EXTINCT ORDERS OF REPTILES. 417 



searches of Buckland, Conybeare, and Owen, the following 

 facts appear to be pretty well established : That the Ichthyo- 

 sauri kept chiefly to open waters may be inferred from their 



Fig. 163. Ichthyosaurus comtnunis. 



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 enor- 

 mous 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 petrified drop- 

 pings, 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, Hux- 

 ley). This order of extinct reptiles, of which the well-known 

 Plesiosaurus 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- 

 tebrae were either flat or only slightly cupped at each end, and 

 the neural arches were anchylosed with the centra, and did not 

 remain distinct during life. The transverse processes of the 

 vertebrae were long, and the anterior trunk-ribs had simple, not 

 bifurcate, heads. No sternum or sternal ribs are known to have 

 existed, but there were false abdominal ribs. The neck in 

 most was greatly elongated, and composed of numerous verte- 

 brae. The sacrum was composed of two vertebrae. The orbits 

 were of large size, and there was a long snout, as in the Ichthyo- 

 sauri, but there was no circle of bony plates in the sclerotic. 



VOL. II. 2 D 



