EVOLUTION, VARIATION AND HEREDITY 



481 



the lumbar region of the spinal cord many times larger than the 

 brain, and presumably to look after the heavy hind limbs and tail. 

 The horned forms are represented by such an animal as Triceratops, 

 in form somewhat like a Rhinoceros, and reaching a length of 20- 



FIG. 176. Restoration of the horned dinosaur Triceratops. Length, 20-25 

 feet. Upper Cretaceous (Lance), western North America. After Lull, 

 from Schuchert's "Historical Geology." 



25 feet. It had a sort of short beak, two large horns over the eyes, 

 one over the nasal region, and a large frill-like collar of bone extending 

 back over the neck. 



In early Jurassic times a remarkable group of flying lizards, 

 the Pterodactyla, arose probably from the same group as the 



FIG. 177. Pterodactyl, Rhamphorhynchus phyllurus. After Lull. 



Omithischia, and persisted until the end of the Cretaceous. They 

 were provided with wings, not produced, as in birds, by the develop- 

 ment of feathers on the fore limb, but by the growth of a membrane 

 stretching from the tips of the enormously elongated fingers back to 

 the toes, and so somewhat similar to the bats of to-day. Their heads 



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