Discodorididae includes flattened dorids with tubercles, papillae or
caryophyllidia on the notum. Most are cryptic and nocturnal. It was
recently revised to
include the families Archidorididae, Asteronotidae, Kentrodorididae,
Platydorididae, and Rostangidae. It is the largest nudibranch family in
Hawaii with about 58 known species in 14 genera (Asteronotus, Atagema, Carminodoris, Diaulula, Discodoris, Geitodoris, Halgerda, Jorunna, Paradoris, Peltodoris, Platydoris, Rostanga, Sclerodoris, and Thordisa).
It's possible that the species listed as "Platydoris sp." in Kay & Young
(1969) might be Platydoris sanguinea
Bergh, 1905 but it needs confirmation. The animal referred to as
species with broad thin margins..." on page 182 of Edmondson, 1946 is
probably in this family but is likely unassignable. Dai Mar Tamarack
sent a photo of an animal that may turn out to be an additional species
of Rostanga. However, it requires confirmation.