^2. SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



close resemblance to those of the hindfoot, in size, shape, and relative 

 positions to one another. The presence of lateral toes is suggested 

 by a toe scratch on the inner side of one impression, and on the outer 

 side of this same jirint the sand shows disturbance as if a fifth toe 

 was present, but one cannot be sure and the other forefoot tracks are 

 not sufficiently well impressed to give any additional evidence on this 

 point. The sole is imperfectly impressed and this fact may account 

 for the faintness of the evidence relating to the lateral digits. Width 

 of three digits 48 mm., same as those of the hindfoot. Lengths: 

 II = 22.5 mm. ; III = 26 mm. ; IV = 26 mm. 



The variation in the different tracks is clearly indicated in figure 37. 



A second occurrence of this genus and species seems to be indicated 

 by a comparison of figure 2, plate 2, with the trackway above de- 

 scribed. In the illustration the three-toed frontfoot may be seen in 

 its proper position in front of the hindfoot, which, except for the 

 lack of a fifth digit, agrees in all essentials with the type of the 

 present genus and species. If this long range identification is correct 

 it shows the presence of this form at the Yaki locality some seven or 

 eight miles distant in an air line from the type locality. 



SUMMARY 



The study of these fossil footprints has resulted in the establish- 

 ment of adequate ichnite faunas for the Coconino and Hermit for- 

 mations and the beginning of a fauna for the older Supai. The 

 various forms described are, with few exceptions, based upon track- 

 ways showing impressions of all four feet, a procedure that should 

 give the minimum trouble in the identification of specimens that may 

 be subsequently discovered. The faunal lists could have been con- 

 siderably augmented had it seemed expedient to describe inferior 

 material, but a more conservative course was adhered to. 



Comparison of these three faunas shows them to be absolutely 

 distinct from one another as not a single genus has yet been found 

 common to any two of the formations. In so far as the Hermit is 

 concerned, this fact occasions no particular surprise, even though the 

 difference in geological level be disregarded, for the environmental 

 conditions were such as to lead one to expect an entirely different 

 assemblage of animal life than would be found in either the Coconino 

 or Supai. The muddy character of the sediments with sun-cracked 

 surfaces, with associated ferns and other water-loving plants are all 

 indicative of the low lying nature of the region at the time these ani- 

 mals inhabited it. The many amphibian-like footprints, and tracks 



