FOOTPRINTS IN THE ROCKS. 431 



The first scientific publication concerning fossil foot-marks is con- 

 tained in the Transactions of the Royal Society of Edinburgh in 1828. 

 Six years later, Prof. Kaup described the tracks of the C heir other turn, 

 a beast toith hands, upon Triassic sandstones in Germany. The animal 

 must have equalled an ox in size, with hind-feet shaped like the human 

 hand, which were about three times larger than the front-feet. He is 

 generally supposed to have been a batrachian. The earliest descrip- 

 tion of the American ichnites appeared in 1836. 



The Triassic formations on the Atlantic slope are disposed in long 

 and narrow areas. These may correspond with the spaces occupied by 

 estuaries before the deposition of the strata. We may suppose that 

 an arm of the sea extended northerly from Long Island Sound to New 

 Hampshire along the Connecticut Valley, possibly connecting, beneath 

 the Sound and North River, with a similar estuary running southerly 

 to Virginia. If we transport ourselves in imagination to these ancient 

 shores, we shall see that the animals left their hiding-places and were 

 traversing the soft mud laid bare by the ebbing tide, in search of food. 

 The heat of a tropical sun quickly hardens the mud, so that the return- 

 ing tide, in bringing a fresh deposit of mud, does not wash away the 

 impressions already made on the lower layer, but carefully covers them 

 over. The imprints have, therefore, become a species of mould into 

 which another muddy fluid is poured, and by hardening is made to 

 copy the foot-mark like a plaster cast. Hence, when artificially cleared, 

 no matter how many ages subsequently, the strata will present to 

 view the depressed print below and the cast of the foot above, both as 

 perfect as the respective fineness of the mud and its degree of rapid 

 induration by the sun will permit. This process of deposition may 

 have been repeated, just as it may now be studied, in the Bay of 

 Fundy, till the whole estuary was filled up, partly with fine mud and 

 clay, partly with beds of sand and gravel, all more or less marked by 

 the feet of animals, interspersed with volcanic beds of lava, tufa, and 

 conglomerate, and rare chemical deposits of carbonate of lime, salt, 

 and gypsum. 



The Ichnozoa, or the animals who made the tracks on stones in 

 Triassic times, may be referred to several prominent divisions of the 

 animal kingdom. The first, and highest in the scale, is a group of five 

 species, remotely allied to marsupials, which, from their osseous remains 

 found in Europe, we know must have flourished in that period. The 

 most characteristic is a five-toed quadruped, about the size of a lion, 

 whose foot is not unlike that of a carnivorous animal. The others had 

 unequal feet, larger behind and smaller in front. The most important 

 groups are those referred to birds, embracing thirty-four species ; 

 equally divided between those related to the ostrich family thick- 

 toed and those with long, slender toes, like the crane and heron. 

 These are the impressions chiefly relied upon to prove the ornithic 

 character of any of the Ichnozoa, as they show distinctly the phalangeal 



