Notes on Oldhaminid Brachiopods

The aberrant brachiopod genera included in the family Oldhaminidae possess a peculiar brachial valve which has been thought to be an immobile internal plate. Detailed study of excellently preserved material suggests that the brachial valve was functional and served for protection and lophophore support. A ptycholophus lophophore was characteristic of the family and incurrent waters probably entered the shell via the distal ends of the lateral lobes while excurrent waters left it via the median incision. Two groups, one characterized by symmetrical and the other by asymmetrical musculature may be distinguished and do not coincide with the groups previously separated on the basis of symmetry or asymmetry of the brachial valve. Two new genera Rigbyella and Pseudoleptodus are described. A new species is questionably referred to Adriana. The Triassic genus Pterophloios is figured and discussed and is referred to the Oldhaminidae. Such ecologic data as exist are presented for each of the species considered.