The seventh group contains the impressions of the feet of Saurians or lizards. We have a specimen of quadrupedal marks, with five toes to each foot, about an inch long, which may have been made by these animals. The impressions are small, but very distinct. There are lizards of the present day with five toes, about the size of these impressions; and these may, therefore, be set down as belonging to this order of reptiles. Like a number of the last-named specimens, they are in red shale. * * * * * GROUP EIGHTH. The eighth group is assigned by President Hitchcock to the Chelonian or turtle tribe. The slab bearing impressions of Brontozoum Gracillimum has a mark about fourteen inches long and two wide, which may be attributed to the plastron or breast-plate of the tortoise. On the slab from Turner's Falls there is a longitudinal furrow, which might have been made by the tail of a turtle; and in various of our slabs are impressions which we think belong to this tribe. We shall have occasion to notice hereafter remarkable tracks of these animals in the old red of Morayshire, in Scotland. The most distinct of the traces of chelonians are on the large slab lately obtained for me by President Hitchcock from Greenfield. (_Vide_ Plate.) This interesting slab contains the traces of quadrupeds, various birds, and two trails of chelonians: the largest of these is nearly five feet long, and four inches in diameter. The trail is composed of a number of parallel elevations, comparatively superficial. * * * * * GROUP NINTH. Of the ninth group, containing the marks of Annelidae, Crustacea, and Zoophytes, we have various specimens. The impressions of insects do not seem as yet to have been distinguished on the ancient rocks. There is reason to believe, however, that many of the marks we discover in the rocky beds might have been made by the feet and bodies of large insects; and small species of the same tribes have been found imbedded in, and actually constituting, immense masses of calcareous and siliceous rocks. The tracks of worms are numerous. No doubt these worms drew together a concourse of birds to the shores on which they rolled. On various slabs we find long cylindrical furrows, about the eighth of an inch in diameter, and of different lengths; one of them, in the slab from Dr. Deane, being eight or nine inches long. To these impressions the name of HERPYSTEZOUM, from _herpystes_, _crawling_, has been given. They vary, however, and some of them are very likely to be the tracks of the common earth-worm, or of some species of worm which existed when these rocks were formed. These impressions vary in length and in diameter; some of them are moderately regular, and others irregularly curved.