FOOTPRINTS OF A DINOSAUR. 121 



the tooth of the Iguanodon is a remarkable contrivance for tearing 

 and cutting tough vegetable food, such as is found with its 

 remains ; it bears a remarkable resemblance to that of the living 

 Iguana in its blade-like form and serrated edges. It is spathulate, 

 the crown compressed, with sharp, serrated cutting edges, which 

 extended on either side downwards from the top to the broadest 

 portion. To counteract the wear and tear of the edges the exterior 

 part of the tooth is furnished with a plate of thin enamel, 

 similar to the incisors of Rodents, and as the softer material 

 of the tooth was worn away more readily than the enamel, an 

 oblique section of the crown was perpetually maintained with a 

 sharp cutting edge in front. The serratures ceased at the broadest 

 diameter of the tooth, below which they would have been useless 

 for cutting purposes. The premaxillse are destitute of teeth. 

 The mouth was probably furnished with a beak, the lower man- 

 dible hollowed out like a parrot's. From the conditions of the 

 Bernissart deposit it may be inferred that the iguanodon was 

 aquatic, frequenting marshes and banks of rivers, more so 

 than the living crocodile. Eeing subject to the attacks of enemies 

 when feeding among the luxuriant vegetation of tree-ferns and 

 other cryptogams, it could better observe their approach in an 

 upright position, by which the wider extent of view was obtained, 

 and not only could more easily defend itself with its powerful short 

 fore feet, but inflict serious wounds with its strong and sharp 

 spurs. Its tail would give the body additional balancing support 

 when erect, in which position it could more easily regain the 

 water, than when threading its long and ponderous body through 

 the tangled vegetation on all fours. 



It only remains now to consider to which dinosaur we may 

 assign the foot-tracks on these Purbeck slabs. There are eeven to 

 choose from 



1 Megalosaurus. 5 Iguanodon. 



2 Cetiosaurus. 6 Hypsilophodon. 



3 Pelorosaurus. 7 Ornithopsis* 



4 Polacanthus, 



