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 H PALEONTOLOGY ERTFORDSHIRE is a county singularly deficient in interest so far as the palaeontology of vertebrated animals is concerned. Not only does it lack any fauna of extinct vertebrates peculiar to itself, but it is extremely poor in vertebrate remains of any description ; its gravels being generally devoid of the teeth and bones of the larger mammals, while very few remains of the lower vertebrates appear to have been yielded (or at any rate recorded) from the chalk of the county. There is however one very notable exception as regards the fossils of the chalk. This is an imperfect tooth of an iguanodont reptile from the Totternhoe stone near Hitchin described by Mr. E. T. Newton 1 under the provisional designation of Iguanodon hilli. The iguanodons, it may be observed, form a group of gigantic extinct reptiles which walked exclusively on their three-toed hind limbs, and are specially characterized by the peculiar structure of their teeth. These latter have serrated margins and a sculptured external surface, and were adapted for a veget- able diet, wearing down by use after the manner of those of herbivorous mammals. The Hitchin specimen differs somewhat from the teeth of Iguanodon mantelli from the Sussex Wealden in the sculpture of the outer surface, and may possibly indicate a distinct generic type. It is of especial interest as being the most modern iguanodont fossil hitherto found in England ; while it has a local interest on account of being the only vertebrate fossil hitherto described as peculiar to Hertfordshire. If careful collecting of the fossils in the Hertfordshire chalk were undertaken it is probable that examples of many of the commoner kinds of Cretaceous fishes might be obtained. From the chalk of Tring the British Museum possesses seven teeth of the Cretaceous ray, scientifically known as Ptycbodus decurrens ; while the same collection likewise contains a lower median tooth of the allied species, Pt. iatitsimus, from the chalk of Hertford. Ptychodus teeth may be recognized by their quadrangular form and ridged centre ; the margins of each tooth being minutely pustulated. They were arranged so as to form a pavement in the mouth, and were adapted to crush shellfish and crustaceans, like those of modern skates and rays. Four teeth from the London Clay of Hertford preserved in the British Museum belong to a common Cretaceous shark, Odontaspis elegans. A fragmentary bone from the London Clay of Watford has 1 Geo/ogical Magazine, decade iii. vol. viii. p. 49 (1892). 41