386 



DmOSAURIA 



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» Pbedentata.* 



Large herbivorous quadripedal or bipedal Dinosaurs, with an edentu- 

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

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

 compressed with serrated anterior and posterior cutting edges and are 



Fia. 212. — Iguanodon bernissartensis ; restoration of skeklou by Marsh x ^. 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 armoiu* is present or absent. 

 Jurassic and Cretaceous. 



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

 hollow limb bones. U. Jiu-a and Cretaceous. Iguanodon Mantel! (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 7. 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. 



