120 FOOTPRINTS OF A DINOSAUR. 



of their bodies, which is in contrast to their comparatively feeble 

 cerebral development. The centra of the dorsal, and frequently of the 

 sacral vertebrae, enclose cavities of considerable dimensions divided 

 into two lateral chambers, separated by a median longitudinal wall, 

 which, in Sir Richard Owen's opinion, was supplied with cartilage ; 

 but, in Professor Marsh's, was filled with air. Under either view 

 there was a provision to aid the progression of the animal, whose 

 body was 60 or 70 feet long. In addition to this the medullary 

 canal of the sacral region was two or three times larger than the 

 brain cavity. The bones of the limbs, as is the case with all 

 reptilians, are solid and destitute of a medullary channel, this 

 provision having probably some relation to the enormous develop- 

 ment of the tail. The nerves, although slightly differing in 

 structure from the brain, keep up a mysterious connection between 

 the head and every part of the body. 



The discovered remains of European Sauropods are confined to 

 isolated vertebrae, bones, and teeth. In this county they have only 

 been found in the Kimmeridge clay of Weymouth and Kimmeridge. 

 Dinosaurian remains have been principally found in the Triassic, 

 Jurassic, and Cretaceous beds of Europe and North America. 

 Fragmentary remains have been found principally in the Triassic 

 and Cretaceous beds of the East Indies and in the Trias of South 

 Africa. They are absent in South America and Australia. 



The ponderous bodies of dinosaurs were supported by a massive 

 pair of hind-limbs, upon which they walked in an upright position, 

 and probably used their short fore-limbs for bringing the boughs of 

 the trees on which they fed to their mouth and for swimming, 

 aided by their powerful tail, which attained additional strength by 

 a strong muscle attached to the middle trochanter. The vertebral 

 column was strengthened by five or six anchylosed sacral vertebra. 

 The Iguanodon had a smooth and scaleless skin. 



Some dinosaurs were furnished with dermal plates or scutes, 

 to which in some cases formidable spines were attached for 

 protection from the attacks of enemies such as the Megalosaurus. 

 The dentine system of the herbivorous dinosaurs is very varied ; 



