Pseudobiceros periculosus Newman and Cannon, 1994
The diagnostic character for this species is the black background with a wide orange marginal band.
External anatomy: Relatively small body with black background of velvety appearance and a wide marginal bright orange band and an extremely narrow colorless transparent rim. The pseudotentacles are black without the marginal band, square and slightly ruffled with numerous eyes all over from the base to the tips. The ventral side is grey. The cerebral cluster has about 60 eyespost. A wide pharynx with simple folds with two male pores well separated on each side of the pharynx.
Internal anatomy: The male complex consists of two male gonopores, each one leading to an independent male system. Each system consist of a small rounded seminal vesicle connected to an extremely long and coiled ejaculatory duct, a big oval prostatic vesicle and a small stylet housed in a deep and ruffled antrum. There is single female system with a deep antrum and a short vagina, directed backwards, and surrounded by the cement glands.
This species has been found in Heron Islands and One Tree Island in the Great Barrier Reef, Australia. There is another report of this species for Hawaii.
This species has been found associated to colonial ascidians, under boulders at the reef crest.
The holotype is a whole mount of an entire specimen, and the paratype is an additional whole mount and a set of serial histological sections deposited at the Queensland Museum in Brisbane, Australia.
This species was included in the group 2, characterized by marginal bands, according to the categorization based on the color and color pattern made by Newman & Cannon (1994). Within this group most of the species are black with bright marginal bands but only Pseudoceros periaurantius has similar color and pattern with a single colored margin but it differs from P. periculosus in the gross morphology. P. flavomarginatus was described by Laidlaw (1902) as having similar color pattern but details regarding the reproductive anatomy and type of pharynx were not given so the species is considered Incertae Sedis.