A HISTORY OF KENT stone belong to this species. All the known specimens indicate imma- ture individuals. Among the fish-lizards, or ichthyosaurians, the common Cretaceous species Ichthyosaurus campylodon is represented in the county by teeth and jaws from the Lower Chalk of Dover and the Chalk-marl of Folkestone, as well perhaps as from the Gault of the latter place. Of the plesio- saurians, another group of marine saurians, differing from the ichthyo- saurians, among other features, by the structure of the skeleton of the paddles, the long-necked Cretaceous genus Cimoliosaurus is represented by C. sniithi in the Upper Chalk of Burham, and possibly also in the Folkestone Gault. Large fluted teeth from the Chalk of Charing, Cuxton, Dover and Hailing, described under the name of Polyptychodon interruptus, indicate a huge short-necked member of the same order, the type specimens of which appear to be Kentish. Other teeth from the Chalk of the county have been referred to the closely allied, if not identical, P. contiriuus, which is typically of Lower Greensand age. The fishes from the Kentish Chalk form a list of almost appalling length, including over seventy species. The beautifully corrugated and pustulated crushing teeth of the Cretaceous rays of the genus Ptychodus are not uncommonly met with (sometimes in associated sets) in the chalk pits of the county, where no less than seven species are repre- sented. These are P. mammillaris, from Chatham, Cuxton, Dover, Hailing, Maidstone and Rochester ; P. rugosus, from Chatham, Dover, Greenhithe and Rochester ; P. oweni, from Snodland and else- where ; P. decurrens, from Burham, Dover, Hailing and Maidstone ; P. polygyrus, from Bromley, Burham, Charlton, Gravesend, Hailing, Maidstone and Northfleet ; P. multistriatus, from Burham, Dover, Maid- stone and elsewhere ; and P. latissimus, from Maidstone and other local- ities. Of these only the third and sixth were named on the evidence of Kentish specimens. Of the comb-toothed sharks remains of Notidanus microdon occur at Burham, Charing and Maidstone. In the group of sharks {Cestra- ciontidce) allied to the existing Port Jackson species, so well known for its beautiful crushing teeth, the existing genus is represented by Cestracion canaliculatus at Bromley, and C. rugosus at Charing, Dover and Maid- stone, as well as in the Folkestone Gault. Another (extinct) generic type is represented in the Dover Chalk by Synechodus illingworthi, and in that of Dover, Gravesend and Margate by S. dubrisiensis ; the latter species being named on the evidence of Kentish specimens. Two species of dog-fish {Scyllium antiquum and S. dubium) are severally founded upon single specimens, the one from Dover and the other from Burham. Two species of beaked sharks (a genus still surviving in Japanese waters), namely Scapanorhynchus rhaphiodon and S. subu/atus, are known from the Chalk of the county, the latter being recorded from Charing, Dover, Greenhithe and Hailing. Of far greater local interest is however Catitio- scyllium decipiens, an extinct genus and species of shark, with striated teeth, known only by part of the skeleton from the Lower Chalk of
