First record of the family Korethrasteridae (Asteroidea: Velatida) from Japan and descriptions of two new species

Two new species, Remaster boninensis n. sp. and Peribolaster niveus n. sp., from Japanese waters have been described. These species have been included in the family Korethrasteridae, based on the presence of a plump and petaloid body shape, absence of a supradorsal membrane, interradial grooves floored by chevron plates, and transversely extending adambulacral plates. These were the first species of Korethrasteridae found in Japanese waters. Remaster boninensis n. sp. was assigned to the genus Remaster in having distally flaring abactinal spines that are united by the skin into hollow funnel-shaped paxillae, but it differs from the congeners in the number of arms, absence of noticeable primary radial plates, and length of interradial grooves. Peribolaster niveus n. sp. was assigned to the genus Peribolaster in having acicular abactinal spines that are united by the skin into hollow funnel-shaped paxillae, but it differs from the congeners in the presence of noticeably flaring actinolateral spines, one suboral spine on each oral plate, and biserial tube feet.