In S. Pietro of Tuscania (11th cent.) it is adorned with strange dentilations; in simpler form it is found in S. Elia of Nepi, then in a great number of Romanesque churches (S. Zeno of Verona, S. Maria di Castello in Genoa, etc.), and in some of the early Gothic (S. Galgano). The double g. is characteristic of the Pisan and Apulian Romanesque architecture.
Bibl.: Mario Zocca