The gasflame nudibranch is a large nudibranch densely covered with cerata. It is usually between 50 and 80 mm in length, but may reach 120 mm. It has highly variable coloration and may be pale-bodied with orange ceratal tips, yellow-bodied with blue ceratal tips, salmon-coloured with brown tips or even black with blue ceratal tips. Its rhinophores are perfoliate and vary in coloration with rest of animal, separated by a rhinophoral crest of unknown function.