NO. 8 



GRAND CANYON FOSSIL FOOTPRINTS GILMORE 



13 



Some of the imprints are tridactyle, others didactyle. The toes are 

 usually sharply pointed and widely divergent. These tracks vary 

 from 14 to 16 mm. in length and from 9 to 12 mm. in width. They 



Fig. 6. — Invertebrate trail from Supai formation. No. 11,693, 

 U. S. N. M. About 2 natural size. 



give every evidence of having been made by an invertebrate animal to 

 whose identity we have no clue at this time. It is anticipated that 

 sooner or later well-defined trails of this animal will be discovered. 



