186 THE STORY OF REPTILE LIFE. 



mands. The Iguanodons seem to show that 

 at least all but the very largest may have lived 

 on land.- Of the reptiles now in question, four 

 or five species are known, remains of which 

 have been found in this country, though not in 

 such completeness as in Belgium. Of these two 

 species, the smaller Iguanodon mantelli was about 

 equal in size to the extinct Giant Sloth, Mega- 

 therium. Now the latter, one of the Mam- 

 malia, was most emphatically a forest-haunting 

 species, and we may well imagine that Man- 

 tell's Iguanodon, which is known to have been 

 herbivorous, lived in a similar habitat. This 

 being so, it seems more reasonable to suppose 

 that the still larger species, Iguanodon bernissar- 

 tensis, which was some thirty feet long from the tip 

 of the snout to the tip of the tail, was, in spite 

 of its great size, also a dweller on land. Other- 

 wise, we must suppose either that the aquatic 

 life was adopted after the size of the smaller 

 species had been surpassed, or that, though 

 living in environments totally different, they 

 acquired a form practically indistinguishable 

 save in point of size. Between Iguanodon and 

 Diplodocus there is an interesting point of 

 difference in the matter of the dentition, for 

 whereas in the latter only the front of the jaws 

 bear teeth, and these of a peculiarly slender 

 character, in the former the front of the jaws 

 were toothless and ensheathed in horn, whilst 

 the sides of the jaws bore teeth in closely serried 

 ranks. From their close resemblance to the teeth 

 of the living Iguanas this giant derives its name, 

 which being translated means Iguana toothed. 



