this website exists no more:
http://www.biology.ucsc.edu/classes/bio161l/NUDI/tbimacul.html
http://www.seaslugforum.net/showall/thorbima
http://slugsite.us/bow/nudwk528.htm
http://www.underwaterkwaj.com/nudi/california/c019.htm
http://www.medslugs.de/E/Pac-NE/Thordisa_bimaculata/Selection.htm
http://smg.photobucket.com/albums/v109/divinman/Nudibranch%20archive/?start=120
http://scottpenny.smugmug.com/gallery/3881249_R9eMK/6
http://www.nudipixel.net/species/thordisa_bimaculata/