Not quite correct Philippe! Although it sounds logical at the first glance, "page priority" is a myth. However, the principle of priority says that (usually) the oldest available name is the valid one. Of two names published in the same work nobody can say which one is older since this is determined solely from the date of publication. Names published in the same work (unless issued in parts) have logically the same date of publication.
See also here:
http://iczn.org/content/there-such-thin ... y%E2%80%9D
There have been attempts to introduce a rule for page or line priority in the 1940s or 50s, but it has been abandoned in favor of the first reviser principle already before the publication of the first 'modern' Code (1961).
Rico Morgenstern wrote: Poll (1986) has fixed, as the First Reviser (Art. 24.1).....
Sorry, a typing error, actually it should read "Art. 24.2".
http://www.nhm.ac.uk/hosted-sites/iczn/ ... 4&nfv=true
Poll (1986) was the first to synonymize the simultaneously published generic names Neolamprologus and Paleolamprologus (and Variabilichromis) and selected Neolamprologus as the valid name. The latter has priority on account of this alone, for whatever reason Poll has chosen that name.