722 GEOLOGY. 



Nile." The teeth of the ichthyosaurus, in some instances amounting to 180, and the length 

 of the jaws to more than six feet, qualified it for predacious habits, its food being fishes 

 and the young of its own species. A single paddle of the four with which the animal was 

 furnished sometimes contains more than a hundred bones, giving it great elasticity and 

 power, and enabling it to proceed at a rapid rate through the water. The eye was 

 mormously large, the orbital cavity, in one species, being fourteen inches in its longest 

 direction. The eye also had a peculiar construction, to make it operate both like a 

 telescope and a microscope, so that the animal could descry its prey by night as well as 

 day, and at great depths in the water. This fish-like lizard in some degree answers to 

 the words of Milton, 



" With head uplift above the waves, and eyes 



That sparkling blazed, his other parts besides, 



Prone on the flood, extended long and large, 



Lay floating, many a rood, in bulk as huge 



As whom the fables name of monstrous size, 



Titanian, or earth-born, that warred on Jove. 



Briarchus, or Typhon, whom the den 



By ancient Tarsus held, or that sea beast 



Leviathan, which God of all his works 



Created hugest that swam the ocean stream." 



The ichthyosaurus was an air-breathing, cold-blooded, and carnivorous inhabitant of 

 the ocean, probably haunting principally its creeks and estuaries, fitted by its formidable 

 jaws and teeth, its rapid motion and power of vision, to be the scourge and tyrant of the 

 existing seas of its era, keeping the multiplication of the species of other animals within 

 proper limits. Though essentially marine, and admirably adapted by its organisation to 

 cut the waves, certain peculiarities of structure have induced the opinion that the anterior 

 paddles might be subservient to locomotion not only in the water, but on land. Professor 

 Owen thinks it very conceivable that the ichthyosauri, like the existing crocodiles, may 

 have come ashore to sleep, or resorted thither to deposit their eggs, supposing them to 

 have been oviparous, as the sum of the analogies deducible from their osseous texture 

 would indicate. The remains of these animals are found through the oolite, and in the 

 lower beds of the chalk, but the lias is especially their sepulchre. They occur in great 

 abundance in England, at Barrow-on-Soar, in Leicestershire, in the valley of the Avon, 

 between Bath and Bristol, and on the coast of Dorsetshire, where the cliffs appear to be 

 inexhaustible quarries of them. 



Another marine reptile appears in the lias, which received its name of Plesiosaurus, 

 from Mr. Conybeare, signifying akin to the lizard, from its more closely resembling 

 animals of this genus than fishes, especially in the character of the vertebra. A similar 

 remarkable combination of forms appears in this animal to that which distinguishes its 

 preceding congener, the head of a lizard, the teeth of a crocodile, a neck resembling the 

 body of a serpent, the trunk and tail of an ordinary quadruped, the ribs of a chameleon, 

 and the paddles of a whale. Its most striking feature is the great length of the neck, 

 which has from 30 to 40 vertebrae, a larger number than in any other known animal, 

 those of living reptiles varying from 3 to 6, and those of birds from 9 to 23. It has been 

 therefore correctly compared to a serpent, threaded through the body of a turtle. " That 

 it was aquatic," remarks Mr. Conybeare, " is evident from the form of its paddles ; that it 

 was marine is almost equally so, from the remains with which it is universally associated ; 

 that it may have occasionally visited the shore, the resemblance of its extremities to those 

 of the turtle may lead us to conjecture ; its motion, however, must have been very 

 awkward on land ; its long neck must have impeded ks progress through the water, 



