386 DIXOSAURI A. 



being extremely shortened as in Cetaceans ; cervical vertebrae elongated, 

 15 in number ; 11 dorsals, 4 sacrals and 37 or more caudals ; the neck 

 and tail constitute the greater part of the animal, the head is very small ; 

 chevron bones double, each half with anterior and posterior prolongation ; 

 the curious position of the external nares may suggest aquatic habits, 

 U. Jura, Wyoming and Colorado. 



Order 3. PREDENTATA.* 



^ Large herbivorous quadripedal or bipedal Dinosaurs, with an edentu- 

 lous predentary bone at the front end of the mandible, and a fully ossified 

 brain case. The premaxillae are edentulous. The teeth are laterally 

 compressed with serrated anterior and posterior cutting edges and are 



FIG. 212. Iguanodon bernissartensis; restoration of skeleton by Marsh xJgV Wealden, 

 Bernissart (from Woodward). 



borne by the maxillae and dentaries. The pubis is slender, directed ven- 

 trally, but does not form a symphysis ; there is a slender postpubis 

 directed backwards parallel with the ischium which is also slender and 

 meets its fellow in a ventral symphysis. The limb bones are solid or 

 hollow. The manus has four or five digits, the pes three or four ; the 

 femur has a prominent distal inner (fourth) trochanter, and the astragalus 

 is without an ascending process ; dermal armour is present or absent. 

 Jurassic and Cretaceous. 



Tribe 1. ORNITHOPODA. Unarmoured, bipedal, digitigrade forms, with 

 hollow limb bones. U. Jura and Cretaceous. Iguanodon Mantell (Fig. 

 212), so called from the resemblance of its teeth to those of Iguana, from 

 the Wealden of England, Belgium and Germany, several complete skele- 

 tons of /. bernissartensis about 30 ft. in length have been discovered in the 

 colliery of Bernissart in Belgium about 1,000 feet below the surface. The 



* Also called Orthopoda. 



