2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 7/ 



apparent that all varieties to be found at this locality are not repre- 

 sented. It is upon this collection and the one made by Doctor Mer- 

 riam earlier in the year that the present study is based. 



FIELD EXHIBIT OF FOSSIL FOOTPRINTS 



A preliminary survey of the locality on the Hermit Trail showed 

 that the natural conditions were most favorable for the preparation 

 of an exhibit of the tracks in situ. The rather steep slope of the 

 cross-bedded sandstone on whose surface the tracks are impressed 

 stands at an inclination of nearly 30 degrees facing toward the Trail, 

 over which, in the course of a year, hundreds of tourists travel on 

 mule back in making their pilgrimage to the bottom of the canyon. 

 Furthermore, it was found that the upper superimposed layers or 

 laminae scaled ofif in large sheets, thus uncovering the tracks and 

 trails beneath. The preparation of this exhibit required first the re- 

 moval of the overburden of loose dirt and broken rock down to 

 the more compact layers, and then the quarrying ofif of the loose 

 upper laminae until a solid and continuous face covered with foot- 

 prints was reached. In this way a smooth surface 8 feet wide and 

 25 feet long was uncovered, as shown in plate i, figure i. The upper 

 surface of this large slab has a great many tracks and trails leading 

 up the slope, a few passing over and under the more or less horizon- 

 tal strata shown at the top. At the side of the slab and leading up 

 from the trail a flight of stone steps was laid in order to facilitate 

 examination by those interested in a closer inspection of the foot- 

 prints. At the base of this main exhibit, other large slabs lying close 

 to the trail were similarly cleared off (see pi. i, fig. 2), so that 

 there are now several hundred square feet of rock surface forming 

 a permanent exhibit of the various tracks and trails that are to be 

 found here. 



The great antiquity of these footprints, which occur from 900 to 

 1,080 feet below the level of the present rim of the canyon, is clearly 

 demonstrated at this locality. It is obvious that since the day when 

 those animals impressed their feet in what at that time was moist 

 sand, more than 1,000 feet of rock-making materials were piled up 

 in successive strata above them, and this does not take into account 

 many hundreds of feet more that have been eroded off from the 

 present top of the canyon wall. The great length of time required 

 for the cutting away or erosion of the rock to form the deep canyon, 

 and the even longer time necessary for the original deposition of 

 this great vertical mass of stone is, when translated into terms of 



