The Ophidia are not known to occur in any Palaeozoic or Mesozoic deposit The earliest-known traces of any serpent are in the Lower Kaino-zoic rocks, the oldest being the Palaeophis toliapicus of the London Clay of Sheppey. The nearly-allied Palaeophis typhous of the Eocene beds of Bracklesham appears to have been a Boa - constrictor - like snake of about twenty feet in length. Other species of Palaeophis have been described from the Tertiary rocks of the United States, and the genus Dinophis has been formed for the reception of another gigantic constricting serpent from the same formation. In some of the later deposits have been found the poison-fangs of a venomous snake. Upon the whole, however, the Snakes must be looked upon as a comparatively modern group, and not as one of any great geological antiquity.