The gills close the loop. On a typical dorid the plume stands in a horseshoe, open at the back, with a gap where the two ends fail to meet. On this species they run right around into a complete circle, and that ring is the character that names it here.
Everything else about it is the genus doing what the genus does, which is hunting. These are predatory dorids that eat other sea slugs, and they are built for the chase: no mantle skirt overhanging the foot, the sides bare, the outline smooth, and a crawling speed that is noticeably higher than the animals they are after.
The size needs a note. The books give a maximum of six centimeters (2.4 in), but almost every animal you meet will be fifteen to twenty millimeters, so a small orange slug is not automatically a different species. Color runs from orange to yellow with darker pustules scattered over the back.
The name means unadorned, given by Bergh in 1880 to an animal that is bright orange and covered in spots, which tells you it was named from a specimen in preserving fluid. Alcohol strips the color out of these slugs within days, and a great many nineteenth-century names describe something nobody had seen alive.
- gills forming a complete closed circle rather than an open horseshoe
- orange to yellow body with darker pustules scattered over it
- usually a small animal, fifteen to twenty millimeters, though it can reach six centimeters
- no mantle skirt, sides of the foot exposed
