Nomenclatural type of orders: corrections necessary according to Rules 15 and 21a of the Bacteriological Code (1990 Revision), and designation of appropriate nomenclatural types of classes and subclasses. Request for an opinion.

An important aspect of the Bacteriological Code (1990 Revision) is the designation of nomenclatural types to the various taxonomic ranks to provide a suitable reference point for the unambiguous identification of the taxon. Although the nomenclatural type of the species is the designated strain, and the nomenclatural type of the genus is the type species, the nomenclatural type of both the family and the order is the 'genus on whose name the name of the relevant taxon is based'. However, in some cases a genus has not been designated as the nomenclatural type of an order. Twelve cases that are contrary to the Rules listed and appropriate corrections are proposed. In addition, several classes have been named for which no nomenclatural type has been designated; this brings into question whether they can be considered to have been validly published, as well as highlighting the fact that they would be/are illegitimate.