ARENARIO. – Shortly after the discovery of the Christian cemetery galleries on the Via Salaria in the spring of 1578, the Sanctorum Martyrum Abundii presbyteri, Abundantii diaconi, Marciani Ioannis et filii eius Passio (Rome 1578) was published, together with a list of texts that designated the catacombs as arenaria. With the exception of Bosio, all the early writers on underground Rome held that the catacombs were former sand quarries used by the Christians. One of the testimonies most frequently adduced was a passage from the Passio sancti Sebastiani, in which it was recounted that the martyrs Marcus and Marcellianus were deposited « in loco qui dicitur ad arenas, quia cryptae arenarum illic erant, ex quibus urbis moenia struebantur ». The theory was opposed by Fr. Marchi, who, from observing the rocks composing the Roman soil, became convinced that the catacombs had been excavated solely by the Christians, not for the purpose of extracting building material, but only as burial places. Indeed, only exceptionally are parts of earlier arenaria found in Rome being used for Christian burials, as in the catacombs of Priscilla, Domitilla, and Commodilla (B. Bagatti, Il cimitero di Commodilla, Vatican City 1936, p. 35 and fig. 22). The galleries of the arenaria were much more broadly excavated, at times with rounded walls, usually approximately 2.20 m wide and 2.30 m high, whereas the galleries excavated by the Christians are much narrower and have vertical walls.
Outside Rome, too, the cemetery known as S. Gennaro dei Poveri at Capodimonte in Naples, and that known as S. Maria della Stella at Albano, make use of galleries previously excavated for the extraction of building materials.