Some additional discoveries were described by Marc Antonio Boldetti in his Osservazioni, published in 1720; but, writing in the interests of the Roman Church with an apologetic, not a scientific object, truth was made to bend to polemics, and little addition to our knowledge of the catacombs is to be gained from his otherwise important work.
Felix and Adauctus, discovered by Boldetti and afterwards choked up with ruins, was cleared again: the crypt, begun by Damasus and enlarged by Siricius, contains frescoes of the 6th-7th centuries.
A good plan of the catacombs at Albano (at the 15th milestone of the Appian way), discovered by Boldetti and described by De Rossi, has been published by Marucchi (Nuovo Bulletino di archeologia cristiana, 1902, pp. 89 ff.).
Among the older works are: Bosio, Roma sotterranea, Severano's edition (1632), and Aringhi's edition (1651); Boldetti, Osservazioni sopra i Cmiteri dei santi martini (Rome, 1720); Bottari, Sculture e pitture sagre, &c. (Rome, 1 7371 754); Seroux d'Agincourt, Histoire de l'art par les monuments (Paris, 1823; German ed., 1840); G.