DINOSAURTA OR DINOSAURS. 221 



lids, and the ear with an external opening. The Saurians 

 as here defined include the huge fossil Dinosaurs, the 

 Crocodiles, etc., the Lizards, the fossil Ichthyosaurs, etc., 

 the Pterodactyls, etc. The name Sauria comes from the 

 Greek sauros, a lizard. 



But the differences exhibited by these various forms of 

 saurians lead zoologists to recognize them as representa- 

 tives of distinct orders ; and they are accordingly so 

 treated in this book. 



The Dinosaurs are an order of reptiles which we know 

 only by their fossil remains. They are of gigantic size, 

 and they combine in their structure reptilian, bird-like, 

 and mammalian characteristics. The name is derived from 

 the Greek deinos, terrible, and sauros, a lizard. Their 

 cervical vertebrae are convex before and concave behind, 

 as in mammals ; their sacrum consists of four or five ver- 

 tebrae, as in mammals ; the long bones have a medullary 

 cavity ; and the hind feet are more or less bird-like. And 

 these animals often walked on their hind feet, as if 

 bipeds. 



To this order belong the Iguanodon, an herbivorous 

 dinosaur of the Jurassic period, an animal of vast bulk, 

 and having a length of twenty to forty feet or more. 

 Here also belong the Hadrosaurus, Ilylcesaurus, and the 

 Megalosaurus ; the last a gigantic carnivorous Jurassic 

 reptile more bulky than an elephant, and thirty feet in 

 length. 



Many of the bird-like tracks of the Connecticut valley 

 are regarded as those of huge dinosaurs. These tracks 

 occur on the successive layers of sandstone of Triassic or 

 Jurassic age ; and they are found at various places, from 

 the northern portion of Massachusetts to Long Island 

 Sound. 



