People still write from as far away as the Rocky Mountains to ask if the dinosaur footprints beside the Connecticut River are still in place. They are. Anyone may see them in that triangular area between the Boston and Maine tracks and Federal Highway 5 about one-quarter mile north of the entrance to Mountain Park. Marvelous as their preservation from the assaults of man may seem, it is even more amazing that they should have been preserved in rock at all. [Illustration: Pl. 9a. _The dinosaur track preserve at Smith’s Ferry near Holyoke._] [Illustration: Pl. 9b. _Varved clays or calendar beds on river bank south of Hadley._] The footprint beds are shaly sandstones about thirty feet above the Granby tuff—a bed of volcanic ash formed in late Triassic time. They are inclined 15° towards the river, and even the higher strata which form the “Riffles” are footprint-bearing. The sandstones are ripple-marked, and they contain worm trails and a few casts of salt crystals. Some beds have impressions of reeds. The footprints range from half an inch to ten inches in length, and the stride of the larger animals was from five to eight feet. Most of the tracks are headed up the present slope, but a few are going in the opposite direction. The sandstones were laid down as almost horizontal beds of sand which were occasionally covered and rippled by moving but rather shallow water. Rushes and reeds, which have left stray impressions in the rock, grew seasonally in the shallow waters, but in between the periodic rains and floods, the local climate seems to have been quite dry—and probably very warm. The sedimentary record suggests a lowland much like some of the tropical valleys in the West Indies, lying in the rain shadow of adjacent mountains. The large tracks invariably have impressions of three toes. Even a careful search does not disclose the double tracks which would have been left by quadrupeds, and for years the bipedal impressions were called bird tracks. But birds have spurs which leave a mark behind the middle toe; these animals had no spurs and were not birds, but reptiles. Gregarious animals generally follow a leader, and only an occasional individual strays from the beaten path. The tracks at Holyoke suggest that these Triassic reptiles traveled in small herds.