Koreamya arcuata (A. Adams, 1856) gen. nov.(Galeommatoidea: Montacutidae), a commensal bivalve associated with the inarticulate brachiopod Lingula anatina

We describe the shell, soft anatomy, and reproduction of the montacutid bivalve, Koreamya arcuata (A. Adams, 1856) gen. nov. Contrary to most montacutids the outer demibranch has been preserved, although in a reduced state. The species is a protandrous consecutive hermaphrodite which stores sperm in a groove-shaped ctenidial seminal receptacle. The particular type of sperm receptacle and the presence of a lithodesma in Koreamya indicate an affinity to Montacutona Yamamoto & Habe, 1959, but the shells of the two differ widely in shape and proportions. The species is a commensal, and lives permanently attached to the valves near the shell gape of Lingula anatina at several Korean intertidal flats. It is also known from the Philippines, SE India and W Australia.