Studies on the deep sea Protobranchia (Bivalvia); the family Tindariidae and the genus Pseudotindaria

In the present paper we have erected a new family of Protobranchia, the Tindariidae, to inckide those nuculanoid bivalves that lack a siphon but bear papillae on their posterior margin edge, ha\'e a single loop of tlie hind gut that penetrates the right side of the mantle, and possess a palp with few ridges. A new genus, Pseiidoiindaria, is created for those nuculanoid protobranch bivalves that have shell morphologies essentially similar to the Tindariidae but with soft parts that are markedly different. Siphons are present, the hind gut is a complex configuration of loops and coils on either side of the body and it does not penetrate the mantle, and palp ridges are numerous. The morphologies of the hard and soft part anatomies, the horizontal and vertical distributions, size-frequency histograms, and reproductive patterns of the tindariid and pseudotindariid species in our Atlantic samples are discussed. Two new species are described. On tlie basis of shell morphology, Tindaria and Pseudotindaria can be interpreted as recent descendants of the Paleozoic ctenodont Protobranchia.