IMPRESSIONS OF THE PAST 27 



made the tracks being a blank. A few examples have, 

 it is true, been found, but these are only a tithe of 

 those known to have existed ; while of the great animals 

 that strode along the shore, leaving tracks fifteen inches 

 long and a yard apart pressed deeply into the hard sand, 

 not a bone remains. The probability is that the strata 

 containing their bones lie out to sea, whither their bodies 

 were carried by tides and currents, and that we may 

 never see more than the few fragments that were scat- 

 tered along the sea-side. 



That part of the Valley of the Connecticut wherein 

 the footprints are found was either part of a river bed or 

 of a long, narrow estuary running southward from 

 Turner's Falls, Mass., where the tracks are most abun- 

 dant and most clear. The topography was such that 

 this river, or estuary, was subject to sudden and great 

 fluctuations of the water-level, large tracts of shore 

 being now left dry to bake in the sun, and again covered 

 by turbid water which deposited on the bottom a layer 

 of mud. Over and over again this happened, just as to- 

 day it occurs along such streams as the Potomac, form- 

 ing layer upon layer of what is now stone, sometimes the 

 lapse of time between the deposits being so short that 

 the tracks of the big Dinosaurs extend through several 

 sheets of stone ; while again there was a period of drouth 

 when the shore became so dry and firm as to retain but a 

 single shallow impression. 



Something of the wealth of animal life that roamed 

 about this estuary may be gathered from the number of 

 different footprints recorded on the sands, and these are 

 so many and so varied that Professor Hitchcock in two 

 extensive reports enumerated over 150 species, repre- 

 senting various groups of animals. One little point 

 must, however, be borne in mind, that mere size is no 

 sure indication of differences in dealing Avith reptiles, 



