644 



C. L. DAKE 



The writer opposes the conclusions of Emery and Lee on the 

 following grounds: 



1. There are, at several other horizons in the La Plata, lime- 

 stone lenses of character almost absolutely similar to the Todilto 

 with which, on lithologic grounds alone, these fossiliferous beds 

 might quite as well be correlated. 



2. The limestones of the Todilto and all the other limestones of 

 the La Plata are apparently absolutely non-fossiliferous, while these 

 beds are packed with fossils. 



3. As described by Gregory the Todilto is not a gypsum- 

 bearing formation. On the other hand, the McElmo, where 



.* 





Photo by L.y. Z.'lUr 



Fig. 10. — McElmo gypsiferous sandstone and shale, Water Pocket Canyon, 

 Utah. These beds lie above the gypsum beds in dispute, and are considered Navajo 

 by Emery. 



definitely known to overlie true Navajo, though it does not carry 

 gypsum beds, is repeatedly reported as highly gypsiferous. Gypsum 

 is also an abundant constituent of the fossiliferous series in question. 

 In a personal letter Dr. Stanton called the writer's attention to the 

 fact that the section in question differed from typical McElmo in 

 its numerous gypsum beds. The criticism applies even more 

 positively in comparisons with the non-gypsiferous Todilto. If, as 

 Lee suggests, the Todilto represents the fringe of the marine 

 fossiliferous beds, along embayments where conditions were 

 unfavorable to marine life, the gypsum-forming conditions should 

 surely be presumed to persist into the Todilto area, a feature of the 

 Todilto that Gregory does not mention. 



