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 



