NO. 3 GRAND CANYON FOSSIL FOOTPRINTS GILMORE 73 



left by crawling, short-legged creatures who dragged their tails and 

 bellies in the mud appear typical of such an environment. 



The Coconino fauna is nearly doubled in the number of known 

 species but the facies of the fauna remains as stated in a previous 

 paper — " Carboniferous in aspect, as shown by the relatively small 

 size of the animals, all of which are quadrupedal, as contrasted with 

 the considerable number of very large forms and many three-toed 

 bipedal animals of the Triassic." Taken as a whole, this fauna now 

 consists of 15 genera and 22 species and seems to have closer relation- 

 ships to the ichnite fauna from the Middle Coal Measures of Kansas, 

 described by Marsh than to the more extensive fauna from the Coal 

 Measures of Nova Scotia made known by Dawson and Matthew. 



On the other hand the Hermit fauna has its closest affinities with 

 that from Nova Scotia, for of the eight genera now known, four are 

 common to both and the facies of the two faunas taken as a whole 

 shows striking resemblances. That similar environmental conditions 

 prevailed in these two widely separated localities is indicated by the 

 similarity in the character of the sediments in which the imprints 

 occur. 



The Supai fauna, known at present by three genera and as many 

 species, shows no close relationships wi<:h tracks from other localities, 

 although it may be said to be Carboniferous in aspect. It apparently 

 represents an ichnite fauna new to North America and consequently 

 has little correlative value at this time. 



Aside from the trails of invertebrate animals found all others were 

 made by quadrupedal creatures, but only a comparatively few give 

 any certain clue as to whether they pertain to the Reptilia or 

 Amphibia. 



Animals having a digital formula of 5 and 5 predominate in the 

 Hermit, while those having a lesser number are more abundant in the 

 Coconino. Whether this fact has any significance remains to be 

 determined. Search of the literature shows that all Permian animals 

 in which the foot structure is known have tive digits in both manus 

 and pes and of the Coal Measures Amphibia none shows fewer than 

 four digits in the manus and five in the pes. It would seem therefore 

 either that none of the Permian animals known from their skeletons 

 may be considered as the makers of the three and four toed tracks, or 

 else certain digits consistently fail to leave their impressions. 



In an attempt to identify some of the known Permian vertebrates 

 as being responsible for certain of these tracks, tracings were made of 

 all of the available fore- and hindfeet of animals of that period, in 

 order that these tracings might be placed directly upon the tracks. 



