NO. 9 GRAND CANYON FOSSIL FOOTPRINTS — GILMORE 35 



Type locality. — Hermit Trail, Hermit Basin, Grand Canyon Na- 

 tional Park, Arizona. 



Geological occurrence. — Coconino sandstone (150 feet above base), 

 Permian.' 



In plate 12, figure 2, is shown a photographic reproduction of two 

 parallel lines of footprints which clearly represent the trail of some 

 animal, but which, in most of its details, is quite obscure. The one 

 distinctive feature is the presence of a median row of suboval depres- 

 sions regularly spaced and for half the length of the trail deeply im- 

 pressed ; on the other half they are either shown faintly or missing 

 entirely. The width of the trackway is 22.4 millimeters ; distance be- 

 tween depressions of median row averages about 15 millimeters, 

 which also represents the length of stride. Whether these median 

 pits were formed by a caudal appendage or by a descending ventral 

 protuberance on the body is of course impossible to determine. It 

 would seem most logical to regard them as having been made by a 

 short, stubby tail. 



The direction of movement is shown on the forward border of the 

 pits by the drag made by the appendage causing the oval depressions, 

 as contrasted with the more perpendicular posterior side of the im- 

 print. 



The trail is quite different from any other in the collection, and I 

 find nothing like it described. That it was made by some invertebrate 

 there is little doubt, but no clue has been found as to the particular 

 animal. 



The specific name is in honor of Dr. Marcus Benjamin, who for 

 many years has so ably edited the scientific publications of the 

 United States National Museum. 



SUMMARY 



That both vertebrate and invertebrate animals are present in this 

 collection of footprints is certain, but with the exception of the 

 classes Reptilia and Amphibia among the former, quite certainly rep- 

 resented by the tracks designated Dolichopodus tctradactylns and 

 Baropcsia cakini respectively, it was found impossible to assign the 

 other forms to their proper class with any degree of assurance. 



No skeletal remains are known from the Coconino sandstone and 

 consequently no direct clue is ofl:'ered as to the makers of any of these 

 tracks. A study was made of the Permian vertebrate fauna found 

 in the adjacent regions in the hope that forms might be found whose 

 structure would indicate responsibility for some of the imprints. 

 This search was not entirely in vain, for in the Permian Aracoscclis 



