Revision of the genus Parabornia (Bivalvia : Galeommatoidea : Galeommatidae) from the western Atlantic, with description of a new species from Brazil

Parabornia palliopapillata n, sp. (Galeommatidae) is described from small b ivalves found attached to the abdomen of the stomatopod crustacean Lysiosqu illa scabricauda (Lamarck) (Lysiosquillidae from the Rio de Janeiro and Sao Paulo coasts, Brazil. The shell is thin, flat, white, and smooth. The hing e possesses a pair of small symmetrical cardinal teeth in each valve. The m antle border has 4 marginal folds, the third being entirely papillated, wit h only the umbonal region lacking papillae. The foot has a small byssus, a ventral furrow and an anterior flower-like organ. The style sac of the stom ach is separated from the intestine. The incubation of ova occurs in both d emibrancks. A complementary redescription of P. squillina Boss, 1965, the s ingle species of the genus up to this time and associated with the same hos t, is provided, based on paratypes from Panama. The two species differ main ly in details of the mantle border, gill, digestive tract, anterior muscula ture and shape of the flower-like organ. A discussion of the family assignm ent of the genus is also provided.