444 MESOZOIC TIME. 



811) had a long, snake-like neck, consisting of twenty to forty verte- 

 brae, a small head, short body, paddles, and biconcave vertebra? dif- 

 fering little in length and breadth. P. dolichodeirus (Fig. 809) was 

 25 to 30 feet long. P. macrocephalus is represented in Fig. 811, just 

 as it lay in the rocks. The British rocks of the Jurassic and Creta- 

 ceous periods have afforded sixteen species of Plesiosaurs ; and 

 twenty-one, in all, are known, of which twelve were found in the Lias, 

 and seven in the Oolyte. The Pliosaurs were other swimming Sau- 

 rians, near tbe Plesiosaur: some individuals were thirty to forty feet 

 long. Remains of more than fifty species of Enaliosaurs have been 

 found in the Jurassic rocks. 



(2.) Crocodtlians. — Many of the Crocodilians were of the Teleo- 

 saur type, having slender jaws like the Gavial, but biconcave verte- 



Fig. 812. 



Mystriosaurus Tiedmanni. 



bra?, — the latter a mark of both antiquity and inferiority. Fig. 812 

 represents the skull of one of these species, the Mystriosaur. 



Another and larger Crocodilian was the Cetiosaur, from the Oolyte, 

 an animal at least fifty feet in length, " not less than ten feet in height 

 when standing, and of a bulk in proportion," and " unmatched in 

 magnitude and physical strength by any of the largest inhabitants of 

 the Mesozoic land or sea." (J. Phillips.) One of the fossil femurs 

 (thigh-bones) is 64 inches long, nearly a foot in diameter at middle, 

 and 20f inches at the upper extremity. The food was probably 

 vegetable. The caudal vertebrae were biconcave, while the dorsal 

 were convexo-concave. Cetiosaurian remains occur in the Oolyte, 

 from the Lower beds to the Wealden. 



(3.) Dinosaurs. — Still other famous Crocodile-like animals were 

 the Megcdosaurs, carnivorous Reptiles, whose remains occur in the 

 Lias, Oolyte, and Wealden. M. BucMandi is the species best known. 

 It was twenty-five or thirty feet long, with the hind limbs twice the 

 longer and stouter. It waded in the waters, or prowled over the land, 

 moving about — " not as a ground-crawler, like the Alligator, but 

 with free steps, and chiefly, if not solely, on the hind limbs, claiming 

 thus a curious analogy, if not some degree of affinity, with the 

 Ostrich." (J. Phillips.) It had a few large teeth, with sharp crenu- 

 lated edges.. The limb bones seem to have been hollow, — one of its 

 bird-like characteristics, — while the hind feet were probably three- 



