DINOSAURIA. 209 



apposed to their lower end. The first and fifth digits are entirely wanting 

 in the hind foot, but the three others are very massive with broad hoofs, 

 and the phalangeal formula is 3, 4, 5. The typical species is Claosaurus 

 annectem, known by two tolerably complete skeletons from the Laramie 

 Beds (uppermost Cretaceous) of Wyoming, U.S.A. It is about nine 

 metres in length. 



FIG. 128. 



Claosaurus annectens ; restoration of skeleton by 0. C. Marsh, one-eightieth 

 nat. size. Cretaceous ; Wyoming. 



The armoured Ornithopoda or STEGOSAURIA, as they are 

 often termed range from the Lower Lias to the Cretaceous 

 inclusive in England, and are both Jurassic and Cretaceous in 

 North America. Scelidosaurus, from the Lower Lias of Dorset- 

 shire, is only moderately armoured ; Stegosaurus, from the 

 Jurassic of the United States, and Omosaurus, from the Upper 

 Jurassic (Oxford and Kimmeridge Clays) of England, are 

 provided with great spines and dermal plates ; while Pola- 

 canthus, from the English Wealden, has the lumbar-sacral 

 region completely encased in a continuous shield of fused 

 plates, which press the ilium downwards. The latter is par- 

 ticularly remarkable because the tips of the hindermost ribs in 

 the only known specimen seem to penetrate between the an- 

 terior extension of the ilium and its superincumbent armour, 

 w. 14 



