Subclass Opisthobranchia (including order aplysiomorpha (mainly sea hares)); sacoglossa; pleurobranchomorpha; and nudibranchia (colourful sea slugs with gills exposed on the dorsal surface.)

More nudibranch images can be seen in the Fish Quay, St. Peter Port harbour gallery at http://sealord.smugmug.com/gallery/3514928#200787061