DINOSAURIAN REPTILES. 515 



Fig. 451) in which the jaws are much narrower, is over four 

 and a half metres (14 feet) long. It inhabits the rivers of 

 Florida where it is very rare, and also the West Indies and 

 South America. The cayman of Guiana belongs to a dis- 

 tinct genus, Caiman, and is characteristic of the rivers of 

 tropical South America. 



Order 10. Dinosauria. We now come to reptiles which 

 have more decided affinities as regards their skeleton (the 

 only parts preserved to us) to the birds, especially the os- 

 triches, than any reptiles yet mentioned ; while the Dino- 

 saurs were genuine reptiles, in the pelvis and hind limbs, 

 including the feet, they approached the birds. This is seen 

 especially in the ischium, which is long, slender, and inclined 

 backwards as in birds. In the hind limbs the resemblance 

 to birds is seen ; among other points, in the ascending pro- 

 cess of the astragalus, in the position of the farther (distal) 

 end of the fibula, and in their having only three functional 

 toes. The fore limbs were shorter and smaller than the 

 hind extremities, sometimes remarkably so. Moreover, the 

 limb-bones, vertebrae, and their processes were sometimes 

 hollow ; the sacrum consisted of four or five consolidated 

 vertebrae, in this respect anticipating the birds and mam- 

 mals. They walked with a free step, like quadrupeds, 

 instead of crawling like reptiles ; some walked on the hind 

 legs alone, making a three-toed footprint, occasionally 

 putting down the forefoot, like the kangaroo. The lar- 

 gest Dinosaurs were the Iguanodon, which was from ten 

 to sixteen metres (30-50 feet) in length, and the Cama- 

 rasaurus (Atlantosaurus) which was about twenty-seven 

 metres (80 feet) in length. The Cetiosaurus had a length of 

 from twenty to twenty-three metres (60-70 feet). The Ha- 

 drosaurus stood on its ponderous hind legs, with a stature of 

 over eight metres (25 feet). These were bulky, inoffensive, 

 herbivorous monsters, able to rise up on their hind feet and 

 browse on the tops of trees ; their undue increase was 

 prevented by carnivorous forms like Lcelaps, which was an 

 active, possibly warm-blooded Dinosaur, with light, hollow 

 bones, large claws, and serrate, conical teeth. It stood six 

 metres (18 feet) high, and could leap a distance of ten 

 metres through the air. (Cope.) 



