FOSSIL REPTILES OF DORSET. 35 



fret border of which, denticulate, may have been sheathed with 

 horn as in turtles. The quadrate bone is long and stout. The 

 exterior nares are capacious. The orbits are elliptic in shape, 

 the horizontal diameter exceeding the vertical. Owing to 

 the jaws of all the recovered heads being closed, the inside 

 of the mouth has never as yet come under complete examination ; 

 it has been surmised, however, from the evidence of a few 

 detached and broken fragments, that the internal nares are 

 placed far back in the palate. The fore-limb is half the length 

 of the hind ; the humerus is relatively short ; the manus long in 

 proportion, being one fourth the length of the limb ; the last 

 phalanx of the inner-digit is spur-like ; the metacarpals are 

 narrow and compressed laterally. The sacrum consists of five 

 anchylosed vertebrae. The ilium projects considerably beyond its 

 articulation with the head of the femur, which has an inner 

 trochanter near the centre of the shaft, from which probably 

 originated a set of muscles to strengthen and give motion to its 

 massive tail, and to aid its progress through the water. The taij 

 aided the animal to walk upright, not so much as a support but as a 

 compensatory balance to structural hindrances when on land. Foot- 

 prints of animals have been frequently noticed in the Wealden 

 beds of Sussex, the Isle of Wight, and Swanage as early as 1854. 

 Mr. Beckles named them Ornitlioidichnites, supposing them to be 

 the footprints of birds. He describes them as in pairs or groups, 

 one in advance of the other and uniform in direction, and at an 

 interval of about three feet four inches from each other. The 

 largest was 21 inches long and invariably trifid, the centre toe the 

 longest. Conjectures soon arose that they were foot-prints of the 

 Iguanodon, which are now fully confirmed by M. Dollo, who, 

 after comparing the hind feet of Iguanodon Mantellii with 

 the natural casts preserved by Mr. Beckles, concludes that no other 

 Wealden Dinosaur could have produced these tridactyle impres- 

 sions. The Iguanodon was probably more aquatic than the 

 Crocodile, living in the swampy marshes of the Wealden rivers ; 

 being graminivorous it would have enemies, and be subject to the 



