THE GEOLOGICAL RECORD 201 



owing to unfavourable circumstances the connecting links 

 have rarely been preserved. The singular Chelonia (turtles 

 and tortoises) appear fully formed at the end of the Trias or 

 in the earliest Jurassic beds, as do the crocodiles, the aquatic 

 Plesiosaurians and Ichthyosaurians, the flying Pterodactyls, 

 and the huge Dinosaurs. All these have more or less 

 obscure interrelations, and their common ancestors cannot 

 well be older than the Permian, since the preceding Carboni- 

 ferous offered highly favourable conditions for the preserva- 

 tion of the remains of such land animals had they existed. 

 To bring about the modification of some primitive reptile 

 or amphibian into all these varied forms, and especially to 

 bring about such radical changes of structure as to develop 

 truly aerial and truly oceanic reptiles, must, with any reason- 

 able speed of change, have required an enormous lapse of 

 time, yet all these had their origin seemingly during the 

 same period. Some account of the strange animals whose 

 abundance and variety so especially characterised the 

 Secondary period will now be given. 



Ord er Dinosauria 



Some of the best known of these reptiles have been 

 found in our own country, and we will therefore begin with 

 the Iguanodon, of which teeth and bones were found near 

 Maidstone (Kent) by Dr. Mantell in the early part of the 

 last century, but no complete skeletons have been found. 

 A closely allied species from Belgium of the same age (the 

 Wealden) is here figured (Fig. 50). It was about thirty 

 feet long, and is believed to have walked chiefly on its hind 

 feet, and to have fed upon the foliage or fruits of good- 

 sized trees. As shown in the restoration of the animal in 

 its supposed usual attitude when alive (Fig. 51), it would 

 stand about fourteen feet high. The fore-limbs are com- 

 paratively small, terminating in a hand of five fingers, the 

 thumb being represented by a bony claw. The much longer 

 hind legs, however, have feet with only three toes, much 

 resembling those of running birds, and numerous impressions 

 of such feet have been found in rocks of the same age, hence 

 the group to which it belongs has been named Ornithopoda 

 or "bird-footed." From the character of these it seems 



