24 



DISTRIBUTION OF ORGANIC REMAINS 



preserved ; and the bones, scales, teeth, and vertebrae are met with, 

 occasionally, in almost all the strata that contain fossil shells, whether 

 secondary or tertiary. Many of the species bear a close resemblance 

 to species at present existing, either in the ocean or in rivers. 



The bones and entire skeletons of reptiles, allied to the saurian or 

 lizard class, occur in the lower part of the secondary strata, and are 

 very abundant in a dark argillaceous limestone called lias, and in 

 the beds of clay that are over it. These animals are, many of them, 

 different from any known existing genera : they were inhabitants of 

 the ocean, and furnished with paddles instead of feet.^ In the up- 

 per secondary strata, between the lias and chalk, the remains of oth- 

 er saurian animals, closely allied to living species of crocodiles and 

 lizards, are fully developed : they had feet, and were evidently am- 

 phibious. Of the saurin animals in this series, that called the igua- 

 nodon, discovered by Mr. Mantell, near Cuckfield, in Sussex, is the 

 most remarkable for its size ; the length exceeding eighty feet, and 

 the thickness of the body being equal to that of the elephant. It is 

 supposed to have been herbivorous. It closely resembles, in struct- 

 ure, the iguana, a native of America and the West Indies. 



The fossil remains of birds are so rare, that their occurrence, in 

 any of the regular strata, was long considered doubtful. The bones, 

 recently discovered in some of the English secondary strata, suppo- 

 sed at first to be those of birds, belong to species of flying lizards. 

 Bones of birds are, however, found in some of the tertiary strata, par- 

 ticularly in the gypsum near Paris. 



Vertebrated animals of the highest class, the mammalia, occur in 

 the tertiary strata, and in ancient beds of gravel and clay. Cetace- 

 ous animals, allied to the whale and seal, have been found in some of 

 the tertiary strata ; but they are by no means common. The bones 

 of herbivorous land quadrupeds occur in the upper part of the tertia- 

 ry beds, or what may be regarded as the latest geological forma- 

 tions : they are, more frequently, found in beds of clay and gravel 

 than in the solid strata. Cuvier has ascertained the existence of fos- 

 sil bones belonging to about seventy species of mammiferous quadru- 

 peds, in the tertiary strata near Paris. Nearly forty of these are of 



* The ichthyosaurus, or fish lizard, had an organisation intermediate between 

 that of a lizard and a flsh: its paddles were long, broad, and flat, to enable it to 

 move rapidly through the water : the orbits of the eyes are enormously large. 

 Four species have been ascertained ; some are of immense size. The Plesiosau- 

 rus, another genus more nearly approaching the organisation of the lizard, is dis- 

 tinguished from all oviparous quadrupeds by the form of its neck, which is longer 

 than its body, and is composed of no less than thirty vertebrge, exceeding in num- 

 ber those in the neck of the swan. This animal is supposed to have swum on the 

 water, with its neck arched to dart on its prey. The Testudo ferox, living in the 

 rivers in Florida, is somewhat similarly constructed: it hides itself in reeds, and 

 darts out its head, suddenly, to seize birds and other animals. There are five spe- 

 cies of the Plesiosaurus, some of them were more than twenty feet long. Remains 

 of flying lizards have been discovered in a fossil state in Germany, and very re- 

 cently in Oxfordshire and Dorsetshire. 



