Page:VCH Sussex 1.djvu/80

 A HISTORY OF SUSSEX tortoises of this genus are distinguished by the abnormal width of the row of horny shields covering the middle of the back. To a species of an allied genus, Plesiochelys brodiei, typically from the Wealden of the Isle of Wight, is assigned a young shell in the British Museum from the same formation at Hastings ; while fragments of a shell from Cuck- field in the same collection apparently indicate another species of the genus. It should be added that the species to which the names Platemys mantelli and P. dixoni have been applied belong to Hylceochelys belli. Very interesting are certain fragments of a chelonian shell from Cuck- field which have been made the type of a genus and species by the present writer under the name of Archceochelys valdensis ; but they are unfortunately too imperfect for the affinities of the genus to be properly determinated. Of long-necked plesiosaurians two small-sized species are known from the Wealden of the county. One of them, Cimoliosaurus llmno- philus, from Cuckfield, was first described from the Wealden strata of the continent. The second, C. valdensis, which occurs at Cuckfield and in the Wadhurst Clay of Hastings, is peculiar to the county. The comparatively small dimensions of both these saurians are probably due to their being dwellers in brackish instead of salt water. The fossil fishes of the Sussex Wealden are not numerous, although of considerable interest. Among the pavement-toothed sharks allied to the existing Port Jackson species the widely spread genus Hybodus is represented by H. basanus, a species first described from the Wealden of the Isle of Wight, but which also occurs at Hastings, Hollington, Pevensey Bay and in Tilgate Forest. Teeth from Hastings and Tilgate Forest indicate the occurrence of two other species of the same genus in the Wealden of the county. In the allied genus Acrodus the species A. hirudo was named by Agassiz on the evidence of a tooth, now in the British Museum, from Tilgate Forest ; and the same collection also contains a smaller tooth of this species from the Wealden of Telham near Battle. Fin-spines from Tilgate Forest have been made the types of Asteracanthus granulosus, a species of another widely spread genus of the same group of sharks. Among the ganoid fishes, or those whose scales are bony, quad- rangular and highly polished, the button-like teeth of Lepidotus mantelli occur in the Wealden strata of Billingshurst, Brightling, Heathfield, Hastings, Horsham, Tilgate Forest and other localities in the county, often accompanied by scales. In the neighbourhood of Hastings and in Tilgate Forest these teeth are extraordinarily abundant ; they are known to the quarrymen as ' fishes' eyes,' The Wealden species, which also occurs in Germany, was named by Agassiz on the evidence of Mantell's specimens ; many other species of the genus are known from Jurassic and Cretaceous strata. Of the pycnodont ganoids the species Ccelodus mantelli, a member of another widely spread genus, was named by Agassiz from specimens of the dentition collected by Mantell in Tilgate Forest, A second and larger species, C. parallelus, was named