312 PALEONTOLOGY. 



miliani, from the cretaceous beds of North America, and a 

 smaller species, M. gracilis, from the chalk of Sussex * The 

 Leiodon anceps of the Norfolk chalk was a nearly allied marine 

 Lacertian.j" 



Many small terrestrial Lacertians have left their remains 

 in European tertiary formations. 



Order XL — Ophidia. 



(Sloiv-ivorms, Serpents. ) 



Char. — Vertebrae very numerous, procoelian, with a single 

 transverse process on each side, and single-headed hol- 

 low ribs ; no sacrum ; no visible limbs. 



The order Ophidia, as it is characterized in the system of 

 Cuvier, requires to be divided into two sections, according to 

 the nature of the food, and the consequent modification of the 

 jaws and teeth. Certain species, which subsist on worms, 

 insects, and other small invertebrate animals, have the tym- 

 panic pedicle of the lower jaw immediately and immovably 

 articulated to the walls of the cranium. The lateral branches 

 of the lower jaw are fixed together at the symphysis, and are 

 opposed by the usual vertical movement to a similarly com- 

 plete maxillary arch above ; these belong to the genera 

 Amphisbwna andiAnguis of Linnseus, the latter represented by 

 our common slow-worm. The rest of the Ophidians, including 

 the ordinary serpents and constrictors, which form the typical 

 members, and by far the greatest proportion, of the order, prey 

 upon living animals of frequently much greater diameter than 

 their own ; and the maxillary apparatus is conformably and 

 peculiarly modified to permit of the requisite distension of 

 the soft parts surrounding the mouth, and the transmission of 

 their prey to the digestive cavity. All the ophidian fossils 

 hitherto determined belong to the latter typical group. 



* Op. cit,, p. 185, pis. 1, 2, 9. f Op. cit., p. 195, pi. 10. 



