EXTINCT ORDERS OF REPTILES. 447 



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- 

 tebrcB 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 

 vertebra 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. 

 The limbs agree with those of the Ichthyosauri in being in the 

 form of swimming-paddles (fig. 176), but differ in not possessing 

 aay supernumerary marginal ossicles. A pectoral arch, formed 

 of two clavicles and an interclavicle (episternum) appears to 

 have been sometimes, if not always, present. The teeth were 

 simple, and were inserted into distinct sockets, and not lodged 

 in a common groove. 



The most familiar and typical member of the Sauropterygia 

 \% \!a& Plesiosaurus (fig. 176), a gigantic marine reptile, chiefly 

 characteristic of the Ijas and Oolites. As regards the habits 

 of the Plesiosaurus, Dr Conybeare arrives at the following con- 

 clusions : — " That it was aquatic 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 ex- 

 tremities to those of the Turtles may lead us to conjecture ; its 



