TRIASSIC ERA. 127 



worms must have tracked and burrowed in the open sands, 

 shell-fish and Crustacea crawled and pattered on the muddy 

 beach, and reptiles, birds, and mammals footed the tidal 

 silt of bays and estuaries. Wherever these materials were 

 of sufficient consistence, and exposed during a long tidal 

 ebb to the desiccating effects of the sun, there the impres- 

 sions would be retained, and act as a mould for the recep- 

 tion of the next influx of mud. The mould and its cast, 

 covered over by repeated sediments, are thus preserved 

 for ever, bearing every outline of form and minutiae of 

 structural surface, according to the nature of the deposit 

 that received the living impression. Over these old trias- 

 sic shores numerous birds and reptiles waded and wandered, 

 now wheeling in sport, now fleeing in fear, and anon steal- 

 ing stealthily on their devoted victims. JS r ot a bird-bone 

 has yet been discovered in the sediments that bear these 

 fossil footprints,""" and yet so characteristic is the foot of 

 the bird (the number and disposition of its joints, and the 

 corrugations of its skin), that palaeontology rests satisfied 

 in their existence as fully as though their skeletons were 

 there to indicate their habits and dimensions. In the case 

 of mammalian life the evidence, though scantier, is much 



Dr Hitchcock has already enumerated 123 species viz., marsupialoid 

 animals, 5 ; birds, 31 ; ornithoid reptiles, or reptiles walking on their 

 hind feet, 12; lizards, 17; batrachians or frog-like reptiles, 16; chelo- 

 nians or turtles, 8 ; fishes, 4 ; crustaceans, myriapods, and insects, 17 ; 

 and annelids, 10. 



* In 1860, a block of red sandstone, containing the impressions of 

 bones, apparently of ornithic character, was discovered in America, and 

 described by Professor W. B. Rogers to the Natural History Society of 

 Boston. This block was not, however, found in situ, but among other 

 building stones which were said to have been brought from Portland 

 Quarry, in the valley of the Connecticut. The evidence is thus some- 

 what invalidated, though Professor Rogers seems confident as to its 

 mesozoic or new red sandstone origin. This specimen, unique in the 

 mean time, gives hope of the speedy discovery of other and more legible 

 fragments. 



