DIN0SAU1UA 265 



skiii was defended by subcircular bony scales. The length of 

 the Hylseosaur may have been 25 feet. 



Genus Iguanodon, Mtll. — Remains of the large herbivorous 

 reptiles of this genus have been found in Wealden and neoco- 

 mian (greensand) strata. Femora, four feet in length, showing 

 the third inner trochanter, have been discovered. The sacrum 

 included five, and in old animals six, vertebrae ; the claw-bones 

 are broad, fiat, and obtuse. There were only three well- 

 developed toes on the hind foot ; and singular large tridactyle 

 impressions, discovered by Beccles in the Wealden at Hastings, 

 have been conjectured to have been made by the Iguanodon. 



With vertebra j , subconcave at both articular extremities, 

 having, in the dorsal region, lofty and expanded neural arches, 

 and doubly articulated ribs, and characterized in the sacral 

 region by their unusual number and complication of structure ; 

 with a Lacertian pectoral arch, and unusually large bones of 

 the hind limbs, excavated by large medullary cavities, and 

 adapted for terrestrial progression ; — the Iguanodon was distin- 

 guished by teeth, resembling in shape those of the Iguana, but 

 in structure differing from the teeth of that and every other 

 known reptile, and unecmivocally indicating the former exis- 

 tence in the Dinosaurian order of a gigantic representative of 

 the small group of living lizards which subsist on vegetable 

 substances. 



The important difference which the fossil teeth presented 

 in the form of their grinding surface was pointed out by 

 Cuvier,* of whose description Dr. Mantell adopted a condensed 

 view in his Illustrations of the Geology of Sussex, 4 to, 1827, 

 p. 72. The combination of this dental distinction with the 

 vertebral and costal characters, which prove the Iguanodon not 

 to have belonged to the same group of Saurians as that which 

 includes the Iguana and other modern lizards, rendered it 

 highly desirable to ascertain by the improved modes of invest i - 

 ; semens Fostiles, 1824, vol. v.. pi. ii.. \>. 351. 



