351 Sehuchert — Carboniferous of Grand Canyon of Arizona. 



prisms of intcrbedded sun-cracked shales, are often rain- 

 pitted, and further marked by the feet impressions of 

 fresh-water amphibians described elsewhere in this num- 

 ber of the Journal by Professor Lull as Megapezia (?) 

 coloradensis and Exocampe (?) delicatula. Some of the 

 tracks are distinct impressions of the feet and others are 

 mere strokes of the toes. In these same beds also occur 

 plant remains in very fragmentary condition which were 

 badly macerated and coated with a slime of red mud dur- 

 ing their entombment. They are therefore difficult to 

 determine, but after much effort Doctor David White 

 tentatively identified them as Callipteris sp., cf. C. con- 

 flict, Walchia cf. W. gracilis, Gigantopteris, and cf. 

 Sphenophyllum. 



Age of Upper Supai. — The amphibian tracks of Mega- 

 pezia (?) coloradensis Lull compares with forms of this 

 genus found in the "Lower Carboniferous" (presumably 

 Pennsylvanian) of Parrsboro, Nova Scotia. The other 

 track, which he names Exocampe (?) delicatula, resem- 

 bles closely the genus of the Connecticut Triassic but as 

 it ' ' is a generalized track which almost any small amphib- 

 ian . . . might make" the fossil has little stratigraphic 

 significance. In fact, these tracks can not be depended 

 on more than that they seem to indicate Pennsylva- 

 nian age. 



The plants listed above and found associated with the 

 tracks in the Upper Supai led "White in his letter to the 

 writer dated June 27, 1916, to the following conclusions : 



"The condition of preservation of the fragments is so bad 

 that caution is necessary in basing conclusions of any kind on 

 the material submitted. However, the presence of Gigantop- 

 teris, Walchia, and probably of Callipteris, if my tentative 

 generic identification of the latter is correct, points to Lower 

 Permian age of the flora ... In any event, it appears probable 

 that the flora, when it is better known, will be found to indicate 

 a level not below the highest stage of the Pennsylvanian." 



It is of interest to note here that Walchia has also been 

 found in much higher beds farther to the east in Arizona. 

 Above the thinned Kaibab is the Moenkopi formation of 

 red shales and sandstones in which Gregory reports the 

 presence "on the rim of the Little Colorado Canyon" of 

 marine molluscs of Permian age, and, farther east near 



°Op. eit., p. 31. 



