ORDER DINOSAURIA. 



1157 



anchylosed to the tibia, was closely applied to its distal extremity, 

 and thus rendered the structure of the ankle-joint (as in many 

 other members of the order) essentially similar to that of a Bird. 



It may be observed that the inner trochanter of the femur corresponds 

 to the small one found in some Birds, which gives attachment to the 

 femoro-caudal and ischio-femoral muscles, and it is interesting to find, 

 from the observations of M. Dollo, that its form in Ignanodon is that 

 which agrees with the Avian type. 



Igiiaiiodon ranges from the Wealden to the Lower Greensand, 

 and hitherto has only been described from Europe. The two 

 representatives of the typical or Euiguanodont group occur in the 

 Upper Wealden and Lower Greensand, and comprise /. Mantelli, 

 and the larger I. bernissartensis (fig. 1056) ; these two species being 

 also distinguished from one another by the number of the sacral 

 vertebrae, and the contour of the ilium and femur. 



The length of the entire body of the larger /. bernissartensis is esti- 

 mated at about 33 feet. The history of the gradual reconstruction of the 

 skeleton of this genus affords an instructive instance of the results which 

 may be attained by careful and patient study of fragmentary remains. 



Fig. 1059. — Left lateral aspect 01 the skull of Iguanodon bernissartensis ; from the Wealden 

 of Belgium. Much reduced. The anterior aperture is the nares ; the middle one the orbit ; and 

 the posterior the infratemporal fossa. The predentary bone is seen at the extremity of the 

 mandible. (After Dollo.) 



By the labours of the late Dr G. Mantell of Lewes, in the first half of 

 this century, a considerable knowledge was acquired of the greater part 

 of the skeleton, although the structure of the pectoral and pelvic girdles 

 remained a puzzle. The structure of the latter was, however, after more 

 than one ineffectual attempt, finally solved by the labours of Professor 

 Huxley and Mr J. W. Hulke. 



In the Wadhurst Clay, or Lower Wealden, of Sussex, we meet with 

 three species of Iguanodon which connect the preceding typical 



