthobranchia/Tritoniella+belli/
http://www.medslugs.de/E/Atl-SW/Tritoniella_belli/Selection.htm