Page:VCH Norfolk 1.djvu/67

 PALAEONTOLOGY granlandica, Natica catena, N. clausa, and Paludina media. A lamp- shell, Rhynchonella psittacea, is of occasional occurrence. Passing from the Tertiary to the Secondary deposits, the most interesting vertebrate remains from the Norfolk Chalk are teeth of Liodon anceps, a large marine lizard-like reptile allied to the well-known Mosasaurus of the Upper Cretaceous beds of Belgium. Certain other teeth of the same general type, as well perhaps as vertebrse, may indicate a species of the last-named genus in the Chalk of the county. Vertebrae from the White Chalk have been referred to Ichthyosaurus campylodon, and a single tooth of the same genus from the Red Chalk of Hunstanton, preserved in the Woodwardian Museum, Cambridge, has been made the type of an undescribed species, under the name of /. angustideus. Of the cretaceous fishes found in the county, the following are the more important. Firstly, we have a species described as Ccelorhynchus cretaceus, the exact affinity of which is still uncertain. Teeth of the chimsroid Edaphodon sedgwicki occur both in the Upper Chalk of Norwich and in the Red Chalk of Hunstanton. A tooth in the British Museum from the Upper Chalk of Norwich indicates a ray of the genus Squatina ; and other teeth from the Whittington Chalk in the same collection are referable to the pavement-toothed ray known as Ptychodus decurrens. From the Chalk of Swaffham and Norwich have been obtained teeth of a comb-toothed shark, Notidanus mkrodon ; and a species of pavement-toothed shark, referable to the existing Australian genus Cestracion, also occurs in the Norwich Chalk, as well as one pertaining to the extinct genus Synechodus. Of sharks with a more normal type of dentition, the following are represented in the Chalk of the county, viz. : Scapanorhynchus rhaphiodon, S. subulatus, Lamna appendiculata, L. crassa, Corax affinis, and C. pristodontus. From the narrow strip of Kimeridge Clay near Downham Market have been obtained the jaws of a peculiar species of ganoid fish which has been named Caturus suchoides, this unique specimen being in the British Museum. The invertebrate remains from the cretaceous rocks of the county call, as a rule, for no special notice, since they are for the most part identical with those from other districts. An exception must, however, be made in favour of the vertical columns of enormous vase-shaped flints met with at Horstead and certain other quarries in the county, for which the Irish vernacular name paramoudra has been adopted. These flints, which vary from two to five feet in height, have been formed by the deposition of siliceous matter on large sponges somewhat resembling the modern Neptune's-cup sponge [Poterium patera), as they gradually became buried in the chalk ooze. As one individual became buried, another grew in its place on the ocean floor, thus giving rise to the vertical columns in which the paramoudras occur. Some of these flints are pear-shaped rather than vase-shaped, and are hollow only in the centre. Of molluscs, the commonest in the Chalk at Norwich are two lamp-shells, Terebratula carnea and Rhynchonella plicatilis. 37