370 REPTILIA. 



In 1 86 1 Professor Marsh discovered in the Coal-measures 

 of Nova Scotia two large amphicoelous vertebrae, which he 

 described under the name of Eosaumis Acadiensis. These 

 vertebras (fig. 320) are of very large size (about two and a half 

 inches in diameter), and they are deeply excavated at both 

 ends. They are regarded by Professor Marsh as indicating 

 the existence in the later Carboniferous period of a gigantic 

 reptile allied to Ichthyosaurus. By Huxley, however, it is 

 believed that these remains may truly belong to some large 

 Labyrinthodont. 



In the biconcave vertebrae and probable presence of a ver- 

 tical tail-fin, the Ichthyosaurus approaches the true Fishes. 

 There is, however, no doubt as to the fact that the animal 

 was strictly an air-breather, and its reptilian characters cannot 

 be questioned, at the same time that the conformation of the 

 limbs is decidedly Cetacean in many respects. Much has 

 been gathered from various sources as to the habits of the 

 Ichthyosaurus, and its history is one of great interest. From 

 the researches of Buckland, Conybeare, and Owen, the fol- 

 lowing facts appear to be pretty well established : That the 

 Ichthyosauri kept chiefly to open waters may be inferred from 

 their strong and well-developed swimming-apparatus. That 

 they occasionally had recourse to the shore, and crawled upon 

 the beach, may be safely inferred from the presence of a strong 

 and well-developed bony arch, supporting the fore-limbs, and 

 closely resembling in structure the scapular arch of the Orni- 

 thorhynchus or Duck-mole of Australia. That they lived in 

 stormy seas,, or were in the habit of diving to considerable 

 depths, is shown by the presence of a ring of bony plates in 

 the sclerotic, protecting the eye from injury or pressure. That 

 they possessed extraordinary powers of vision, especially in 

 the dusk, is certain from the size of the pupil, and from the 

 enormous width of the orbits. That they were carnivorous 

 and predatory in the highest degree is shown by the wide 

 mouth, the long jaws, and the numerous, powerful, and pointed 

 teeth. This is proved, also, by an examination of their petri- 

 fied droppings, which are known to geologists as " coprolites," 

 and which contain numerous fragments of the scales and bones 

 of the Ganoid fishes which inhabited the same seas. 



ORDER VI. SAUROPTERYGIA, Owen ( = Plesiosauria, Huxley). 

 This order of extinct reptiles, of which the well-known Ple- 

 siosaurus may be taken as the type, is characterised by the 

 following peculiarities : 



The body, as far as is known, was naked, and not furnished 

 with any horny or bony exoskeleton. The bodies of the ver- 



