JURASSIC ANIMALS. 



437 



boidal enameled scales, pavement palatal teeth, and persistent note- 

 chord (Fig. 682). 



Reptiles. — The huge reptiles which form the distinguishing feat- 

 ure of this age culminate in the Jurassic period. Their number and 

 variety are so great that we can only select a few from each order for 



Fig. 685. 



Fig. 686. 



Figs. 683-686.— Jurassic Reptiles— Ichthyosaurus and Plesiosanrus : 683.— Ichthyosaurus commu- 

 nis, x y^j. 684. Plesiosaurus dolichodeirus, restored, x ^j. 685. Vertebras of Ichthyosaurus and 

 Section of same, showing structure. 686. Tooth of Ichthyosaurus, natural size. 



description. They were emphatically rulers in every department of 

 Nature — rulers of the sea, of the land, and of the air. We shall treat 

 of them under the three heads thus indicated, viz. : 1. Enaliosaurs 

 (sea-saurians), or rulers of the sea; 2. Dinosaurs (huge saurians), or 

 rulers of the land ; and, 3. Pterosaurs (winged saurians), or rulers of 

 the air. The first were wholly swimming, the second walking, the 

 third flying, saurians. Intermediate between the first and second was a 

 fourth order, the Crocodilians, which both swam and crawled. 



1. Enaliosaurs. — From the immense variety of these we select only 

 two for description as representative genera, viz., Ichthyosaurus and 

 Plesiosaurus (Figs. 683 and 684). 



The Ichthyosaurus (fish-lizard) was a huge animal, in some cases 

 thirty to forty feet in length, with a stout body, short neck, and enor- 

 mous head, sometimes five feet long, and jaws set with large conical, 

 striated teeth, sometimes 200 in number. The enormous eyes, some- 

 times fifteen inches in diameter, were provided with radiating, bony 

 plates (sclerotic bones), as are the eyes of birds and some living and 



