NO. 8 GRAND CANYON FOSSIL FOOTPRINTS GILMORE 3 



dance and variety of tracks. Those found were on blocks lying on 

 the hillside, though a few were preserved m situ. That this forma- 

 tion has a large undescribed ichnite fauna is plainly evident, but it is 

 difficult to obtain specimens for study because of the inaccessibility 

 of the perpendicular track-bearing clififs, and because the tracks usually 

 occur in massive blocks of sandstone that do not readily cleave into 

 layers. If adequate study specimens are to be secured, specially trained 

 stone workers with proper equipment must be employed. 



In the Coconino on the south rim of the Grand Canyon, tracks are 

 now known at Dripping Springs on the west, and on the Grand View 

 Trail to the east, an extent of about 29 miles. In the Hermit and 

 Supai, tracks have been found from Hermit Basin on the west to the 

 Yaki Trail on the east, a distance of about 11 miles. That further 

 exploration will greatly extend these ranges is now plainly evident. 

 Tracks have not yet been found in the rocks of the north rim of the 

 Canyon, but it is confidently expected that their discovery there will 

 ' be one of the early announcements.' 



SYSTEMATIC DESCRIPTION OF GENERA AND SPECIES 



Under this heading are included notes and new observations on 

 described genera and species as well as descriptions of a few that are 

 new to the ichnite faunas of the Grand Canyon. They are discussed 

 in the same order as in the preceding papers on this subject, com- 

 mencing with those from the Coconino formation and following suc- 

 cessively with the Hermit, Supai. and Tapeats footprints. 



ICHNITES FROM THE COCONINO FORMATION 



Genus LAOPORUS Lull 



Mention was made in my previous paper ' of the similarity exist- 

 ing between the tracks of Laoporus and those figured by Hickling ^ 

 from the British Permian. Further study and comparison deepens 

 my conviction that these tracks are congeneric. Their close similarity 

 in size, number, relative lengths and arrangement of the digits is 

 clearly indicated in the illustrations (compare figs, i and 2). The 



^ Under date of Dec. 14, 1927, a letter from Mr. G. E. Sturdevant announces 

 the discovery by him of fossil tracks in both the Supai and Coconino forma- 

 tions on the north rim of the Grand Canyon. 



'Smithsonian Misc. Coll., Vol. 80, No. 3, 1927, p. 17, footnote. 



' Manchester Lit. and Plnlos. Soc, Memoirs, Vol. 53, 1909, .^rt. 22. pi. 2, 

 figs. 10 and II. 



