Horizon and locality: Osage limestone (Coal Measures), near Osage City, Kansas. In 1894 Professor Marsh described a collection of footprints which he had secured from Professor B. F. Mudge, of Manhattan, Kansas, who had collected them in Osage County, Kansas, in a rock quarry, having purchased a large quantity of rock from the quarrymen for that purpose. A preliminary note by Mudge (490) was published in the Transactions of the Kansas Academy of Science and later copied in the American Journal of Science. Professor Marsh's description (406) of the remains is as follows: "The impressions are well preserved in a calcareous shale, which separates readily into thin slabs, each representing a surface of the beach at the time the footprints were made upon it. A few shells in the shale are sufficient to prove that the formation is marine (no shells are evident in the slab at the Museum of the University of Kansas, but the slab is quite arenaceous). Trails of annelids, or perhaps of other invertebrates, are seen on some of the surfaces. The footprints of vertebrate animals, however, are of paramount importance, and the large number and variety of these here recorded on a single surface, if they could be rightly interpreted, would form an interesting chapter of land vertebrate life in the Carboniferous, about which so little is at present known." [Illustration: Fig. 43.--Footprints of _Dromopus agilis_ Marsh, from the Coal Measures of Osage County, Kansas. Original slab in University of Kansas Museum. Greatly reduced.] Professor Marsh's description of _Dromopus agilis_ is as follows: "The third series of footprints is of special interest, and indicates an animal very distinct from the two already described. The diagram represents the impression of the phalanges sufficiently in detail to indicate (406) their number and general form. A striking feature in the fore and hind feet of this animal was the long, slender digits terminated by sharp claws. Another point of interest, as recorded in the footprints, is that the animal in walking swung the hind feet outward, and so near the ground that the ends of the longer toes sometimes made trails in the mud, marking accurately the sweep of the foot. This would seem to indicate a comparatively short hind leg, rather than the long, slender one which the footprints themselves naturally suggest. "The animal which made these interesting footprints was probably a Lacertilian rather than an Amphibian, but there is also a possibility that it was a primitive Dinosaur." Further on Professor Marsh remarks (p. 84):