Article 12. Names published before 1931
To be available, every new name published before 1931 must satisfy the provisions of Article 11 and must be accompanied by a description or a definition of the taxon that it denotes, or by an indication.
For the purposes of this Article the word "indication" denotes only the following:
12.2.1. a bibliographic reference to a previously published description or definition even if the description or definition is contained in a work published before 1758, or that is not consistently binominal, or that has been suppressed by the Commission (unless the Commission has ruled that the work is to be treated as not having been published [Art. 8.7]);
12.2.2. the inclusion of a name in an index to a work that is not consistently binominal, provided that the provisions of Article 11.4.3 are satisfied;
12.2.3. the proposal of a new replacement name (nomen novum) for an available name, whether or not required by any provision of the Code;
12.2.4. the formation of a family-group name from an available generic name [Art. 29];
12.2.5. in the case of a new genus-group name, the use of one or more available specific names in combination with it, or clearly included under it, or clearly referred to it by bibliographic reference, provided that the specific name or names can be unambiguously assigned to a nominal species-group taxon or taxa;
Example. A beetle genus-group name Isarthron was proposed by Dejean (1835) with eight associated species-group names. The latter were cited with an author (e.g. "luridum Fabr."); although no bibliographic references were given, by context the names can be assigned unambiguously to nominal species and Isarthron was therefore made available.
12.2.6. a combined description or definition of a new nominal genus and a single new nominal species, which then provides an indication for each name irrespective of whether the names are stated to be new;
12.2.7. the proposal of a new genus-group name or of a new species-group name in association with an illustration of the taxon being named, or with a bibliographic reference to such an illustration, even if the illustration is contained in a work published before 1758, or in one that is not consistently binominal, or in one that has been suppressed by the Commission (unless the Commission has ruled that the work is to be treated as not having been published [Art. 8.7]); and
The mention of any of the following does not in itself constitute a description, definition, or indication: a vernacular name, locality, geological horizon, host, label, or specimen.