xi 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. 



Or d e r — Dinosau ria 



Some of the best known of these reptiles have been 

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

 he Iguanodon, of which teeth and bones were found near 

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

 Jast century, but no complete skeletons have been found, 

 p. closely allied species from Belgium of the same age (the 

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

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

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

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

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

 '.tand about fourteen feet high. The fore-limbs are com- 

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

 humb being represented by a bony claw. The much longer 

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

 esembling those of running birds, and numerous impressions 

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

 he group to which it belongs has been named Ornithopoda 

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



