40 ANIMALS OF THE PAST 
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 scattered along the sea- 
side. : 
That part of the Valley of the Connecticut 
wherein the footprints are found seems to have 
been a long, narrow estuary running south- 
ward. from Turner’s Falls, Mass., where the 
tracks are most abundant and. most clear. 
The topography was such that this 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 bot- 
tom a layer of mud. Over and over again this 
happened, forming layer upon layer of what is 
now stone, sometimes the lapse of time be- 
