It seems strange, and it is strange, that while so many hundreds of tracks should have been found in the limited area exposed to view, so few bones have been found--our knowledge of the veritable animals that 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 scattered along the seaside. That part of the Valley of the Connecticut wherein the footprints are found seems to have been a long, narrow estuary running southward 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 bottom a layer of mud. Over and over again this happened, forming 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. [Illustration: Fig. 7.--Footprints of Dinosaurs on the Brownstone of the Connecticut Valley. _From a slab in the museum of Amherst College._] 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, representing various groups of animals. One little point must, however, be borne in mind, that mere size is no sure indication of differences in dealing with reptiles, for these long-lived creatures grow almost continuously throughout life, so that one animal even may have left his footprints over and over in assorted sizes from one end of the valley to the other. The slab shown in Fig. 7 is a remarkably fine example of these Connecticut River footprints; it shows in relief forty-eight tracks of the animal called Brontozoum sillimanium and six of a lesser species. It was quarried near Middletown, in 1778, and for sixty years did duty as a flagstone, fortunately with the face downwards. When taken up for repairs the tracks were discovered, and later on the slab, which measures three by five feet, was transferred to the museum of Amherst College.