THEIR LIFE-FORMS. 195 



these saurians were undoubtedly the most notable features 

 of the period. It was indeed the " age of reptiles," when 

 every habitat aquatic, terrestrial, and aerial was occupied ; 

 and every function carnivorous, herbivorous, and insec- 

 tivorous was performed by these creatures. Frog-like, but 

 bulky as an ox, the IdbyrintJiodon squatted on the muddy 

 river-flats ; whale-like, the ichthyosaur paddled through the 

 waters ; iguana-like, but huge as an elephant, the iguano- 

 don browsed on the succulent herbage ; bloodthirsty and 

 mightier still, the deinosaur crouched for his prey in the 

 forest ; while bat-like, under the cliffs and adown the river- 

 banks, fluttered the insectivorous pterodactyls* Every 

 place seems to have been usurped and every function per- 

 formed by these abounding reptilian orders; and this for 

 long ages, while bird-life was gradually coming into force, 

 and mammalian life dawning into existence. 



This bird-life makes its first appearance in the Trias, the 

 surfaces of whose flaggy sandstones are thickly imprinted 

 with their footsteps. These ormtkichnites, or bird-foot- 

 prints, occur in all sizes, from the slender impress of feet 

 like those of the snipe and sandpiper to the heavy implant 

 of others many times bulkier than those of the largest 

 ostrich. Waders and runners, they seem to have frequent- 

 ed the sandy shores of creeks and estuaries which were also 

 the favourite haunts of reptiles, and thus many of these 

 Triassic sandstones are crossed and re-crossed, tracked and 

 re-tracked by footprints whose nature (reptilian or ornithic) 

 it is yet impossible to determine. How wonderful the 

 variety and complexity of the vital record ! how strange 

 that the impression of a passing foot should remain as evi- 

 dence of scenes of life and activity when every other relic 



* Labyrinthodon, from the labyrinthine structure of its teeth ; 

 ickthyosaur, fish-like saurian ; iguanodon, having teeth like the existing 

 iguana ; deinosaur, terrible saurian ; pterodactyle, finger- winged or flying 

 reptile. 



