On the opposite side of the Appian Way, in a vineyard, is the Catacomb of Pretextatus, which is almost as extensive as that of St. Calixtus, and hardly less interesting.  It is especially remarkable for a large square crypt, inlaid with brick and plaster, and covered with very fine frescoes and arabesques of birds and foliage.  The bodies of St. Januarius, Agapetus, and Felicissimus, who suffered martyrdom in the year 162, were interred in this Catacomb; and two churches, at a subsequent period, were erected over it in honour of the three saints who suffered martyrdom with St. Caecilia.  Recent explorations have brought to light, in a separate part of this Catacomb, curious paintings and inscriptions which have been referred to the mysteries of Mithras—­an Oriental worship of the Sun—­introduced into Rome about a century before Christ, and which was celebrated in caves.  When Christianity became popular, and was threatening the overthrow of polytheism, an attempt was made to counteract its influence in the reign of Alexander Severus, who himself came from the East, by organising this worship.  The two systems of religion became, therefore, mixed up together for a while; and hence it is not uncommon to find in pagan sepulchres symbols and arrangements of a Christian character, and in Christian Catacombs Mithraic features.  The funeral monuments of those who were converted to Christianity in the earliest ages of the Church indicated the transition between the two religions.  We find upon their tombs pagan symbols, which ceased to be identified with pagan worship, and became mere conventional ornaments.  We have other evidences along the Appian Way of the eclectic revival of paganism at this time.  When alluding to the classic stream of the Almo, I spoke of the associations of the worship of Cybele.  This naturalistic cult was introduced from Phrygia, and its orgiastic rites and nameless infamies had a horrible fascination for an age of decaying faith.  And not far from the mounds of the Horatii and Curiatii there is a monument, probably of the age of Trajan, with a bas-relief portrait, dedicated to the memory of one Usia Prima, a priestess of Isis; this worship, with its painful initiations and splendid ritual, being imported from Egypt in the second century.  But although this Neo-paganism appealed more to the passions of men than the sunny humanistic worship of older times, and for a time inspired the most frenzied enthusiasm, it failed utterly to resuscitate the decaying corpse of the old religion.  Great Pan was hopelessly dead!

At a short distance on the same side of the road is the Catacomb of Sts.  Nereus and Achilles, which contained the remains of these saints, and are interesting to us as the most ancient Christian cemetery in the world.  The masonry of the vestibule is in the best style of Roman brickwork; and the frescoes on its walls, representing Christ and His apostles, the Good Shepherd, Orpheus, Elijah, etc., indicate