Abstract
Peptococcaceae is proposed as a new family in the order Eubacteriales to include three genera of presently known gram-positive, anaerobic, coccal organisms: Peptococcus Kluyver and van Niel, Peptostreptococcus Kluyver and van Niel, and Ruminococcus Sijpestein. The type genus of this family is Peptococcus. Descriptions of these taxa are given, and where necessary the original descriptions have been expanded and brought up to date.